Preparation of 4,4′-(1-[2H6]methylethylidene)bis-[2,3,5,6-2H4]phenol and its application to the measurement of bisphenol A in beverages by stable isotope dilution mass spectrometry

The preparation of 4,4′-(1-[2H6]methylethylidene)bis-[2,3,5,6-2H4]phenol, bisphenol A-d14, was achieved in excellent yield by reaction of [2H6]acetone with [2H6]phenol in the presence of deuterium chloride. The product thus obtained was shown by mass spectroscopy to be a mixture of the 2H14, 2H13 and 2H12 isotopomers in the relative proportions of 82.3:16.2:1.5, respectively. An isotope dilution gas chromatography–mass spectrometric method using bisphenol A-d14 as an internal standard was developed to measure the level of bisphenol A in beverages. The procedure involves extracting bisphenol A into dichloromethane, and then purifying the analyte by back extraction into dilute aqueous sodium hydroxide. Conversion of bisphenol A and its internal standard, bisphenol A-d14, to their corresponding O-bis(trifluoroacetyl) derivatives by treatment with trifluoroacetic anhydride gave compounds with good chromatographic properties and whose mass fragmentomerty is such that loss of M−CH3 and M−C2H3 are the base peaks in the mass spectra of the analyte and internal standard, respectively. Quantification of bisphenol A was achieved by comparing the area of the M−15 ion to that of the corresponding ion of bisphenol A-d14. The characteristics of our assay are: an analyte recovery of better than 95%, a root mean square signal-to-noise ratio of 79:1 for 1.7 pg on column and an inter-assay RSD of better than 4% (n=5).