PCT No. PCT/EP96/04384 Sec. 371 Date Aug. 24, 1998 Sec. 102(e) Date Aug. 24, 1998 PCT Filed Oct. 9, 1996 PCT Pub. No. WO97/14952 PCT Pub. Date Apr. 24, 1997A stable isotope analyzer is concentration calibrated by measuring relative proportions of isotopes in a measurement gas. The measurement gas is a component of a gaseous mixture consisting of the measurement gas and one other gas or a mixture of gases containing none of the measurement gas. First, a mixture is produced with a relatively high concentration of the measurement gas and known isotope proportions. The concentration of the measurement gas in the other gas is determined and the isotope proportion is measured to determine a point on a calibration curve (measured isotope proportion values vs. measured concentration values). At least one further point on the calibration curve is determined by diluting the measurement gas in the mixture by introducing a gas or gaseous mixture containing no measurement gas. The reduced concentration is determined and the isotope proportion measured to determine another point on the calibration curve. The steps of reducing the measurement gas concentration in the gaseous mixture, measuring the measurement gas concentration, and measuring the isotope proportion are preferably repeated a plurality of times to plot the calibration curve more accurately.
展开▼
