Micro-SPE method for sample introduction in capillary HPLC/MS

A new solid-phase extraction on-line device for micro-HPLC is presented, This device optimizes the injection of very dilute samples into a packed capillary column. It consists of two capillary, reversed-phase, HPLC columns of different length that can be linked together as a single chromatographic column. The first segment, only 2 cm long is connected to the HPLC injector. When disconnected from the longer column, several milliliters of an aqueous sample can be passed through at a high now rate for fast trapping. On the basis of the retention mechanism, all suitable compounds are focused on the short column head in a sharp band. As soon as the chromatographic column is recomposed, the trapped analytes are eluted and separated at the optimal flow rate and gradient conditions. Due to the high preconcentration factor, trace-level analysis can be performed successfully. Different classes of analytes of various polarities and molecular weights can be determined, depending on the stationary phase and on the detector used, Some pesticides belonging to different classes were chosen to evaluate the performance of the device using an electron ionization mass spectrometer as HPLC detector, A fungicide in an irrigation canal water was determined at a concentration level of 4.5 mu .gL(-1).