Boismenu D, Robitaille L, Hamadeh M J, Hongsprabhas P, Hoffer L J, Mamer O A
The Biomedical Mass Spectrometry Unit, McGill University, 1130 Pine Avenue West, Montreal, Quebec, Canada H3A 1A3.
Anal Biochem. 1998 Jul 15;261(1):93-9. doi: 10.1006/abio.1998.2715.
A reproducible and very sensitive method is described for the quantitation of inorganic sulfate in biological fluids by negative electrospray ionization tandem mass spectrometry. After addition to the sample of (34)S-labeled sodium sulfate internal standard and deproteinization with methanol, interfering bicarbonate anions are removed by acidification and chloride and phosphate by means of a single filtration step. The tandem mass spectrometer is used in neutral loss mode to detect HSO(4)(-) ions free of interference from residual isobaric H(2)PO(4)(-) ions. Organic sulfates do not interfere with the measurement. Serum and urinary inorganic sulfate concentrations measured with this technique agree closely with determinations by ion-exchange chromatography with conductivity detection. Unlike the latter method, this technique does not require dedicated equipment. The method is also suitable for measuring the ratio of (34)S-labeled sulfate to unlabeled sulfate in serum and hence represents an attractive alternative for the use of the radioactive (35)S isotope in human studies of body composition and oxidation of sulfur-containing substrates to sulfate.
