An in-line SPE strategy to enhance sensitivity in CE for the determination of pharmaceutical compounds in river water samples

In this study, the suitability of solid-phase extraction (SPE) coupled in-line to CE with UV-Vis detection was evaluated for the preconcentration and separation of diluted solutions of five pharmaceuticals compounds: benzafibrate, piroxicam, diclofenac sodium, naproxen and clofibric acid. An SPE analyte concentrator containing Oasis (R) HLB sorbent was constructed without frits and placed near the inlet end of the separation capillary. Different parameters such as sample pH, composition and volume of the elution plug and sample loading time were studied in order to obtain the maximum preconcentration factors. The LODs reached for standard samples were in the range 0.06-0.5 ng/mL with good reproducibility, and the developed strategy provides sensitivity enhancement factors around 14 000-fold in peak area and 5900-fold in peak height compared with the normal hydrodynamic injection. Finally, river water samples fortified with the pharmaceutical compounds were analyzed by the developed in-line SPE-CE-UV method in order to show the potential of the methodology for the analysis of environmental aquatic samples. For these samples, high values of relative recoveries, between 73-107% and 79-103% for two concentration levels, 5 and 25 ng/mL, respectively, were obtained and LODs ranged between 0.19 and 1 ng/mL.