Measurement of bisphenol A levels in human urine.

We report a new approach for assessing human exposure to bisphenol A (BPA) by measuring BPA in urine after enzymatic deglucuronidation. This method involves addition of (13)C(12)-labeled BPA, enzymatic deconjugation, solid-phase extraction, and derivatization with pentafluorobenzyl bromide. The product of the derivatization is separated by gas chromatography followed by mass spectrometric detection using negative chemical ionization and selected ion monitoring. Using this analysis method, urine samples fortified with both a constant level of labeled BPA and a range of unlabeled BPA levels (0.27-10.6 ng/ml) demonstrated constant percentage recovery. In addition, a range of urine sample volumes (0.25-10.0 ml) with constant amounts of added internal standard produced a linear response (r(2)=0.99). The method limit of detection was 0.12 ng/ml. This method was validated by duplicate analyses using gas chromatography coupled to a high-resolution mass spectrometer.

Some considerations of methodology and standardization of apolipoprotein A-I immunoassays.

Apolipoprotein A-I (apo A-I) is the major protein of high-density lipoprotein. Compelling evidence suggests that measurement of concentrations of apo A-I in serum may be useful in predicting and assessing ischemic heart disease. The following review of methods of isolation, characterization, and assay of apo A-I has been developed to assess the possibility of standardizing apo A-I immunoassays. We consider the properties of apo A-I that have an effect on its quantification, such as self-association, polymorphism, and stability characteristics. We attempt to review critically the various methods presented, but more information about the physicochemical properties of the protein is required before definitive recommendations can be made.