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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 (C 30 )‐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 C 30 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. [ABSTRACT FROM AUTHOR]

Split flow and bypass flow systems were assembled using Nano Y Connectors with low dead volume commercially available for capillary liquid chromatography (LC). The split ratio could be controlled by changing the dimension of restriction tubing and applied back pressure to the restriction tubing. The split flow system allowed us to use valve injectors and pumps commercially available for capillary LC. The reproducibility of the present split flow system was acceptable. The relative standard deviation for six successive measurements was 0.4% for the retention time, whereas that for the peak height and peak area was 1–3% depending on the analytes. The bypass flow system uses two Nano Y Connectors, where the eluent split at the first Nano Y Connector, which is located in the inlet of the separation column, is merged again into the effluent from the column at the second Nano Y Connector. The bypass flow system could avoid on-column detection and allowed us to use flow cells, leading to an approximate three times improvement in signal-to-noise. The present flow systems were evaluated by using aromatic hydrocarbons and alkylbenzenes as test analytes. [Copyright &y& Elsevier]