A METHOD OF GAS CHROMATOGRAPHY FOR QUANTITATIVE ANALYSIS OF BLOOD-GASES BY

A gas chromatographic system for the quantitative analysis of blood-gases has been constructed. The system incorporates a simplified "equilibration " blood-gas extraction and injection unit, and adsorption columns linked in parallel. Eighty jul. of blood is required for each analysis. The time required to carry out duplicate analyses is 8 minutes. Blood oxygen, carbon dioxide and nitrous oxide contents are determined using peak height measurements. Calibration for carbon dioxide is carried out by using carbonate solution, for oxygen by using room air, and for nitrous oxide by using cylinder nitrous oxide. Reproducibility studies were carried out by analyzing one blood sample ten times: coefficients of variation for oxygen, carbon dioxide and nitrous oxide were, in each case, approximately 0.5 per cent. Comparisons of oxygen and carbon dioxide contents of twelve blood samples were simultaneously determined by the gas chromatographic method and by the Van Slyke manometric method. There was close agreement between the two methods; the coefficients of correlation of the respective estimations were +0.999 in the case of oxygen and +0.995 in the case of carbon dioxide. Analysis of blood-gases by a gas chromatographic technique involves four main stages: the extrac-tion of the gases from the blood using Van Slyke reagent and their subsequent injection on to the chromatographic columns; separation in the columns of the gas mixture into its individual components utilizing selective adsorption on solid adsorption media; detection of the individual gases by means of a katharometer utilizing thermal conductivity changes; and finally record-ing of the signals produced by the katharometer (fig. 1). The extraction of gases from the blood and their injection on to the columns in a reproducible manner has presented the most difficult technical problem encountered in this analytical technique. A "vacuum extraction " method has been des