A novel on-line sample clean-up and trace enrichment technique was developed for determination of pesticides in fruits and vegetables utilizing liquid chromatography tandem mass spectrometry. This technique uses an on-line solid phase extraction cartridge and column-switching device to reduce tedious off-line wet chemistry operations. The efficiency and recovery of sample preparation is significantly improved.
One hundred and five pesticides with a wide variety of chemical properties are included in the method development of determination of multiresidue pesticides in apple, cucumber, spinach, and tomato. A universal reversed phase high performance liquid chromatography method was used as a separation technique. An Atmospheric Pressure Chemical Ionization (APCI) interface coupled to a triple quadrupole mass spectrometer was employed for detection and quantitation. The ionization mechanisms of the pesticides with different chemical properties in the APCI ion source are discussed. A sensitive multiresidue pesticide screening method using selective ion monitoring (SIM) and selective reaction monitoring techniques (SRM) in both positive and