A procedure is described to quantitate inorganic phosphate in the form of the tris(trimethylsilyl) (TMS) phosphate by gas-liquid chromatography-mass spectrometry (glems) that increases the previously reported detection limit from the microgram to the nanogram range (i.e., 3 ng). The sensitivity for detecting TMS-phosphate by glc-ms analysis was shown to be limited by an increasing fractional loss with decreasing concentrations of TMS-phosphate analyzed due to its adsorption on different types of glc column supports. The method developed employs [ 18O 4]phosphoric acid which serves as both an internal standard to permit quantitation and as a carrier to minimize sample adsorption on the glc column support.