Biomonitoring of biphenol a and bisphenol s in urine using liquid chromatography-mass spectrometry

As an essential component of polycarbonate plastics and epoxy resins, Bisphenol A (BPA) is found in numerous industrial and consumer products, including electronic goods, household equipment, metallic food and beverage cans, bottles and dental devices. BPA is also used in the production of thermal paper. BPA may cause adverse health effects because of its estrogenics properties. The widespread occurrence of BPA in environment and consumer urines has raised concerns among regulatory agencies all over the world. BPA is being replaced with a number of alternatives, such Bisphenol S (BPS). Limited studies have shown that BPS possess estrogenic activity similar to BPA. In humans, BPA is metabolized in the liver to its glucuronide forms and eliminate mainly through urine. A quantification of free and conjugated forms of BPA in urine is thus a valuable tool for the assessment of human exposure. The objective of this work was to develop accurate methods for the determination of free and total BPA and BPS in urine samples, using liquid chromatography tandem mass spectrometry (LC-MS/MS).
Conjugated BPA and BPS were hydrolysed enzymatically from urine to release free forms. BPA was extracted with toluene and derivatized with dansyl chloride before analysis. The extraction procedure for BPS was different due to its high polarity. Urine samples were purified by solid phase extraction on Oasis MCX cartridge before derivatization by dansyl chloride (Fox et al. 2011). The liquid chromatography separation was performed in a reversed-phase column and BPA-d6 was chosen as internal standard. BPA and BPS dansyl derivatives were thus analyzed by LC-MS/MS operating in positive mode. The validation criteria of methods were assessed in pools of spiked urine samples.
Calibrations were linear up to 20 µg/l with a limit of quantification of 0.1 µg/l. Methods were shown to be selective, reproducible, accurate and complied with good laboratory practices. Exogenous contamination due to leaching of BPA from the materials and solvent contamination was minimized. Background levels of BPA and BPS from the overall procedure were determined before each run. These methods allowed also the determination of glucuronide forms of BPA and BPS in urine samples.
On account to its sensitivity, our methods are thus suitable for biomonitoring of occupational exposure to BPA and BPS in different settings including epoxy resin factories or sales area where thermal paper are frequently handled. The assessment of occupational exposures is in progress.

Fox S.D., Falk R.T., Veenstra T.D. and Issaq H.J. (2011), J. Sep. Sci., 34, 1268-1274.