Maximizing Efficiency in Analysis through New GC-MS Approaches Richard Fussell Vertical Marketing Manager, Food and Beverage, Thermo Fisher Scientific, Hemel Hempstead, UK Dominic Roberts Senior Applications Scientist, GC-MS, Thermo Fisher Scientific, Runcorn, UK PO71686-EN 0615S
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Chromatography: Pesticide Residue Analysis Webinar Series: Part 3 of 4: Maximizing Analysis Efficiency through GC-MS Approaches
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Maximizing Efficiency in Analysis through New GC-MS Approaches
Richard Fussell
Vertical Marketing Manager, Food and Beverage, Thermo Fisher Scientific, Hemel Hempstead, UK Dominic Roberts Senior Applications Scientist, GC-MS, Thermo Fisher Scientific, Runcorn, UK PO71686-EN 0615S
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Overview • The analytical challenge
• User requirements for GC-MS/MS analysis of pesticides • Critical aspects of the method & improving efficiency
Longer column lifetime Less frequent inlet maintenance
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Selectivity: Selected Ion Monitoring (SIM) and SRM
DDE-p,p’, 0.05 mg/kg in green tea, 1.0 uL splitless injection
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Selectivity: SIM and SRM
DDE-p,p’, 0.001 mg/kg in green tea, 1.0 uL splitless injection
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Proprietary & Confidential
Key Factors in the GC-MS/MS Method
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Hot split/splitless
Programmed Temperature
PTV
Typical GC Injector Choices for pesticides
• Liquid introduction by syringe
“GC Injection is the Achilles Heel in GC”
Bertsch 1983, Univ. Alabama
• Most commonly used technique • Split/Splitless injection (SSL) • Programmed temperature (PTV)
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GC Inlets • Splitless
• maximum sensitivity • excellent repeatability for low volumes • simple, probably most wide used
• Split
• reproducible • less discrimination (short residence time) • Shoot and Dilute
• Programmed Temperature Vaporising (PTV) injector • versatile and excellent performance if optimised • reduced discrimination • many liner types (baffled, dimpled, packed, etc) • packed liners (possible discrimination) • large volume injection (solvent removal/exchange in liner)
• Cool on-column (not widely used)
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GC Liner Selection for Pesticides
• In pesticide analyisis QuEChERS extractions are typical and result in extractions in acetonitrile.
• Many labs use acetonitrile as GC injection solvent • Requires careful method optimisation
• Considerations in liner selection for acetonitrile injections are: • Internal diameter • Type of injection • Packing of liner • Other liner features ie baffles....
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GC liners – Type of Injection
• Split • Typically open ended at the bottom • Enables split flow to pass across the bottom of the liner removing a portion of the
sample, allowing a split injection to be performed
• Splitless
• Typically tapered at the bottom with the column inserted into the taper • Funnels sample onto the column and minimizes sample contact with reactive metal
components
• PTV • Generally used with very active compounds such as pesticides • Good option for acetonitrile injection solvents • Thermally liable compounds protected
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PTV Injector: Key Points
• Minimal thermal mass for fast cooling and heating
• Injection volumes from nano liter up to largevolume
• Cold injection technique
• Clean step possibility for keeping the liner inert
• Multiple injection modes
OVEN column
Liner
Cooling by fan Heater element
Inlet Carrier Septum Purge
Split line
Slide courtesy of Thermo Fisher Scientific
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System Contamination with Heavy Matrices
9.03 min (start of run)
1.0 µg/ml dimethoate in crude extracts of lettuce - 3 µl splitless
Chromatograms for EtAc solvent after injection (n=10) of QuEChERS extracts with back-flush and without back-flush
Slide courtesy of Fera, UK
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Guard columns
• Analytical columns with a length of 5-10 m of deactivated fused silica. They can be purchased already integrated or joined by a union.
• Provides the benefit of protecting the analytical column from
contamination of non-volatile residues. Very important when working with dirty sample extracts eg. QuEChERS.
• Can also act as a retention gap to improve analyte focussing. • Maintain retention time of analytes and SRM segments in the method. • Can be a source of leaks if using a connection. • Added maintenance
Thermo Scientific TSQ 8000 Evo GC-MS/MS
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Increasing Laboratory Productivity
• Decrease analysis time by shortening the GC run times. • More samples in less time.
• Increase the number of pesticides in a run. • More SRMs to accommodate within an analytical run.
• Improve selectivity for various matrices. • Increased number of SRMs per compound.
• See beyond the targets. • Full Scan and SRM data acquisition in the same experiment.
Expect More Performance
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Fast GC-MS Pesticide Residue Analysis
Challenges:
• Complexity of elution when using fast GC
• Large number of compounds (SRMs) in short time
• Many SRM transitions can result in sensitivity loss
Solution:
• High speed analyzer • Fast collision cell • Short SRM dwell times with very
• Rapid, innovative collision cell technology • Increased method capacity • More compounds • More SRM transitions • Up to 4x more transitions whilst maintaining method sensitivity low analyte concentrations
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Increasing Laboratory Productivity
• Decrease the analysis time by shortening the GC run times. • More samples in less time. • More SRM Increase the number of pesticides in a run. • s to accommodate within an analytical run.
• Improved selectivity for various matrices • Increase the number of SRMs per compound.
• Seeing beyond the targets • Full Scan and SRM data acquisition in the same experiment.
Full Scan 144 pesticides in baby food @ 0.2 mg/kg TG-5 SILMS, 20m x 0.18 mm x 0.18 µm GC run time: <11 min
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Pesticide MRM Database
The problem:
• Growing list of target compounds require continuous adjustment to an existing SRM database.
• Some SRM transitions are not suitable for all matrices. Addition of new SRM transitions can be time consuming.
The solution:
• Automated SRM development with AutoSRM.
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AutoSRM: Fast, Simple Route to Optimized SRM
1) Precursor ion selection
2) Product ion selection
3) Collision energy optimization
AutoSRM automates the development of SRM methodology
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Highlights of AutoSRM
• Automates the following: • Creation of full scan, product ion scan, and SRM methods • Creation of sample sequences • Creation of data layouts for analyzing results • Selection of precursor, product, and collision energies
End result showing optimized transition
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Timed-SRM: Using Dwell Times Efficiently
Classical segmented SRM
TSQ 8000 EVO timed SRM
Classical segmented SRM:
• Complex to set up • Wasted dwell time • Reduced sensitivity • Reduced tolerance to RT shifts
TSQ 8000 Evo timed-SRM:
• Automated set-up • Full optimized dwell time • Optimal sensitivity • Increased resistance to RT shifts
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Increase Laboratory Productivity
• Decrease the analysis time by shortening the GC run times. • More samples in less time.
• Increase the number of pesticides in a run. • More SRMs to accommodate within an analytical run.
• Improved selectivity for various matrices • Increase the number of SRMs per compound.
• Seeing beyond the targets • Full Scan and SRM data acquisition in the same experiment.
GC High Resolution Mass Spectrometry for Pesticide Analysis
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Q Exactive GC for Pesticide Analysis
• Launched at ASMS June 2015. • Screen (qualitative and quantitative) samples for pesticides within a single
analysis, fast and at a competitive cost.
• To increase the scope of the analysis, by using high resolution full scan mass spectrometry.
• Untargeted analysis where a generic full scan acquisition is run, followed by targeted data processing of a list of compounds.
• Retrospective data analysis is possible to identify new compounds that were not screened for at the time of acquisition.
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The Power of Accurate Mass
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An Example Study
• To evaluate the performance of Thermo Scientific Q Exactive GC hybrid quadrupole-Orbitrap mass spectrometer for the reliable screening of GC amenable pesticides.
• To screen for a wide range of pesticides in different sample matrices with the highest level of confidence possible.
• To determine if a pesticide is present in a sample above the MRL which is typically 10 ng/g (ppb).
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Experimental • Sample introduction was performed using a Thermo Scientific™ TriPlus™ RSH
autosampler, and chromatographic separation was obtained with a Thermo Scientific™ TRACE™ 1310 GC. Thermo Scientific™ TraceGOLD TG-5SilMS 15 m x 0.25 mm I.D. x 0.25 µm film capillary column.
• Q Exactive GC hybrid quadrupole-orbitrap mass spectrometer was used. The system was
operated in EI using full scan and 15k, 30k, 60K and 120k resolution (FWHM, m/z 200). Data was acquired with a minimum of 10 points/peak.
• Data was acquired and processed using the TraceFinder version 3.3 software.
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RESULTS
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Screening Criteria Used for Positive Identification
Iden%fica%on Point Tolerance Primary ID Confirmatory ID
Effect of Resolving Power on Mass Accuracy Chlorpropham in Leek (10 ng/g)
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Scan Speed and Accurate Mass Across Peaks 60K
• XIC of diazinon(m/z 179.11789 ±5 ppm mass window) in wheat at 10 ng/g showing ~11 scans/peak (peak width 1.8 sec).
Average = 0.33 ppm RMS
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Maintaining Sensitivity with Resolution
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Linearity
• XIC (quan and confirm ions) and calibration curve for Fenpropimorph in leek.
• Triplicate injections of the calibration series was performed with good linearity across (0.5 – 50 ng/g).
• No internal standard correction.
R2 = 0.9999
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Conclusions
• Careful method optimisation focussing on the injection parameters.
• Routine pesticides analysis with the EVO offers sensitivity, high analysis speed and easy database management at low cost
• Using the available dwell time wisely: • Timed-SRM ensures minimal loss of time spent to acquire data.
• Q Exactive GC system improves efficiency by increasing the scope of the analysis:
• Full scan non-targeted acquisition. • Provides the required sensitivity and selectivity in complex matrices for routine
pesticide screening and quantification. • Enables the detection and identification of unknown compounds.
Efficient and robust pesticide analysis can be achieved by:
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Thermo Scientific Food and Environmental Communities: Resources • View application notes, on-demand webinars, product information, and
many more resources on our Pesticides and Food Communities Libraries: www.thermoscientific.com/pesticides www.thermoscientific.com/foodandbeverage
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Thank You for Listening
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