On-line precolumn enrichment of bisphenol A using boronate column in microcolumn liquid chromatography

The application of a boronate precolumn in the trace determination of 4,4'-isopropylidenediphenol (bisphenol A or BPA) in aqueous solution was investigated by microcolumn liquid chromatography (LC). BPA was enriched by a precolumn packed with TSK(gel) boronate and it was then injected (back-flushed) into an ODS separation column. Comparing to a conventional syringe injection, a better peak shape was obtained via the boronate precolumn injection, and the calculated theoretical plate number improvement was approximately two folds. The relative standard deviations for the retention time, peak area and peak height were 0.12, 3.0 and 1.8%, respectively. The system is linear (R2>0.99) within the working sample concentration and sample-volume ranges, and it presents a detection limit of 0.09 microg L(-1)(S/N=3) when a 0.2 mL sample was enriched. Recovery values of the proposed method were between 107 and 123%, and this method was applied satisfactorily to the determination of BPA in commercially available bottled drink samples. The boronate precolumn was proven to produce better sensitivity than that of an ODS or C30 precolumn as long as the enrichment of BPA in aqueous samples is concerned.