Determination of isotopically labelled monoesterphthalates in urine by high performance liquid chromatography-mass spectrometry.

A method of analysis for monoesters of phthalic acid ('monoesterphthalates') in human urine has been developed. The method was needed to determine the hydrolysis and excretion efficiency of isotopically-labelled phthalate diesters ('phthalates') when they were fed to volunteers as part of a biomarker study to estimate total exposure to phthalates. The targeted substances were 13C-monobutylphthalate (MBP), 2H4-monobutylphthalate (MBP), 2H4-monobenzylphthalate (MBeP), 13C-monocyclohexylphthalate (MCHP), 13C-monoethylhexylphthalate (MEHP), and 13C-monoisodecylphthalate (MIDP). The monoesters in urine were deconjugated enzymatically, extracted into solvent, and then determined by high performance liquid chromatography-mass spectrometry (LC-MS) using atmospheric pressure chemical ionisation in the negative ion mode. The limits of determination were 10 ng ml(-1) for MBP, MCHP, MBeP and MEHP, and 40 ng ml(-1) for MIDP. The recovery from urine spiked at 100 ng ml(-1) was in the range from 70 to 85% except for MIDP which was lower at 55%. The between-batch reproducibility of the analysis was in the range 8 to 17% (n = 6 batches on separate days).

Isoflavone aglycon and glucoconjugate content of high- and low-soy U.K. foods used in nutritional studies.

The isoflavone aglycon and glucoconjugate content of commercially prepared and "home-prepared" high- and low-soy foods selected for use in an on-going nutritional study were measured by LC-MS. The daidzin, daidzein, 6"-O-malonyldaidzin, 6"-O-acetyldaidzin, genistein, genistin, 6"-O-malonylgenistin, 6"-O-acetylgenistin, glycitin, glycitein, 6"-O-malonylglycitin, and 6"-O-acetylglycitin content are expressed in terms of individual isoflavones, total isoflavone equivalents, and milligrams of isoflavones per portion served. Soybeans (774 mg x kg(-1) total isoflavones) and soybean-containing foods had the highest isoflavone content of the foods examined. The low-soy foods all contained very low concentrations (<8 mg x kg(-1) total isoflavones) of the isoflavone aglycons and glucoconjugates. High- and low-soy 11 day rotating menus were constructed from the analyzed foods to deliver 100.0 and 0.5 mg of isoflavones per day, respectively.