Chapter 9 - Application of GC–TOFMS for Pesticide Residue Analysis in Grapes

Abstract

Abstract Management of pesticide residues in food is a major public concern that influences the strategies of crop protection. The emphasis on food quality and safety has prompted the development of several stringent legislations, which are particularly important for grape and its processed products, since they are often consumed worldwide in raw form or after minimal processing. Grape cultivation is associated with frequent applications of agrochemicals, and the introduction of newer compounds in market as well as the differences in the lists of monitoring chemicals across different countries is a critical issue that influences the success of residue monitoring programs for facilitation of international trade. Thus, target-oriented residue monitoring by tandem mass spectrometry (MS/MS) or selected ion monitoring (SIM) often fails to provide holistic assessment of the contamination status in a sample and often appears as a major limitation complicating international trade decisions. Analysis of agrochemical residues by time-of-flight (TOF) MS can have multiple benefits. The technique has the potential to perform nontarget analysis of a large number of compounds within a short time period with sufficient accuracy. Simultaneously, comprehensive GC × GC has emerged as a powerful separation technique in complex sample matrixes. In general, the sensitivity of analysis improves significantly in thermally modulated GC × GC–TOFMS as compared to that obtained by GC–TOFMS. The chapter describes the factors and steps involved in obtaining a sufficiently resolved GC × GC chromatogram along with the application in determining trace level pesticide residues from grape and processed products. The parameters requiring optimization are injection techniques, column selection and combination, ion source temperatures, spectral acquisition rates, carrier gas flow rates, temperature program, modulation, and duration of pulses. The chapter describes the optimization of the separation and detection conditions leading to separation of 185 analytes extracted from grape and processed products for accurate identification and quantification. In addition to pesticide residues, a large number of matrix coextractives, for example, ethyl hexyl cinnamate, butyric acid, γ-tocopherol, 4-hydroxybenzaldehyde, myristic acid, ethyl myristate, palmitic acid, etc., could be identified based on automated library searching using NIST database. The optimized method was successfully applied in screening grape, wine, and juice samples.