Measurement of inositol in uremic serum by selected ion monitoring.

A highly sensitive and specific quantitative assay for inositol in serum has been developed. Uremic serum, to which hexahydroxybenzene as an internal standard was added, was deproteined with trichloroacetate. The supernatant aqueous phase was taken after lipids in serum were removed with chloroform, and was lyophilized. The dried powder was converted to butylboronate derivatives by reaction with 5% n-butylboronate (pyridine solution). The reaction mixture was gas chromatographed on fused silica megabore column DB-1, and assayed by electron impact mass spectrometry using selected ion monitoring. Inositol was quantified by the internal standard method. It was possible to determine concentrations as low as 0.1 microgram/ml in 0.5 ml of serum sample with a relative standard deviation of less than 5%. The serum inositol concentration from fifteen fasting patients with chronic renal failure was 39.1 +/- 18.2 micrograms/ml, significantly higher than that of control subjects (5.1 +/- 2.1 micrograms/ml). In the fifteen fasting patients, serum inositol was linearly related to blood urea nitrogen (r = 0.96).