EI 10-6 TorrCI 01-20 Torr

EI vs CI

Primary ionsShort mean free paths(~ 2 x 10-4 mm)

R (excess)

Reactant gas

(Secondary ions)

Generally ions with an even number of electrons (cations RH+) are more stable than ions with an odd number of electrons (radical cations) like A+ primary ions

The secondary ions are strong Lewis acid therefore donate a proton Less usually a hydrogen ion is abstracted from M

Adduct ions

Depending on the acidity of the reactant gas and the basicity of the sample molecules hydrogen transfer may not occur and instead the secondary ions react with molecules (M) to give adduct ions rather than protonated molecules

M + NH4+ [M + NH4+]+

M + C2H5+ [M + C2H5

+]+

M + C3H7+ [M + C3H7

+]+

In general quasi-molecule ions obtained by chemical ionization have greater relative Abundances than molecular ions obtained by EI [M + H]+ is more stable than M+ because the former is produced with a little excess of internal energy and because it isEven-electron species unlike the radical cations (M+) formed by EI

[M + H]+

M+

After chemical ionization C-C bonds tend to cleave only if the product of the dissociation are particularly stable Often the carbon skeleton remains intact and cleavage is restricted the bonds of functional groups such as C-O C-S and C-N bonds

Chemical Ionization and Reagent gasesbull Degree of fragmentation can be controlled by changing reagent gases because

ndash The amount of excess of energy imparted on an [M + H]+ ion on its formation depends on the relative affinities of the conjugate base of the reactant ion (CH4 NH3 and so on) and the compound M

bull Decrease in PA (proton affinity) of the conjugate base (or increase in acidity of the reactant gas ion) causes increase in fragmentation because more energy is transferred to them during their formation

bull Acidity increase in the order

NH4+ lt C4H9

+ lt C2H5+ lt CH3

+ lt H3+

bull The degree of fragmentation caused by these common reactant gas ions increase in the same order

CH3+ and H3

+ For structure elucidation

NH4+ and C4H9

+ For confirmation of relative molecular mass of a more fragile molecule

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

EI vs CI

Primary ionsShort mean free paths(~ 2 x 10-4 mm)

R (excess)

Reactant gas

(Secondary ions)

Generally ions with an even number of electrons (cations RH+) are more stable than ions with an odd number of electrons (radical cations) like A+ primary ions

The secondary ions are strong Lewis acid therefore donate a proton Less usually a hydrogen ion is abstracted from M

Adduct ions

Depending on the acidity of the reactant gas and the basicity of the sample molecules hydrogen transfer may not occur and instead the secondary ions react with molecules (M) to give adduct ions rather than protonated molecules

M + NH4+ [M + NH4+]+

M + C2H5+ [M + C2H5

+]+

M + C3H7+ [M + C3H7

+]+

In general quasi-molecule ions obtained by chemical ionization have greater relative Abundances than molecular ions obtained by EI [M + H]+ is more stable than M+ because the former is produced with a little excess of internal energy and because it isEven-electron species unlike the radical cations (M+) formed by EI

[M + H]+

M+

After chemical ionization C-C bonds tend to cleave only if the product of the dissociation are particularly stable Often the carbon skeleton remains intact and cleavage is restricted the bonds of functional groups such as C-O C-S and C-N bonds

Chemical Ionization and Reagent gasesbull Degree of fragmentation can be controlled by changing reagent gases because

ndash The amount of excess of energy imparted on an [M + H]+ ion on its formation depends on the relative affinities of the conjugate base of the reactant ion (CH4 NH3 and so on) and the compound M

bull Decrease in PA (proton affinity) of the conjugate base (or increase in acidity of the reactant gas ion) causes increase in fragmentation because more energy is transferred to them during their formation

bull Acidity increase in the order

NH4+ lt C4H9

+ lt C2H5+ lt CH3

+ lt H3+

bull The degree of fragmentation caused by these common reactant gas ions increase in the same order

CH3+ and H3

+ For structure elucidation

NH4+ and C4H9

+ For confirmation of relative molecular mass of a more fragile molecule

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

The secondary ions are strong Lewis acid therefore donate a proton Less usually a hydrogen ion is abstracted from M

Adduct ions

Depending on the acidity of the reactant gas and the basicity of the sample molecules hydrogen transfer may not occur and instead the secondary ions react with molecules (M) to give adduct ions rather than protonated molecules

M + NH4+ [M + NH4+]+

M + C2H5+ [M + C2H5

+]+

M + C3H7+ [M + C3H7

+]+

In general quasi-molecule ions obtained by chemical ionization have greater relative Abundances than molecular ions obtained by EI [M + H]+ is more stable than M+ because the former is produced with a little excess of internal energy and because it isEven-electron species unlike the radical cations (M+) formed by EI

[M + H]+

M+

After chemical ionization C-C bonds tend to cleave only if the product of the dissociation are particularly stable Often the carbon skeleton remains intact and cleavage is restricted the bonds of functional groups such as C-O C-S and C-N bonds

Chemical Ionization and Reagent gasesbull Degree of fragmentation can be controlled by changing reagent gases because

ndash The amount of excess of energy imparted on an [M + H]+ ion on its formation depends on the relative affinities of the conjugate base of the reactant ion (CH4 NH3 and so on) and the compound M

bull Decrease in PA (proton affinity) of the conjugate base (or increase in acidity of the reactant gas ion) causes increase in fragmentation because more energy is transferred to them during their formation

bull Acidity increase in the order

NH4+ lt C4H9

+ lt C2H5+ lt CH3

+ lt H3+

bull The degree of fragmentation caused by these common reactant gas ions increase in the same order

CH3+ and H3

+ For structure elucidation

NH4+ and C4H9

+ For confirmation of relative molecular mass of a more fragile molecule

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Adduct ions

Depending on the acidity of the reactant gas and the basicity of the sample molecules hydrogen transfer may not occur and instead the secondary ions react with molecules (M) to give adduct ions rather than protonated molecules

M + NH4+ [M + NH4+]+

M + C2H5+ [M + C2H5

+]+

M + C3H7+ [M + C3H7

+]+

In general quasi-molecule ions obtained by chemical ionization have greater relative Abundances than molecular ions obtained by EI [M + H]+ is more stable than M+ because the former is produced with a little excess of internal energy and because it isEven-electron species unlike the radical cations (M+) formed by EI

[M + H]+

M+

After chemical ionization C-C bonds tend to cleave only if the product of the dissociation are particularly stable Often the carbon skeleton remains intact and cleavage is restricted the bonds of functional groups such as C-O C-S and C-N bonds

Chemical Ionization and Reagent gasesbull Degree of fragmentation can be controlled by changing reagent gases because

ndash The amount of excess of energy imparted on an [M + H]+ ion on its formation depends on the relative affinities of the conjugate base of the reactant ion (CH4 NH3 and so on) and the compound M

bull Decrease in PA (proton affinity) of the conjugate base (or increase in acidity of the reactant gas ion) causes increase in fragmentation because more energy is transferred to them during their formation

bull Acidity increase in the order

NH4+ lt C4H9

+ lt C2H5+ lt CH3

+ lt H3+

bull The degree of fragmentation caused by these common reactant gas ions increase in the same order

CH3+ and H3

+ For structure elucidation

NH4+ and C4H9

+ For confirmation of relative molecular mass of a more fragile molecule

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

In general quasi-molecule ions obtained by chemical ionization have greater relative Abundances than molecular ions obtained by EI [M + H]+ is more stable than M+ because the former is produced with a little excess of internal energy and because it isEven-electron species unlike the radical cations (M+) formed by EI

[M + H]+

M+

After chemical ionization C-C bonds tend to cleave only if the product of the dissociation are particularly stable Often the carbon skeleton remains intact and cleavage is restricted the bonds of functional groups such as C-O C-S and C-N bonds

Chemical Ionization and Reagent gasesbull Degree of fragmentation can be controlled by changing reagent gases because

ndash The amount of excess of energy imparted on an [M + H]+ ion on its formation depends on the relative affinities of the conjugate base of the reactant ion (CH4 NH3 and so on) and the compound M

bull Decrease in PA (proton affinity) of the conjugate base (or increase in acidity of the reactant gas ion) causes increase in fragmentation because more energy is transferred to them during their formation

bull Acidity increase in the order

NH4+ lt C4H9

+ lt C2H5+ lt CH3

+ lt H3+

bull The degree of fragmentation caused by these common reactant gas ions increase in the same order

CH3+ and H3

+ For structure elucidation

NH4+ and C4H9

+ For confirmation of relative molecular mass of a more fragile molecule

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Chemical Ionization and Reagent gasesbull Degree of fragmentation can be controlled by changing reagent gases because

ndash The amount of excess of energy imparted on an [M + H]+ ion on its formation depends on the relative affinities of the conjugate base of the reactant ion (CH4 NH3 and so on) and the compound M

bull Decrease in PA (proton affinity) of the conjugate base (or increase in acidity of the reactant gas ion) causes increase in fragmentation because more energy is transferred to them during their formation

bull Acidity increase in the order

NH4+ lt C4H9

+ lt C2H5+ lt CH3

+ lt H3+

bull The degree of fragmentation caused by these common reactant gas ions increase in the same order

CH3+ and H3

+ For structure elucidation

NH4+ and C4H9

+ For confirmation of relative molecular mass of a more fragile molecule

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

bull In EI [M + H]+ ion can be formed if the sample pressure becomes too high in the source

M+ + M [M + H]+ + [M ndashH]

This process is frequently observed when 1) the normal abundance of molecular ions M+ in EI spectra is low 2) the molecule of interest contains a site of high PA (like amino

acid)3) Self-CI can be reduced or eliminated by analyzing a smaller

amount of sample

ldquoSelf-CIrdquo

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

a) Proton Transfer b) Nucleophillic Addition c) Hydrogen Abstraction

Chemical ionization

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Methanegood for most organic compounds usually produces [M+H]+ [M+CH3]+ adducts adducts are not always abundant extensive fragmentation

Isobutaneusually produces [M+H]+ [M+C4H9]+ adducts and some fragmentation adducts are relatively more abundant than for methane CI not as universal as methane

Ammoniafragmentation virtually absent polar compounds produce [M+NH4]+ adducts basic compounds produce [M+H]+ adducts non-polar and non-basic compounds are not ionized

Chemical ionization Common Reagent Gases

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Methane Chemical Ionization

CH4+ will also fragment (although not a major pathway)

CH4+ CH3

+ + H

CH4+ CH2

+ + H2

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

CH3+ + CH4 C2H5

+ + H2

CH2+ + CH4 C2H3

+ + H2 + HC2H3

+ CH4 C3H5+ + H2

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

bull If sample M is a saturated hydrocarbon RH

RH + CH5+ R+ + CH4 + H2 (hydrogen abstraction)

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Isobutane Chemical Ionization

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Isobutene Chemical Ionization

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

bull NH3+ + NH3 NH4

+ + NH2

bull NH4+ + NH3 (NH4 + NH3)+

bull RNH2 + NH4+ RNH3

+ + NH3 (for basic compounds)

bull R + NH4+ RNH4

+ (no or little basic character)

bull No efficient ionization for saturated hydrocarbons

Ammonia Chemical Ionization

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Ammonia Chemical Ionization

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Charge Transfer (exchange) Chemical Ionization

bull Reactant gas ions are formed from monoatomic species like argon

Ar + e Ar+

Ar+ + M Ar + (M+)

bull Ar does not have vibrational degree of freedombull Excess of energy after ionization is 15755 eVbull Excess of energy will transfer to Mbull Excess of after M is ionized (15775 ndash I) eVbull I is ionization energy of Mbull M has vibrational degree of freedom and will fragmentbull Knowledge of the precise amount of excess of energy given to Mbull Sometimes can selectively ionize a mixture of compounds

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Chemical ionization Negative Ions

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Ionization Nomenclature

Electron attachmentA resonance process whereby an electron is incorporated into an atomic or molecular orbital of an atom or molecule

A + e- A -

Chargendashexchange (charge transfer) ionizationOccurs when an ionatom or ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species without dissociation of either

A++ B A + B+ Dissociative charge transferOccurs when an ionmolecule reaction takes place in which the charge on the ion is transferred to the neutral species The new ion then dissociates to one or more fragment ions

A++ B A + B+ A + (F1+ F2+ Fn+)Ionndashpair formationAn ionization process in which a positive fragment ion and a negative fragment ion are the only products

A B A+ + B-

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26

Ionization Nomenclature

Electron ionization (Electron Impact)

Ionization of any species by electrons The process may be written

M + e- M+ + 2e-

M + e- M -

Photondashionization

Ionization of any species by photon (hv)

M + hv M+ + e-

Electrons and photons do not lsquoimpactrsquo on molecules or atoms They interact with them in ways that result in various electronic excitations including ionization

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Adduct ions
• Slide 10
• Chemical Ionization and Reagent gases
• ldquoSelf-CIrdquo
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Isobutane Chemical Ionization
• Isobutene Chemical Ionization
• Ammonia Chemical Ionization
• Slide 21
• Charge Transfer (exchange) Chemical Ionization
• Slide 23
• Slide 24
• Ionization Nomenclature
• Slide 26