Comparison of tandem-in-space and tandem-in-time mass spectrometry in gas chromatography determination of pesticides:: Application to simple and complex food samples

Gas chromatography coupled to tandem mass spectrometry (GC-MS/MS) is one of the most powerful techniques in pesticide residue analysis. MS/MS can be conceived in two ways: tandem in space(e.g. triple quadrupole. QqQ) or in time (e.g. ion trap, IT). QqQ and IT are commonly interfaced to GC; however, there has not been any direct comparison between them in pesticide residue analysis so far. In the present work, the performance of GC coupled to these two analyzers (GC-QqQ-MS/MS and GC-IT-MS/MS) was studied and compared for pesticide residue analysis as well as its application in food analysis. The large Volume injection (LVI) technique together with programmed-temperature vaporization (PTV) was applied. For this purpose, 19 pesticides, including organochlorine and organophophorus pesticides and pyrethroids, were analyzed in both systems. Mass spectrometric data, performance characteristics (linearity, intra-day and inter-clay precision) and the influence of the matrix nature on the analysis of low concentrations were compared. The target compounds were analyzed in solvent and in two representative food matrices Such as cucumber (high water content) and egg (high fat content). MS data and intra-day precision were similar in QqQ and IT, whereas inter-day precision was significantly worse in Q(IQ. Linearity (expressed as determination coefficient, R-2 in the range 10-150 mu g L-1 was adequate in both systems: however, better R-2 values were obtained with the QqQ analyzer in high and low concentration ranges (1-50 and 1-750 mu g L-1, respectively). The influence of the matrix nature on the analysis of low concentrations of each analyzer was also evaluated. The QqQ and IT performance was similar in cucumber and solvent. However, QqQ provided better sensitivity in egg working in selected reaction monitoring (SRM). (C) 2008 Elsevier B.V. All rights reserved.