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Contamination Eliminated in GC Food Analysis
August 6, 2010
Thermo Fisher Scientific Inc. developed a new method to effectively eliminate invisible high boiling matrices in the analysis of pesticides in food.
Incorporating a programmable temperature vaporizing injector, the Thermo Scientific TRACE GC Ultra GC/MS analyzer produces analysis of pesticides in low fat food products, enhancing the productivity and efficiency of gas chromatography and gas chromatography mass spectrometry systems for analyzing pesticides in food, while eradicating high boiling matrix.
The new method is detailed in an application note, entitled “Eliminate Invisible High Boiling Matrix in GC and GC/MS by Using PTV Backflush Injection Technique for Increased Productivity and Reliability,” which is available to download at www.thermoscientific.com/ptv.
Pesticide extraction in low-fat food products, such as fruits and vegetables, normally results in high concentrations of lipid components as a matrix of high boiling compounds in the extracts.
Once injected into a GC or GC/MS analyzer, high boiling substances accumulate on the analytical column of the system, contaminating it and causing an increasingly high background level.
As high boiling compounds cannot be seen, there is no possibility of visual quality control. Bake-out procedures have been traditionally used, but these methods increase time between samples, are inefficient and reduce the column lifetime. An optimum solution would be the separation of the analytes from all high-boiling matrix material directly after injection.
The new application demonstrates that a PTV injector with a pre-column and a carrier gas backflush capability offers a powerful method for separating analytes from high-boiling compounds.
Following sample extraction using the QuEChERS technique, a PTV injector was used to inject the extract into the TRACE GC Ultra GC/MS analyzer.
Pesticides traveled quickly into the system’s analytical column, whereas high boilers were kept in the pre-column that was swept backward concurrently during the analytical run.
As a result, the analytes transferred to the column and eluting to the MS source were free from high molecular weight compounds. Experimental results demonstrated that the PTV-GC/MS system can be used for both regular and large volume injections with productivity advantages.
Source: Thermo Fisher Scientific
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