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As discussed in our recent blog post on pesticide analysis, many jurisdictions have strict legislation and testing requirements for the creation and use of new pesticides and their metabolites, and typically require both identification and quantitation of select pesticides in agricultural products. For those working in the pesticide residue analysis space, effectively measuring pesticides in a short amount of time is a key concern.

Results from a new study by JEOL researchers show that the markedly-reduced elution time offered by an LPGC column and the ability of the short collision cell in a JMS-TQ4000GC GC-MS/MS to distinguish a large number of coeluting peaks make these two technologies a natural pairing, particularly for pesticide analysis. Read on to learn how leveraging these two key technologies can save you time in the lab.

Low-Pressure Gas Chromatography

Low-pressure gas chromatography (LPGC) is a technique that uses a short, wide-bore analytical GC column and the vacuum inlet of a MS to significantly decrease elution time with very little sacrifice to separation efficiency.

To summarize the theory of LPGC, the wide-bore column and MS vacuum reduce the pressure within the column, which decreases carrier gas viscosity and increases the optimum linear velocity.  The result is decreased elution time while maintaining a similar theoretical plate height (separation efficiency).  The addition of a restrictor column allows the GC inlet to maintain head pressure and the software to calculate gas flow conditions correctly.  

The LPGC column kit used in this study is available from Restek and comes with the analytical column and restrictor column pre-connected for easy installation, and an integrated transfer line that reduces background and stabilization time.

Short Collision Cell Technology

Because pesticide compounds are expected to elute faster and closer together when using an LPGC column, MS/MS will be even more critical to differentiate individual pesticides.  For triple-quadrupole MS/MS, dwell time and maximum SRM switching speeds are important for either maximizing sensitivity or measuring more compounds simultaneously.  

JEOL’s JMS-TQ4000GC contains a short collision cell that allows a minimum dwell time of 1 ms and a maximum switching speed of 1,000 SRMs/s.  The short collision cell design uses two patented technologies to increase the speed and sensitivity of the analysis. 

 

Mass spectrometry data showing increased speed of pesticide collection using LPGC Column

Methods

In this study, Triple-quadrupole tandem mass spectrometry (standard EI+ at 70 eV) was used to measure pesticides eluting from a low-pressure gas chromatograph (LPGC) capillary column.  Three transitions for each of 244 pesticide compounds were measured within 11 minutes, and the data were checked to confirm the method’s reproducibility and ability to distinguish all three transitions for each pesticide.

Researchers found that all three transitions for all 244 pesticides were detected in the standard mixture at 1X concentration within the 11-minute analysis time.  Relative standard deviation (RSD) of peak areas was less than 15% for 242 pesticides, and I/Q RSDs were less than 10% for 242 compounds.  Retention time RSD over 15 replicates was less than 0.1%.

JEOL’s Triple-Quad Mass Spectrometer

JEOL has over 70 years of expertise in crafting advanced scientific instrumentation, and our JMS-TQ4000GC triple-quad mass spectrometer has been designed with pesticide analysis in mind. To learn more about using low-pressure gas chromatography and short collision cell technology to speed your workflow, check out this on-demand webinar.



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