CALIBRATION OF ISOTOPE RATIO MASS-SPECTROMETRY WORKING STANDARD FOR H-2 H-1 RATIO ANALYSIS/

APE is the atom percent excess. It was found that the determined r(WR) had a precision of +/-1% Most of the variation came from sample handl ing, which includes the serial dilution of the weighed deuterium oxide , the reduction of water to hydrogen gas and the introduction of the h ydrogen gas into the mass spectrometer. The use of this calibration pr ocedure allows the direct determination of the isotope ratio r(SA), an d APE from a standard curve over a wide range of enrichment. Unlike th e reference standards V-SMOW and SLAP, the highly purified deuterium o xide is non-exhaustible and readily available. The highly purified deu terium oxide should be used in place of secondary standards to calibra te working references for H-2/H-1 analysis in biological studies. (C) 1998 John Wiley & Sons, Ltd.