Aug 3 2010 --- Thermo Fisher Scientific Inc. has announced a new method to effectively eliminate invisible high boiling matrices in the analysis of pesticides in food. Incorporating a programmable temperature vaporizing (PTV) injector, the Thermo Scientific TRACE GC Ultra GC/MS analyzer achieves sensitive, fast and reliable analysis of pesticides in low fat food products, significantly enhancing the productivity and efficiency of gas chromatography (GC) and gas chromatography mass spectrometry (GC/MS) 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."

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 from Thermo Fisher 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 Thermo Scientific TRACE GC Ultra GC/MS analyzer.

Pesticides travelled quickly into the system's analytical column whereas high boilers were kept in the pre-column that was swept backwards 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 numerous productivity advantages, including increased sensitivity, time and cost savings, easy maintenance, increased column lifetime and higher robustness of the entire analytical system.