determinations of inorganic anions and organic acids ….pdf · determinations of inorganic anions...

Determinations of Inorganic Anions and Organic Acids in Beverages Using Suppressed Conductivity and Charge DetectionTerri Christison, Linda Lopez Thermo Fisher Scientific, Sunnyvale, CA, USA

2 Determinations of Inorganic Anions and Organic Acids in Beverages Using Suppressed Conductivity and Charge Detection

Determinations of Inorganic Anions and Organic Acids in Beverages Using Suppressed Conductivity and Charge DetectionTerri Christison, Linda LopezThermo Fisher Scientific, Sunnyvale, CA, USA

ConclusionThe QD Charge Detector offered on the Dionex ICS-4000HPIC system improves sample analysis and reporting reliability by:

Detecting peaks previously not detected by CD.

Identifying doubly and triply charged ions from the proportionally higher response than the singly charged ions.

Providing more linear response and proportionally higher responses for weakly ionized than strongly ionized compounds by CD

Detecting co-eluting peaks by the proportionally higher responses of multi-charged ions than singly charged ions.

References1. Srinivasan, K., PhD. High Pressure Ion

Chromatography Charge Detection, webinar, October 2012. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

2. Basumallick, L., PhD. Analysis of Carbohydrates & Organic Acids Using Capillary IC Methods, webinar, February 2013. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

3. Verma, M. What is Charge Detection? White paper, WP70585_E 03/13S. Thermo Fisher Scientific, Sunnyvale, CA, 2013.

OverviewPurpose: To demonstrate the advantages of using QD Charge detection for Ion Chromatography (IC).

Methods: Inorganic anions and organic acids were separated on a high-capacity 4-µm particle Thermo Scientific™ Dionex™ IonPac™ AS11-HC-4µm capillary column and detected with suppressed conductivity in series with charge detection. Analysis was facilitated by a high-pressure capillary IC system.

Results: Very high efficient separations at > 3500 psi system pressures were demonstrated on the Dionex IonPac AS11-HC-4µm on a dedicated capillary IC system. The QD charge detector shows comparably higher charge response for organic acids than for chloride and sulfate and can detect other peaks previously not detected by conductivity (CD). CD/QD ratios were used to assess peak purity, thereby improving reporting accuracy.

IntroductionDeterminations of organic acid profiles in fruit juices are important in the beverage industry to ascertain product quality and to meet labeling requirements for food products. Ion chromatography with suppressed conductivity is the ideal analytical method for ionic analytes. However organic acids which are weakly ionized can exhibit lower conductivity responses versus concentration than strongly ionized anions, such as chloride and sulfate. However, the new Thermo Scientific Dionex QD Charge Detector promotes complete dissociation of even weakly ionized compounds.

ResultsQD Charge DetectionA charge detector (QD) is a constant voltage membrane device that maintains a specified potential at the anode and cathode (Figure 3).1 As the sample passes through the detector, the ions are drawn through the ion-exchange membranes, drawing a current to balance the charge. This results in a response proportional to the charge state and a significantly higher response for weakly ionized compounds than would be obtained with CD.

Figure 5 shows increased linear response for weakly ionized analytes with charge detection.1

Data AnalysisThermo Scientific™ Dionex™ Chromeleon™ Chromatography Data System (CDS) software

All trademarks are the property of Thermo Fisher Scientific and its subsidiaries.

This information is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others.

FIGURE 8. Comparing CD to QD in a diluted orange juice sample to identify co-elution and detect additional peaks

FIGURE 3. Mechanisms of Dionex Charge Detection.

MethodsSample PreparationCommercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.

Ion Chromatography Instrumentation (Figure 1)• Thermo Scientific™ Dionex™ ICS-4000 HPIC™ dedicated

capillary IC system with•Dionex IonPac ATC-500 trap column• Thermo Scientific Dionex Conductivity Detection (CD)

detector• Dionex QD Charge Detector Cell (QDC) • Thermo Scientific Dionex AS-AP Autosampler

.

Column set: Dionex IonPac AS11-HC-4µm, guard and separation columns, 0.4 mm

Eluent Source: Thermo Scientific Dionex EGC-KOH capillary cartridge with Thermo Scientific Dionex CR-ATC capillary trap column

Gradient: Potassium hydroxide, listed in figures.Flow Rate: 0.015 mL/minInj. Volume: 0.4 µLColumn Temp.: 30 °CDetection: A: Suppressed conductivity, Thermo

Scientific™ Dionex™ ACES™ 300 Anion Capillary Electrolytic Suppressor,recycle mode, Thermo Scientific Dionex Carbonate Removal Device (CRD 180).B: QD Charge Detection, Dionex QDCcell, 6 V, recycle mode.

Signal ∝ total charges

AX CX(+) (-)H2O

HYA+ Y-

AOH

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,µ

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3

Columns: Dionex IonPac AS11-HC-4µmcolumn set, 0.4 mm

Eluent Source: Dionex EGC-KOH capillary cartridge

Gradient: 1 mM KOH (5 min), 1–15 mM KOH (5–15 min),15–30 mM KOH (15–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Flow Rate: 0.015 mL/minInj. Volume: 0.4 µLColumn Temp.: 30 °CSystem Press.: 3600 psiDetection: A: Suppressed conductivity,

Dionex ACES 300 Anion Capillary Electrolytic Suppressor, recycle mode

B: QD Charge Detection, *normalized to chloride peak

Sample Prep.:Diluted 5-fold, filtered, 0.2 µm

Peaks: 1. Quinate 8. Malate-2. Lactate Succinate3. Acetate 9. Sulfate4. Glycolate 10. Oxalate5. Propionate 11. Phosphate6.Formate 12. Citrate7. Chloride 13. Isocitrate

Column: Dionex IonPac AS11-HC-4µm set, 0.4 mm

Eluent Source: Dionex EGC-KOH (Capillary) Gradient: 1 mM KOH (5 min),

1–15 mM KOH (5–15 min), 15–30 mM KOH (14–23 min), 30–60 mM KOH (23–31 min), 60 mM KOH (31–45 min)

Flow Rate: 0.015 mL/min

3 9

8

10

1213

14

15

16

17

18

1920

21

22

7

2

1

4

56

23

B) QD

11

1.3

-0.1

µA

Column: Dionex IonPac AG11-HC-4µm, Dionex IonPac AS11-HC-4µm, 0.4 mm

Gradient: 1 mM KOH for 8 min,1–15 mM KOH (8 to 18 min);15–30 mM KOH (18 to 28 min);30 to 60 mM KOH (28 to 38 min)

Eluent Source: Dionex EGC-KOH (Capillary)Flow Rate: 0.015 mL/min

FIGURE 2. Flow Diagram of the Dionex ICS-4000 HPIC System

FIGURE 1. Dionex ICS-4000 HPIC Dedicated Capillary System (FIGURE 1A), Interior view (FIGURE 1B), Thermo Scientific™ Dionex™ IC Cube™ with CD and QD Detectors (FIGURE 1C), QDC Charge Detector Cell (FIGURE 1D).

Figure 7 shows the higher proportional response of charge detection compared to conductivity detection for singly and multiply charged organic acids in a wine sample.3

FIGURE 7. Wine Sample, CD versus QD Response

1A.

1B.

1C.

1D.

Specific Conductance(µS/cm/mM)

HNO3 = 421CH3SO3H = 380HClO4 = 418NaNO3 = 121

Charge detection can be used to estimate concentration.1In charge detection, all the salts and acids with the same equivalency have similar responses (Figure 4) as compared with conductance where the salts have lower response.

FIGURE 4. Conductance versus Charge Detection.

Inj. Volume: 0.4µLTemperature: 30˚CSystem Press.: 3600 psiDetection: A) Suppressed conductivity,

Dionex ACES 300, AutoSuppression, recycle mode

B) Charge detection, 6 V, recycle mode

Peaks:1. Quinate2. Fluoride3. Lactate4. Acetate5. Propionate6. Formate7. Butyrate8. Pyruvate9. Galacturonate10. Chloride11. Tartrate12. Bromide13. Nitrate14. Glutarate15. Succinate16. Malate17. Carbonate18. Sulfate19. Fumrate20. Oxalate21. Phosphate22. Citrate 23. Isocitrate

* High pressure device+ Suppressor cartridge++ Dionex CRD 180 cartridge+++ Dionex IonPac ATC 500 trap

column

EGC*

EG Degas*

Dionex AS-AP Autosampler High-Pressure Dionex ICS-4000 HPIC System

Fresh 18 M Ω-cm Deionized WaterCR-

TC*

Pump*

waste

Columns

CD

IC CubeBack of IC Cube

4-port Valve

Dionex ACES+

Fresh 18 M Ω-cm Deionized Water

Syringe

Needle

Tray carousel

QD

++

Eluent flow path Regen flow path, not visible Regen flow path, visible

+++

Fluoride (Pka 3.17)

R² = 10

20

40

60

0 20 40 60 80 100 120

R² = 0.99990

5

10

15

20

0 20 40 60 80 100 120

Chloride

R² = 1

0

20

40

60

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-5

0

5

10

15

0 50 100 150

R² = 0.9998

-2

0

2

4

6

0 50 100 150

Chloride

R² = 0.9997

-202468

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)

FIGURE 5A. FIGURE 5B.

Figure 6 shows the QD chromatogram normalized at the chloride peak and overlaid on the CD chromatogram of a diluted guava juice sample.2 The chromatograms show a higher proportional charge with QD than CD for organic acids in diluted guava juice.

FIGURE 5. Compares CD (A) and QD (B) responses with concentration.

3

72 5,6

413

1

15

12

11

Minutes0 453010 4020

-5

µA*

30

µS

-10

100

AB

8

910

16

19

18

1417

20

9

8

10

121314

15

16

17

18

19 20

21

22

7

2 3

1 456

23

A) CD

11

Minutes0 453010 4020

µS

-0.2

2.8

FIGURE 6. Comparison of QD to CD Responses in Diluted Guava Juice

Figure 8 shows peaks in a diluted orange juice sample detected by QD but not CD (boxes).2 Peak 9 is an example of using CD/QD for peak purity analysis. Peak 9 was initially identified as nitrate but exhibits the QD response of a doubly charged organic acid.

µS 3

6

2

5 4

13

Minutes0 45

-203010 4020

90

1

7

8

9

10

11

12

µA*

-2

8

AB

Inj. Volume: 0.4 µLColumn Temp.:30 °CSystem Press.: 3600 psiDetection: A: Suppressed conductivity,




Peaks:1. Quinate2. Glycolate3. Lactate4. Acetate5. Formate6. Pyruvate7. Galacturonate8. Chloride9. Nitrate ?10. Glutarate11. Unknown12. Malate13. Maleate14. Unknown15. Sulfate16. Oxalate17. Phosphate18. Citrate 19. Isocitrate20. Unknown

TABLE 1. IC Conditions for Beverage Analysis.

3Thermo Scientific Poster Note • PN70725_e 06/13S






















MethodsSample Preparation

Commercial juice samples were diluted and filtered (0.2 µm) with a syringe filter.




.






AX CX(+) (-)H2O

HYA+ Y-

AOH

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,µ

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3













3 9

8

10

1213

14

15

16

17

18

1920

21

22

7

2

1

4

56

23

B) QD

11

1.3

-0.1

µA








1A.

1B.

1C.

1D.










column

EGC*

EG Degas*



TC*

Pump*

waste

Columns

CD


4-port Valve

Dionex ACES+


Syringe

Needle

Tray carousel

QD

++


+++

Fluoride (Pka 3.17)

R² = 10

20

40

60

0 20 40 60 80 100 120

R² = 0.99990

5

10

15

20

0 20 40 60 80 100 120

Chloride

R² = 1

0

20

40

60

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-5

0

5

10

15

0 50 100 150

R² = 0.9998

-2

0

2

4

6

0 50 100 150

Chloride

R² = 0.9997

-202468

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)




3

72 5,6

413

1

15

12

11

Minutes0 453010 4020

-5

µA*

30

µS

-10

100

AB

8

910

16

19

18

1417

20

9

8

10

121314

15

16

17

18

19 20

21

22

7

2 3

1 456

23

A) CD

11

Minutes0 453010 4020

µS

-0.2

2.8



µS 3

6

2

5 4

13

Minutes0 45

-203010 4020

90

1

7

8

9

10

11

12

µA*

-2

8

AB

































.






AX CX(+) (-)H2O

HYA+ Y-

AOH

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,µ

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3













3 9

8

10

1213

14

15

16

17

18

1920

21

22

7

2

1

4

56

23

B) QD

11

1.3

-0.1

µA








1A.

1B.

1C.

1D.










column

EGC*

EG Degas*



TC*

Pump*

waste

Columns

CD


4-port Valve

Dionex ACES+


Syringe

Needle

Tray carousel

QD

++


+++

Fluoride (Pka 3.17)

R² = 10

20

40

60

0 20 40 60 80 100 120

R² = 0.99990

5

10

15

20

0 20 40 60 80 100 120

Chloride

R² = 1

0

20

40

60

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-5

0

5

10

15

0 50 100 150

R² = 0.9998

-2

0

2

4

6

0 50 100 150

Chloride

R² = 0.9997

-202468

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)




3

72 5,6

413

1

15

12

11

Minutes0 453010 4020

-5

µA*

30

µS

-10

100

AB

8

910

16

19

18

1417

20

9

8

10

121314

15

16

17

18

19 20

21

22

7

2 3

1 456

23

A) CD

11

Minutes0 453010 4020

µS

-0.2

2.8



µS 3

6

2

5 4

13

Minutes0 45

-203010 4020

90

1

7

8

9

10

11

12

µA*

-2

8

AB







5Thermo Scientific Poster Note • PN70725_e 06/13S



























.






AX CX(+) (-)H2O

HYA+ Y-

AOH

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,µ

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3













3 9

8

10

1213

14

15

16

17

18

1920

21

22

7

2

1

4

56

23

B) QD

11

1.3

-0.1

µA








1A.

1B.

1C.

1D.










column

EGC*

EG Degas*



TC*

Pump*

waste

Columns

CD


4-port Valve

Dionex ACES+


Syringe

Needle

Tray carousel

QD

++


+++

Fluoride (Pka 3.17)

R² = 10

20

40

60

0 20 40 60 80 100 120

R² = 0.99990

5

10

15

20

0 20 40 60 80 100 120

Chloride

R² = 1

0

20

40

60

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-5

0

5

10

15

0 50 100 150

R² = 0.9998

-2

0

2

4

6

0 50 100 150

Chloride

R² = 0.9997

-202468

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)




3

72 5,6

413

1

15

12

11

Minutes0 453010 4020

-5

µA*

30

µS

-10

100

AB

8

910

16

19

18

1417

20

9

8

10

121314

15

16

17

18

19 20

21

22

7

2 3

1 456

23

A) CD

11

Minutes0 453010 4020

µS

-0.2

2.8



µS 3

6

2

5 4

13

Minutes0 45

-203010 4020

90

1

7

8

9

10

11

12

µA*

-2

8

AB

































.






AX CX(+) (-)H2O

HYA+ Y-

AOH

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,µ

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3













3 9

8

10

1213

14

15

16

17

18

1920

21

22

7

2

1

4

56

23

B) QD

11

1.3

-0.1

µA








1A.

1B.

1C.

1D.






Dionex ACES 300, AutoSuppression, recycle modeB) Charge detection, 6 V, recycle

mode



column

EGC*

EG Degas*



TC*

Pump*

waste

Columns

CD


4-port Valve

Dionex ACES+


Syringe

Needle

Tray carousel

QD

++


+++

Fluoride (Pka 3.17)

R² = 10

20

40

60

0 20 40 60 80 100 120

R² = 0.99990

5

10

15

20

0 20 40 60 80 100 120

Chloride

R² = 1

0

20

40

60

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-5

0

5

10

15

0 50 100 150

R² = 0.9998

-2

0

2

4

6

0 50 100 150

Chloride

R² = 0.9997

-202468

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)




3

72 5,6

413

1

15

12

11

Minutes0 453010 4020

-5

µA*

30

µS

-10

100

AB

8

910

16

19

18

1417

20

9

8

10

121314

15

16

17

18

19 20

21

22

7

2 3

1 456

23

A) CD

11

Minutes0 453010 4020

µS

-0.2

2.8



µS 3

6

2

5 4

13

Minutes0 45

-203010 4020

90

1

7

8

9

10

11

12

µA*

-2

8

AB







Thermo Fisher Scientific, Sunnyvale, CA USA is ISO 9001:2008 Certified.

PN70725_E 06/13S

www.thermoscientific.com©2013 Thermo Fisher Scientific Inc. All rights reserved. ISO is a trademark of the International Standards Organization. All other trademarks are the property of Thermo Fisher Scientific Inc. and its subsidiaries. This information is presented as an example of the capabilities of Thermo Fisher Scientific Inc. products. It is not intended to encourage use of these products in any manners that might infringe the intellectual property rights of others. Specifications, terms and pricing are subject to change. Not all products are available in all countries. Please consult your local sales representative for details.

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.






AX CX(+) (-)H2O

HYA+ Y-

AOH

0 20 40 60Time, min

28

28.4

28.8

29.2

29.6

30

Curre

nt,µ

A

HClO4CH3SO3HHNO3

KClNaCl

NaNO3













3 9

8

10

1213

14

15

16

17

18

1920

21

22

7

2

1

4

56

23

B) QD

11

1.3

-0.1

µA








1A.

1B.

1C.

1D.










column

EGC*

EG Degas*



TC*

Pump*

waste

Columns

CD


4-port Valve

Dionex ACES+


Syringe

Needle

Tray carousel

QD

++


+++

Fluoride (Pka 3.17)

R² = 10

20

40

60

0 20 40 60 80 100 120

R² = 0.99990

5

10

15

20

0 20 40 60 80 100 120

Chloride

R² = 1

0

20

40

60

0 20 40 60 80 100 120

Formate (Pka 3.75)

R² = 0.9999

-5

0

5

10

15

0 50 100 150

R² = 0.9998

-2

0

2

4

6

0 50 100 150

Chloride

R² = 0.9997

-202468

0 50 100 150

Fluoride (Pka 3.17)

Formate (Pka 3.75)




3

72 5,6

413

1

15

12

11

Minutes0 453010 4020

-5

µA*

30

µS

-10

100

AB

8

910

16

19

18

1417

20

9

8

10

121314

15

16

17

18

19 20

21

22

7

2 3

1 456

23

A) CD

11

Minutes0 453010 4020

µS

-0.2

2.8



µS 3

6

2

5 4

13

Minutes0 45

-203010 4020

90

1

7

8

9

10

11

12

µA*

-2

8

AB







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