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Innovations in FTIR Technology for the Rapid Analysis of Liquid Petrochemical Samples
Lou Tisinger
FTIR/FTIR Imaging and Microscopy
21 June 2012 1
POM
QA/QC, Geoscience,
Art Conservation,
Materials & Surfaces
Analyzer
Fuel BioDiesel QA/QC
Routine
QA/QC Pharma & Chemical, Academia
Mid
Chemicals, Petrochem, Food/Ag,
Forensics, Bio Research
High
Materials & Polymers,
Bio Research, Forensics
FTIR Product Line
Agilent 4500/5500 DialPath/Tumbler makes measurement easy
Agilent 4500/5500 DialPath/Tumbler
• Easy to clean liquid cell • Reproducible path length
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DialPath Sampling Technology
•Agilent-exclusive DialPath/Tumbler technology features an “open cell” transmission design for qualitative and quantitative FTIR analyses of
liquids. •As easy for liquid measurement as using ATR, and with the added
benefit of variable and extended pathlength
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Three simple steps to measuring liquids!
Pathlength (μm) Typical Conc. Range 30 Neat - 0.1% 50 50% - 500 ppm 100 20% - 100 ppm 200 10 % - 50 ppm
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Dialpath Geometry 3 µ L Fill Volume
250 µ L Fill Volume
µ L Fill Volume
250 µ L Fill Volume
The combination of class-leading performance and rapid scanning capability means that most liquid samples can be measured in < 30 secs. Volatile liquids require > 120 secs. to show any appreciable change in concentration, once placed in the DialPath cell that is in the closed position.
Advantages of DialPath Technology for analysis of liquids • Non-viscous and/or volatile liquids
can easily fill the DialPath, even when in the “close” position, by simple “capillary action” as touching the liquid between the windows, will draw the liquid in.
• Viscous samples (oils, syrups, etc) can easily fill DialPath in open position
• Effective for volatile solutes and/or solvents since detectable evaporation takes much longer than typical measurement times.
• Post analysis cleaning is a simple process; both windows are exposed and need only be wiped off
3 µ L Fill Volume
250 µ L Fill Volume
µ L Fill Volume
250 µ L Fill Volume
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• Standards of benzene in hexane were prepared
• Evaluation samples of 0.5% benzene in hexane were prepared and measured. 18 sec scan time was employed for both calibration and evaluation samples
• Reproducibility of 0.5% sample was measured with increasing time delays of 0 to 60 sec.
• Red line is mean benzene concentration measured at zero delay time; purple lines are +/- 2% error bars
Benzene in Hexane Method Prediction Variations of a Nominally 0.5vol% Standard, Testing the Possible Effects of Solvent and Solute Evaporation, Using
the TumblIR Transmission Cell
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0 0 45 45 45 60 60 60Time Delay (seconds) After Adding Sample to TumblIR Cell
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Benzene Vol%
Concentration of a volatile benzene analyte measured in volatile hexane solvent shows no significant change up 60 secs after analysis initiates.
Solvent evaporation with DialPath – Benzene in hexane
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Summary
• Dialpath/Tumbler provides for liquid transmission as easy as ATR
• Dialpath provides for a variable pathlength, from 30 to 250 microns to greater range of concentrations measurements
• Suitable for viscous and even highly volatile liquids, with little or no detectable evaporation effects up to 1 minute measurement time
Environment – Oil in Water by Extraction
Oil in water a key environmental measurement
• FTIR measurement by Extraction
• Historically extracted by Freon 113 (ASTM D3921) • Currently extracted by S 316 (ASTM 7066-04) • Also extracted by cyclohexane in ASTM D7678 • Oil measured directly in extracted fluid using Transmission
Agilent 4500/5500 DialPath makes measurement easy
• Easy to clean liquid cell • Reproducible path length • Easy to use software
Red or Green results will tell the user if there is critical warning and recommend the next steps
Environment – Oil in Water by Cyclohexane Extraction (ASTM D7678)
Previous Freon FTIR extraction method is being phased out
• Freon and other halogenated solvents have been banned by the Montreal protocol due to their ozone depleting activity
Cyclohexane is a CFC free non-ozone depleting solvent
Agilent’s FTIR version of the ASTM D7678 features a limit of quantification (LOQ) of .75mg/L (0.75ppm) oil in water
Standard procedures for liquid-liquid solvent extraction remain unchanged from previous ASTM methods.
These ASTM D7678 based FTIR results will correlate to other methods
• ASTM D3921, D7066, ISO 9377-2, EPA 413.2, and 418.1 methods
Simple 5 step process 1. Add Cyclohexane Add 20mL of cyclohexane to 900mL of process water and vigorously shake for 2minutes.
2. Remove Top Layer Allow layers to separate, and remove the top layer for analysis
3. Add Cleaning Agents Add 2g drying agent (sodium sulfate) and 2g Florisil™ to the cyclohexane extract, shake
vigorously, and allow to settle for 2minutes.
4. Filter Cyclohexane Extract Filter the “cleaned” cyclohexane with a 0.45um nylon syringe filter (17mm).
5. Measure FTIR Spectrum Add the cyclohexane to the Dialpath™ or TumblIR™ cell and initiate the FTIR scanning.
The result will be displayed after 30seconds of scanning.
Environment – Oil in Water by Cyclohexane Extraction (ASTM D7678) Simplified Procedure
The overlaid FT-IR spectra of crude oil (Blue) and mineral oil (Red). The zoomed region indicates the local baseline (dashed line) used for the 1378cm-1 peak area measurement by FTIR.
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Mineral oil (abs area) = 2.661
The FTIR spectrum of cyclohexane, Dialpath attachment. The zoom box indicates the overlaid spectral region of the hydrocarbons using the methyl absorbance at 1378cm-1.
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Hydrocarbons, Methyl Bend Absorbance
The mineral oil in cyclohexane calibration plot of actual (x-axis) vs. predicted (y-axis) values. The values displayed are the final concentrations of oil in water based on the ASTM D7678 parameters (900mL water, 20mL cyclohexane).
Oil Calibration SetStandard Name Oil (mg/L)OIW Soln A 0.00OIW Soln B 0.05OIW Soln C 0.15OIW Soln D 0.26OIW Soln E 0.84OIW Soln F 1.70OIW Soln G 2.54OIW Soln H 4.20OIW Soln I 8.30OIW Soln J 16.54OIW Soln K 24.90OIW Soln L 32.55
OIW Validation Results – Samples are 9.3mg/L (solution A) and 1.4mg/L (solution B) mineral oil respectively
Solution A Solution B9.70 1.349.43 1.549.12 1.449.60 1.46
Mean Value 9.46 1.45Std. Deviation 0.25 0.08Relative Std. Dev. (%) 2.69 5.69% Recovery 101.7 103.2
TPH
The samples are measured in quadruplicate with the Dialpath™ accessory.
The automatically obtained data results from the MicroLab software for the Agilent Cary 630, 4500series, and 5500series FTIR spectrometers.
Using Mobile FTIR to Measure Gasoline in Diesel
The intensity of an infrared absorbance band is proportional to the concentration of that component in a mixture, as stated in Beer’s Law. This relationship allows the Agilent 5500t and 4500t FTIR spectrometers to accurately measure gasoline in diesel fuels.
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4500t FTIR Series
5500t FTIR Series
Chemical Differences Between Gasoline and Diesel
Figure 1. The IR spectral overlay of gasoline (Blue) and diesel fuel (Red) using the Agilent 5500t FTIR spectrometer, 100 μm pathlength
The chemical differences between gasoline and diesel can be seen in the infrared spectrum of each. Below is a comparison between the infrared spectra of gasoline and diesel highlighting the ethanol and aromatics in gasoline. Neither ethanol or light aromatics present in gasoline are observed in the diesel fuel spectrum; in fact, the spectrum of diesel fuel is similar to mineral oil.
The Sensitivity of Mobile FTIR
The sensitivity of the 5500t FTIR allows gasoline to be measured down to 0.025 % in diesel. To demonstrate this, several concentrations of gasoline (87 octane) are carefully prepared in ultra low sulfur diesel (US, Danbury CT). The samples were prepared with 0 %, 0.0269 %, 0.2669 %, and 1.0586 % gasoline in diesel. The FTIR spectra were measured on the 5500t spectrometer and the gasoline absorbance results are plotted against their concentrations. This gasoline absorbance plot indicates a very good linear correlation with concentration.
Figure 2. The IR absorbance vs. concentration plot for gasoline in diesel, Agilent 5500t FTIR 100 um pathlength
Gasoline absorbance results are plotted against their concentrations
3 Minute Mobile FTIR Analysis
Linear correlation is common in spectroscopy and can be easily added to 5500 or 4500 FTIR methods. Multiple components can be reported from a single 3 minute analysis, such as gasoline in diesel, biodiesel in diesel, oxidation, and water.
The instrument can be operated from a laptop (5500t) or the Agilent 4500t FTIR which is a fully field portable version with an onboard battery and operated from a hand held computer (PDA). The instrument software is simple to use with little to no sample preparation.
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Red or Green results will tell the user if there is critical warning and recommend the next steps
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Advancement in Mobile Solutions – Taking On-Site Measurements is Now Easier Than Ever
21 June 2012 23
Value of Moving Measurements From the Lab to the Field Fast answers Define sampling strategy based on current
results Triage - Send more relevant samples back to
lab. Decide which areas need more investigation.
Non-destructive analysis of large objects Too big for lab Too expensive to disassemble
Screen incoming materials before they enter the production process
On-site adulteration or contamination determination
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Instrument Requirements Needed for Field and Routine Use Effective performance Achieve required measurement limits “Spectroscopic performance still matters”
Form Factor – Compact, rugged, portable, versatile System needs to go where the sample is Frequent travel subjects it to ↑ shock and
vibration Correct sampling interfaces Little or no sample prep Multiple uses and matrices
Ease of use and provide answers Easy to understand, meaningful results
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What approach does Agilent Technologies take when designing systems for field use?
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Develop high performance optical engine
Integrate engine into appropriate form factors
4100 Exoscan / 4200 Flexscan – handheld Cary 630 – routine lab
Lab systems benefit -> compact size and robustness
Field systems benefit -> spectroscopic performance
Easy method transfer from development lab to field
Cary 630 routine benchtop 4100 handheld
4100 in lab configuration
4200 FlexScan
Dual Nature of the Agilent 4100 ExoScan
Method development for field applications is often accomplished in the lab
Exoscan was designed to specifically meet this need Docking Station Convert handheld system into bench-top system PC connection Sample stages
Interchangeable sample interfaces
Increased flexibility
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Instrument Evolution
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Laboratory (1970’s)
Spectroscopy Measurements Continue to Move Directly to the Sample
Current (Today)
Field FTIR Form Factor
4 lbs optical head Optical Enclosure wire connected to Electronics PDA Controlled Dedicated sample interfaces
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4100 ExoScan FTIR 4200 FlexScan FTIR
7 lbs 7” x 4.7” x 9” inches Single Enclosure (optics & electronics) PDA Controlled Interchangeable sample interfaces
Field Sample Interfaces ATR
Solids or liquids Easy sample identification Diamond and Germanium available
External Reflectance (45⁰)
Metal and composite surfaces Specular reflectance or reflection absorption Surface oxidation, coating thickness and chemistry
Grazing Angle (~82⁰)
Smooth metal surfaces Enhanced absorption Trace contaminant identification
Diffuse Reflectance
Normal incidence Large collection angle Low reflective samples
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Identifying applications that can be migrated to the field Does the measurement involves chemical differences? Change in concentration, thickness, oxidation, chemical damage, UV
degradation, presence or absence of chemical, etc?
Is the measurement made by FTIR in the lab?
Do you have access to the sample? Not behind glass or plastic
Is there an advantage to field measurement? Speed or non-destructive
Actionable limit ATR ~ 1 % Diffuse Reflectance ~ 0.01 – 0.1% External Reflectance ~ 0.05 mils or ~ 2 μg/cm2
Grazing Angle ~ 0.2 μg/cm2
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Considerations for Handheld Measurements
Sample Interface Substrate Required limit Ability to measure handheld
Diffuse or external reflectance easier than ATR Diffuse most forgiving WRT focus
Measurement Time ↑ Time = ↓ Noise…. however How long can the user keep the system steady
Especially true for ATR Sometimes shorter = better measurement.
Meaningful Results Must be useable No interpretation required
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Considerations for Identifying “Good” Data Reflectance techniques can produce negative or totally absorbing bands Often due to strongly absorbing samples No sample preparation
Useful data can often be found outside these regions Example: Sulfate concentration in soil High percentage of sand = strongly absorbing Si-O bands Overlap sulfate absorbance Overtone of sulfate at 2200 cm-1 correlates well with sulfate concentration
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ATR’s ease of use SHOULD make it ideal for hand held use No sample preparation High signal to noise Consistent path length High acceptance in lab
BUT one feature makes hand held use difficult -> CONTACT
Crystal/sample contact is the key - > Flatness not pressure In Lab, press brings crystal and sample in line In Field, contact is made with hand movement – hard to keep steady
Crystal Geometry is the ANSWER
Spherical surface makes good contact at many angles Strong absorbance is observed even with a light touch
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Sample Interface Considerations - ATR
How are methods developed and what types of methods are useful?
Useable results require intelligent output Methods developed for specific applications Most methods are universal Only developed once Usable on all instruments of the same type
Qualitative Methods Standard library search techniques Smaller libraries = focused results
Quantitative methods Meaningful units to the end user Threshold limited and color coded Often Multivariate methods
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Implementing methods into end user software
Software guides the user through the
selected method and gives users
instructions to prevent mistakes.
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Displaying Meaningful Results
Library results are shown with the hit list
Quant results can be programmed for action levels with color codes
(red, green, yellow)
Exoscan can identify all 10 groups of seals Fluorosilicone, Silicone, Viton, EPR/EPDM, Neoprene, Butyl, Kalrez, NBR, Polyurethane, Natural Rubber
Easy Identification by spectral search Similarity = correlation Highest correlation = correct ID
Demonstration 15 samples Exoscan correctly identified all samples Only one sample had a close second match
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Hand Held FTIR Material Identification O-ring and Seal Identification
Hand Held FTIR Coating Analysis
Sensitivity of FTIR is ideal for thin coatings - Primers, adhesives, protective coats
Ideal thickness required - Cost and performance
Many types of surfaces
Two examples: - Epoxy primer - Ultra thin anodization
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Epoxy paint primer on aluminum
Ideal thickness ~ 0.2 mils
Range from 0.5 to 5.0 mils
Linear correlation to epoxy band at 1610 cm-1
Upper Limit of Quant = 0.6 mils R2 = 0.99
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Epoxy Primer Thickness External Reflectance
Ultra Thin Anodization Coating Thickness Grazing Angle
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Metal Oxide Peak 1Metal OxidePeak 21 µm
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Anodization on aluminum Thickness crucial for further coating Exoscan – Grazing angle ~10 second measurement time LOD ~ 25 nm thickness Action Level = 0.5 μm
Conclusions
Instruments are moving out of the lab to give users cost and measurement advantages
As they move out, design philosophies must accommodate new requirements
Size, weight, durability and usability Given the right design, instruments can perform as well as many lab systems
The realities of handheld measurement require method developers to consider the entire measurement process.
4100 ExoScan development supports both field and method development Well developed methods can provide easy data acquisition and actionable
answers even on difficult samples.
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