Abstract/Summary

Organic pesticides are chemical compounds used to control pests and diseases that affect plants. Pesticides are hydrocarbon based and usually contain complex combinations of functional groups, heteroatoms and structural types. The organochlorine pesticides feature at least one, but normally many more C-Cl bonds. These pesticides are known to be stable, many incorporating multiple rings some of which are substituted benzene rings; one notorious example is DDT.Organochlorine pesticides have a significant half-life in the environment, which leads to accumulation in agricultural crops. The organophosphate pesticide class contains the phosphate functional group normally as a phosphate ester. This functional group makes them effective inhibitors of the acetylcholine esterase (AChE) enzyme class found in insects. As this enzyme class is critical to human health, organophosphates are known to have toxic effects in humans and animals. The presence of nitrogen in the composition of pesticides gives rise to the organonitrogen pesticide class usually typified by the presence of a carbamate functional group., This class is known to target and disrupt the nerve system of insects and other pests. The Pyrethroids are synthetic insecticides that are of a more traditional hydrocarbon formula, they are a class adapted from natural pyrethroids that cause hyperexcitability in the nerve cells of insects through binding to sodium channels. In the end, as with most ‘treatments’ combination therapy achieved through the use of multiple pesticides with different biological and physical properties leads to effective control but also serious questions around residual contamination of products entering the human food chain. Concerns around toxic compounds entering the food chain brings regulation and chemical analysis to the fore. Thus, gas chromatography (GC) with Mass spectrometry (MS) has been found to be particularly suitable for pesticide analysis, especially with modern high-precision instruments. In addition, the flexibility shown by Massspectrometry (MS) when using different ionisation methods allows for better coverage of a class of molecules that have distinctly different properties., Furthermore, the mass spectrometer can be coupled with gas chromatography allowing the sample components to be separated prior to MS analysis. In light of this, the development of mass spectrometry techniques for analysing a wide range of pesticides is important and will provide a more selective and more accurate methods of detection. In this work, the effectiveness of the mass spectrometry methodology in pesticide analysis using different devices such as GC-FID, GC-EI-ITQMS, GC-SICRIT-LTQMS, and GC-EI-MSD was evaluated. The emphasis of the study is on the effectiveness of a soft ionization source, recently commercialized (SICRIT) when compared to established electron ionization (EI) methods. The study compares and contrasts the use of SICRIT vs EI across a number of GC-MS setups for the detection and analysis of the organochlorine, organonitrogen, organophosphate and pyrethroid classes.