A highly sensitive HPLC method was developed for the determination of xenoestrogenic compound, bisphenol A (BPA) in human breast milk samples. After a two-step liquid-liquid extraction, BPA was derivatized with fluorescent labeling reagent, 4-(4,5-diphenyl-1H-imidazol-2-yl)benzoyl chloride (DIB-Cl). The excess fluorescent reagent could be removed effectively using a column-switching system. The separation of DIB-BPA from endogenous materials in milk was carried out on two C(18) columns and fluorescence intensity was monitored at 475 nm with the excitation of 350 nm. A good linearity (r = 0.994) was observed of BPA in the concentration range of 0.2-5.0 ng mL(-1) in breast milk, and the detection limit was 0.11 ng mL(-1) at a signal-to-noise ratio of 3. Intra- and inter-day precision (RSD, %) were less than 8.7 and 10.4, respectively. Twenty-three breast milk samples of healthy lactating women were analyzed for the BPA concentration; the mean value was 0.61 +/- 0.20 ng mL(-1), with no correlation to the lipid content of milk samples.

A rapid and simple method for the determination of anionic surfactants in tap water has been developed. The official analytical method in Japan for the determination of anionic surfactants in tap water requires tedious procedures and requires large amounts of chloroform as the extract solvent; it was greatly improved by the present spectrophotometric method using Methylene Blue. Our present method requires only one half of sample (50 ml), one tenth of the extraction solvent (chloroform=5 ml), and one sixth of the analytical time compared with the official analytical method.

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The free energy changes (ΔG) for the reaction B2Li+ = Li+ + 2B were obtained in the gas phase for m- and p-substituted acetophenones based on the measurement of ligand-exchange equilibria of the type LiA2+ + 2B = LiB2+ + 2A using a FT-ICR spectrometer. A plot of ΔG (relative lithium cation basicity, ΔLCB[B2Li+]) values against the ΔGB (proton basicity) showed a limited linear correlation for meta substituents and para electron-withdrawing groups with a slope of 1.06. Negative deviations observed for strong π-donor susbstituents suggested that the resonance effect of these substituents is reduced in the Li+ complex compared to that in the protonated ion. Based on the correlation analysis using the Yukawa–Tsuno equation, , the substituent effect on ΔLCB[B2Li+] of acetophenone was characterized by a ρ value of −12.5 and an r+ value of 0.49. A ρ value of −8.3 was determined for ΔLCB[BLi+] based on the reaction LiB+ = Li+ + B from a ρ value for ΔLCB[B2Li+] by using a factor of 1.5 that was obtained from a linear relationship between calculated ΔLCB[B2Li+] and ΔLCB[BLi+]. In comparison with the corresponding results for other Lewis cation basicities, it was shown that the ρ value decreases in the order of H+ (−11.6) > Me3Si+ (−11.0) > Me3Ge+ (−9.7) > Li+ (−8.3). The decrease in the ρ value indicates that the positive charges at the Lewis cation moiety of the adduct ion increases in this order. The small ρ value for the Li+ basicity is consistent with largely ionic (ion–dipole interaction) nature of the bonding interaction between Li+ and the carbonyl oxygen atom. The r+ value that indicates the degree of charge-delocalization into the aromatic π-system also decreases in the same order. In spite of a small charge transfer from Li+ to acetophenone ligand, the moderate r+ value of 0.49 observed for the Li+ complex is interpreted to be due to the redistribution of the induced positive charge in the acetophenone moiety by binding with Li+.

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