Several weeks ago, Watabe et al. published an article in the Journal of Chromatography on ultra-low level detection of bisphenol A (BPA) in environmental water [1]. BPA is a known endocrine distruptor and the center of brewing controversy regarding the use of polycarbonate material. Watabe et al. implemented high-performance liquid chromatography (HPLC) to achieve a sensitivity of 0.36 ng/L. This method was used to probe environmental water and purified water samples containing 2-70 ng/L of BPA.
The article itself is quite in depth, and worth a bit more reading. One thing that piqued my interested while skimming was
For ultra-low concentration of BPA analysis, BPA contamination from manual pretreatment procedures as well as adhesive for fixing needle of manual syringes affects the determination seriously. This means manual syringes cannot be applied to BPA microanalysis. To obtain reliable quantitative results at ppt concentration level, a column switching auto pretreatment system is essential.Even employing this HPLC system, we unexpectedly encounter serious contamination problem due to BPA existing in purified water. A water purification system cannot remove BPA completely. A few ng/l level of BPA contamination often found in the purified water is not negligible and the contamination level varied daily. Consequently, there is no reliable way to correct a degree of contamination by calculation.
We have to obtain BPA-free water for preparing BPA standard solution otherwise reliable calibration curve cannot be created. BPA-free water was obtained by filtrating the purified water through Empore disk. Then the contamination was suppressed below the detection limit afforded by this HPLC system. Standard aqueous solution of BPA at 1, 10, and 100 ng/l were injected repeatedly (n=5) to estimate the repeatability of peak area and the results were shown in Table 1. A linear calibration curve with a correlation coefficient >0.999 was obtained. The recovery at 100 ng/l was 100.5% and even a trace of leaking and/or carry-over of BPA was not observed at same concentration. The detection limit estimated by utilizing standard deviation of y-intercept of calibration curves was 0.36 ng/l, which is quite low concentration.
References
[1] Y. Watabe, T. Kondo, M. Morita, N. Tanaka, J. Haginaka and K. Hosoya, "Determination of bisphenol A in environmental water at ultra-low level by high-performance liquid chromatography with an effective on-line pretreatment device," J.Chromatogr.A, vol. 1032, pp. 45-49, Apr 2. 2004.