Solid‐Phase Extraction Device Coupled to a Microcolumn Liquid Chromatograph with a UV Detector for Determining Estrogens in Water Samples

Abstract

A solid‐phase extraction (SPE) device in conjunction with a microcolumn liquid chromatograph with a UV absorbance detector was developed for determination of estrogens in water samples. The SPE device consisted of a syringe filter unit containing 3 mg of triacontyl (C30)‐bonded phase (15–30 µm particle diameter) and an LC syringe needle. Analytes were extracted onto the sorbent by passing the sample from a syringe (tens mL volume) to the device. To perform analyte desorption, the syringe was replaced by a microliter syringe that contained ethanol serving as the desorption solvent. After the device was installed in the needle port of an LC injection valve equipped with an external sample loop (200 µL volume), by passing the desorption solvent through the SPE device, the analytes were desorbed from the sorbent into the sample loop. The contents of the sample loop were transferred into the column by turning the valve from load to injection position. Separations were performed on a C30 column under isocratic conditions using an aqueous ethanol solution as the mobile phase. Bandbroadening problems resulting from such a large sample loading on the microcolumn were circumvented by use of water plugs placed before and behind the ethanol extract in the sample loop. Recoveries of 92.6–96.3 and preconcentration (enrichment) factors of 1852–1926 were achieved for the estrogens studied (estradiol, estriol, estron, and ethynyl estradiol). Limits of detection for the estrogens were 3.8–12.6 ng/L.