Measurement of intact sulfate and glucuronide phytoestrogen conjugates in human urine using isotope dilution liquid chromatography-tandem mass spectrometry with [13C3]isoflavone internal standards - Clarke,D.B.; Lloyd,A.S.; Botting,N.P.; Oldfield,M.F.; Needs,P.W.; Wiseman,H. (Anal Biochem, 2002)