gas chromatography pesticide analysisA recently released article on the title of this post is the genesis of this blog post. How this came about is as follows. Soon after the article, Application of the precolumn back-flush technology in pesticide residue analysis: A practical view, (link to abstract) was released, our APAC GC/MS Technical Director,Hans-Joachim Hubschmann, Ph.D., sent an email saying that this was an excellent read and recommended it. Immediately, I asked if he would provide his thoughts on the topic and he did!

And, here is what Dr. Hubschmann wrote in its entirety with minor editing.

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Concerned about Dirty Matrix Samples in GC and GC-MS?

A Proven Solution for Sample Throughput, Productivity and Reduced Maintenance

Use the proven pre-column backflush technology offered by Thermo Fisher Scientific for the complete range of gas chromatography (GC) and GC-MS systems. The concurrent back flushing and cleaning of a pre-column and injector during the analysis run is a unique solution only available with Thermo Fisher Scientific GC and GC-MS systems. More samples can be measured with significantly better analytical performance, shorter analysis times can be used, and there is less routine maintenance required for extended system uptime, all together adding to increased productivity for the routine lab.

The concurrent backflush solution was especially implemented into the newly launched Thermo Scientific Trace 1300 GC system for the new requirements of multi-class multi-residue methods as they are typically used for instance in pesticides analysis using the popular QuEChERS extraction method (link to Wikipedia page) according to the official methods AOAC 2007.01 (downloadable PDF) and CEN 15662 (link to CEN page from where you can download the PDF).

The concurrent pre-column backflush is not new. The solution was first presented by Thermo Fisher Scientific in 2000 at the traditional International Chromatography Conference in Riva del Garda, Italy. The unique benefits stated in this publication are more than actual still today: “The device allows to backflush the heavy components of the sample when they are not of interest, allowing to shorten analysis time and better select the column for the separation of the volatile components. Additionally the device allows … to isolate the injector, while maintaining the carrier flow through the column, when changing the liner or the septum” [1].

A very recent publication by Fanny Hildmann from the Department of Pesticides of the Saxon State Laboratory of Health and Veterinary Affairs in Dresden, Germany, demonstrates the unique benefits of the concurrent back flushing in GC-MS/MS analyses [2]. Difficult samples had been prepared by using the QuEChERS method including fruit, vegetables, samples of animal origin and lemon oil.

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The RSDs of the peak area were determined to be less than 10% for 61% of the of 99 spiked pesticide analytes using pre-column back-flushing. Without back-flushing, no pesticide resulted in these low RSDs. With regard to maintenance intervals the pre-column had to be replaced first after 80–400 injections. Especially the injections of edible oil extracts or samples of animal origin with a high fat content resulted in a strongly contaminated pre-column, but kept the analytical column clean for an increased number of injections. No clipping of the analytical column was necessary keeping all retention times in place. The lifetime of the analytical column was increased to the double number of analysis using the backflush module.

The full article is available for detailed study of the experimental conditions used with the DOI 10.1002/jssc.201300007.

References

[1] Munari, F., Magni, P., Facchetti, R., Improvements in PTV Large Volume Injection and MS Detection Using a Reverse Flow Injection Device, Riva del Garda ISCC Conference, 2000.

[2] Hildmann, F., Kempe, G., Speer, K., Application of the pre-column back-flush technology in pesticide residue analysis: A practical view, J. Sep. Sci. 36 (2013), 2128–2135.

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Don’t forget to check other chromatography applications for pesticide analysis on this blog.

And, as always, do let us know if you have any questions using the the Comments box below; our experts look forward to hearing from you.