Phytoestrogen biomonitoring: an extractionless LC-MS/MS method for measuring urinary isoflavones and lignans by use of atmospheric pressure photoionization (APPI)
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We present here a high-performance liquid chromatography−tandem mass spectrometry (LC-MS/MS) method for quantifying phytoestrogenic isoflavones (daidzein, equol, genistein, and O-desmethylangolensin) and lignans (enterodiol and enterolactone) in urine without the use of extraction or the preconcentration techniques inherent in existing methods. The development of this concept was made possible by use of atmospheric pressure photoionization (APPI); an ionization technique that we found to improve analyte sensitivity relative to electrospray ionization and atmospheric pressure chemical ionization for this particular group of compounds. The analytical performance of this method was equal to or exceeded that of comparable methods. Between-run coefficients of variation (CVs) across three quality control (QC) pool levels analyzed in duplicate over 20 days were 3.1–5.8% CV; within-run CVs were 2.3–6.0%. Accuracy, as determined by average spike recovery in QC pools, was generally within ±10% of being quantitative (100%). Relative limits of detection were 0.04–0.4 ng/mL urine, with absolute detection limits as low as 0.1 pg. This method was applied to the analysis of >2,500 urine specimens for the 2005–2006 Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey (NHANES). The method was capable of quantifying these compounds in 95–100% of study samples. This work is the first ever report of using APPI for the LC-MS/MS determination of these compounds in urine. It is also the first method of its kind to do so without any need for analyte extraction or preconcentration prior to analysis.
KeywordsIsoflavones Lignans Phytoestrogens Urine Atmospheric pressure photoionization Electrospray Mass spectrometry ESI APCI APPI
We gratefully acknowledge Donna J. LaVoie, M.T. (A.S.C.P) and David T. Nguyen, B.S., who conducted many of the experiments and analyses associated with this project. We would also like to pay special tribute to Nigel P. Botting, PhD, who sadly passed away this year. We owe a good deal of our success in developing and implementing quality methods for assessing phytoestrogen exposure to Nigel and the efforts of his research group at the University of St. Andrews to provide consistently high-quality analyte and internal standards. He will be dearly missed.
- 13.Grynkiewicz G, Ksyciańska H, Ramza J, Zagrodzka J (2005) Chromatographic quantification of isoflavones (why and how). Acta Chromatogr 15:31–65Google Scholar
- 17.Locati D, Morandi S, Cupisti A, Ghiadoni L, Arnold A (2005) Characterization and quantification of soy isoflavone metabolites in serum of renal transplanted patients by high-performance liquid chromatography/electrospray ionization mass spectrometry. Rapid Comm Mass Spectrom 22:229–234Google Scholar
- 23.Kuklenyik Z, Ye XY, Reich JA, Needham LL, Calafat AM (2004) Automated online and off-line solid-phase extraction methods for measuring isoflavones and lignans in urine. J Chromatogr Sci 42:495–500Google Scholar
- 25.National Health and Nutrition Examination Survey (2011) U.S. Centers for Disease Control and Prevention, Atlanta. http://www.cdc.gov/nchs/nhanes.htm. Accessed 19 July 2011
- 28.Syage JA, Short LC, Cai S-S (2008) Atmospheric pressure photoionization—the second source for LC-MS? LC GC N Am 26:286+Google Scholar
- 31.Taylor JK (1987) Quality assurance of chemical measurement. Lewis, Boca RatonGoogle Scholar
- 34.Yoshioka N, Akiyama Y, Teranishi K (2004) Rapid simultaneous determination of o-phenylphenol, diphenyl, thiabendazole, imazalil and its major metabolite in citrus fruits by liquid chromatography–mass spectrometry using atmospheric pressure photoionization. J Chromatogr A 1022:145–150CrossRefGoogle Scholar
- 37.Clarke DB, Lloyd AS, Botting NP, Oldfield MF, Needs PF, Wiseman H (2002) Measurement of intact sulfate and glucuronide phytoestrogen conjugates in human urine using isotope dilution liquid chromatography–tandem mass spectrometry with [13C3]isoflavone internal standards. Anal Biochem 309:158–172CrossRefGoogle Scholar
- 38.Martin RF (2000) General Deming regression for estimating systematic bias and its confidence interval in method-comparison studies. Clin Chem 46:100–104Google Scholar