No abstract

No abstract

A gas chromatographic chemical ionization mass spectrometric assay has been developed to measure carprofen in blood. The method features the addition of either a structural or stable isotope analog internal standard to plasma prior to a simple benzene extraction at pH 4.5. The residue, after removal of the benzene, is methylated with ethereal diazomethane. Following evaporation of the methylating solvents, a portion of the reconstituted residue is analyzed by gas chromatography mass spectrometry. The mass spectrometer is set to monitor in the gas chromatographic effluent the [MH]+ ions of carprofen methyl ester and the methyl ester of the internal standard generated by isobutane chemical ionization. Assay sensitivity is 5 pmol ml-1. When 200 pmol ml-1 samples are analyzed using a stable isotope analog as the internal standard, the precision and accuracy are both 4%. Using a structural analog as the internal standard, the assay was neither as precise nor as accurate.

Ura~i1-6-'~C (21. prepared i n high radiochemical yield by conventional methods, has been converted t o 5-fluorouracil-6-I 4 C (91 i n over 90% yield using trifZuoromethythypofluorite. The use of t h i s recently introduced reagent eliminates the necessity of preparing 9 from fluorinated precursors.

The sulfonamide potentiator ormetoprim (6) has been prepared with a carbon-14 label for use in biolo ical studies.