Multiresidue method for determination of post emergence herbicides in water by HPLC/ESI/MS in positive ionization mode

A post-emergence (POE) herbicide can be defined as a foliage-applied product used to control weeds that have emerged in competition with the developing crop. We developed a sensitive and specific multiresidue method, based on reversed-phase liquid chromatography/mass spectrometry, with an electrospray interface (LC/ESI/MS), for determining 15 of most representative compounds of a new class of POE herbicides in water samples. The procedure used involved passing 2 L of groundwater and 4 L of drinking water samples, respectively, through a 0.5 g graphitized carbon black (GCB) extraction cartridge. A conventional 4.6 mm i.d. reversed-phase LC C-18 column, operating with a mobile phase flow rate of 1 mL/min, was used to chromatograph the analytes. A flow of 200 mu L/min of the column effluent was diverted to the ESI source. The study demonstrates the sensitivity of the technique, with detection limit under 5 ng/L in drinking water samples. Performance data for the method such as recovery and precision are also reported.