CONDITIONS FOR SOLID-PHASE EXTRACTION OF URINARY BILE-ACIDS WITH OCTADECYLSILANE-BONDED SILICA

Fast atom bombardment mass spectrometry was used as a detection method in a study of the extraction of urinary bile acids with octadecylsila ne-bonded silica. The procedure commonly used in many laboratories was found to result in significant losses of sulfated taurine-conjugated bile acids. Losses of other double conjugates and of bile acid and bil e alcohol glucuronides were also seen. The losses were avoided by addi tion of an equal volume of 0.5 M triethylamine sulfate to the urine be fore passing it through the sorbent bed. Quantitative elution was then achieved with methanol. Batch variations were observed with sorbents from two different manufacturers.