( which needs approximately 700 ms. Thi...)Simultaneous Determination of Residues of Approximately 100 Pesticides ,,, and Metabolites in Fruit and Vegetables by LC/MS/MS

, which needs approximately 700 ms. This has to be done twice in an ESI+/ESI- sequence and therefore consuming about 50% of the total cycle time of 3 seconds. Figure 2 shows the simultaneous detection of 97 pesticides at the level of 0.025 mg/kg. The figure suffers from the overlay of so many traces. Therefore, a better demonstration of selectivity and sensitivity of MS/MS detection is given in Figure 4, which shows the acquired MRM traces of 12 selected analytes at 0.01 mg/kg level individually. Due to higher selectivity compared to chromatograms obtained with GC/MS in the Selected Ion Monitoring mode (SIM) significant matrix peaks are rare in LC/MS/MS, resulting in a more convenient detection and integration of relevant analyte peaks. Usually, retention time windows (periods) are used to enhance the individual dwell times and consequently the sensitivity of mass spectrometric detection. As shown in Figure 4 (and in the demo files given on the CD), such periods are unnecessary here, avoiding the resetting of switching times with new columns, other pumps etc. An example of a real sample with incurred residues is given in Figure 5, which shows the chromatogram of a lettuce extract with incurred residues.

Dependence of compound specific parameters on the type of MS/MS instrument

As mentioned above, the time consuming part in the development of a MS/MS method is the optimisation of six compound specific parameters for each analyte (totally 600 for 100 pesticides!). Therefore, the transformation of all compound specific parameters originally optimized for an API 2000 system was tested. This was done by the use of a tuning mixture, which contains 8 out of all 97 compounds (aldicarb, a
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