Objective: To establish a capillary electrophoresis-mass spectrometry(CE-MS) method for the analysis of nineteen organonitrogen pesticides in Paeoniae Radix Alba.
Methods: CE-MS analysis was performed on a 70 cm X 50 μm fused-silica capillary. The optimal buffer was composed of 1 % formic acid and 15 % methanol(V/V, pH 2.2). The temperature of capillary was controlled at 25 degree. The separation voltage was +20 kV. The optimal MS parameters were as follows: ESI-MS analysis was performed in the positive mode; 90 % methanol containing 0.2 % formic acid with a flow rate of 8 μl·min(-1) was selected as the sheath liquid; the flow rate and temperature of drying gas were 6 L·min(-1) and 250 degree, respectively; The nebulizing gas pressure was set at 5 psig; The optimal values of fragmentor and ESI voltage were 100 V and 5 000 V, respectively.
Results: The nineteen pesticides had good linearity over the testing ranges. The average recoveries were in the range of 80.1 %-108.4 % with RSDs less than 20 % (except ethoxyquin and spiroxamine, those of which were 29.2 % and 22.3 % at 0.01 mg.kg(-1) concentration level). The LODs of nineteen pesticides were 0.503 ≊10.1 μg.kg(-1).
Conclusion: The method can be used effectively to analyze the nineteen organonitrogen pesticides residue in Paeoniae Radix Alba.