( injection was 15 min. ...)Simultaneous Determination of Residues of Approximately 100 Pesticides ,,, and Metabolites in Fruit and Vegetables by LC/MS/MS

ESI versus APCI

Using the optimized MRM transitions and identical sample amounts only 8 pesticides (propoxur, carbofuran, bendiocarb, carbaryl, tebuconazole, amidosulfuron, atrazine, and promecarb) out of 74 tested gave higher signal intensities with APCI+ under the conditions applied. The other 66 gave a better response with ESI+. Therefore, the TurboIonSpray source was used here.

Number of simultaneously detectable MRM transitions

As demonstrated in Figure 3, a dwell time reduction down to 25 ms is accompanied with only a minor reduction in signal intensity. The signal to noise ratio decreases in the worst two cases to about 40% of the 100 ms value. However, this still compares to a sufficient S/N ratio. Consequently,

with 25 ms dwell time and a pause between mass ranges of 5 ms within the cycle time of 3 seconds the simultaneous measurement of 100 MRM transitions. The signal to noise ratio decreases in the worst two cases to about 40% of the 100 ms value. However, this still compares to a sufficient S/N ratio. Consequently, with 25 ms dwell time and a pause between mass ranges of 5 ms within the cycle time of 3 seconds the simultaneous measurement of 100 MRM transitions is possible. In cases, where one deals with sufficiently high concentrations, even measurements with a minimum dwell time of 10 ms should be possible, allowing the simultaneous detection of about 200 MRM transitions using an LC/MS/MS system with a LINAC collision cell. However, the parallel measurement of positive and negative ions in one run should be avoided because of the necessary stabilization of the changed polarity
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