Determination of nonsteroidal anti-inflammatory drugs in biological fluidsby automatic on-line integration of solid-phase extraction and capillary electrophoresis

A new, automatic method for the clean-up, preconcentration, separation, and quantitation of nonsteroidal anti-inflammatory drugs (NSAIDs) in biologica l samples (human urine and serum) using solid-phase extraction coupled on-l ine to capillary electrophoresis is proposed. Automatic pretreatment is car ried out by using a continuous flow system operating simultaneously with th e capillary electrophoresis equipment, to which it is linked via a laborato ry-made mechanical arm. This integrated system is controlled by an electron ic interface governed via a program developed in GWBasic. Capillary electro phoresis is conducted by using a separation buffer consisting of 20 mM NaHP O4, 20 mM beta -cyclodextrin and 50 mM SDS at pH 9.0, an applied potential of 20 kV and a temperature of 20 degreesC. The analysis time is 10 min and the detection limits were between 0.88 and 1.71 mug mL(-1). Automatic clean -up and preconcentration is accomplished by using a C-18 minicolumn and 75% methanol as eluent. The limit of detection of NSAIDs can be up to 400-fold improved when using sample clean-up. The extraction efficiency for these c ompounds is between 71.1 and 109.7 mug mL(-1) (RSD 2.0-7.7%) for urine samp les and from 77.2 to 107.1 mug mL(-1) (RSD 3.5-7.1%) for serum samples.