Patent ID: 6138497
Filing Date: 2000-10-31
Classification: G01N

Abstract:
A method for substantially simultaneously determining amounts of CO.sub.2, O.sub.2 and N.sub.2 gases dissolved in a liquid sample, comprising the steps of:(a) evacuating a sample cell, including a phosphorescent material capable of being excited by primary light to emit secondary light, via vacuum pressure;(b) extracting a gas sample from the liquid sample, the extracted gas sample then entering the evacuated sample cell;(c) transmitting infrared (IR) radiation, at at least one wavelength absorbed by CO.sub.2 gas, through the extracted gas sample in the sample cell;(d) transmitting primary light into the phosphorescent material in the sample cell;(e) measuring an amount of IR radiation absorbed as an indication of the concentration of CO.sub.2 gas in the gas sample;(f) measuring, substantially simultaneous to step (e), an amount of secondary light emitted by the phosphorescent material, quenched by O.sub.2 in the gas sample, as an indication of the concentration of O.sub.2 gas in the gas sample, the transmitted IR radiation and emitted secondary light traveling through the sample cell in substantially orthogonal directions;(g) measuring the total pressure of the gas sample;(h) measuring the temperature of the gas sample;(i) determining the partial pressure of CO.sub.2 gas from the absorbed amount of IR radiation measured in step (e) and the temperature measured in step (h);(j) determining the partial pressure of O.sub.2 gas from the amount of emitted secondary light measured in step (f) and the temperature measured in step (h);(k) subtracting the sum of the partial pressures of CO.sub.2 and O.sub.2 determined in steps (i) and (j) from the total pressure measured in step (g) to determine the partial pressure of N.sub.2 ; and(l) determining the concentration of CO.sub.2, O.sub.2 and N.sub.2 gases dissolved in the liquid sample from the respective partial pressures determined in steps (i), (j) and (k) and the temperature measured in step (h).