Statistical Evaluation Of Gas Chromatography For The Determination Of Dissolved Gases In Sea Water

Statistical Evaluation of Gas Chromatography for the Determination of Dissolved Gases in Sea Water

A gas chromatographic method developed by the authors for the determination of dissolved gases in sea water has been evaluated with respect to precision and accuracy by comparison with other methods. Both laboratory and shipboard measurements were employed in the evaluation. Dissolved oxygen analyses made at sea under routine conditions of operation over a period of two weeks indicate statistically significant differences in precision for the three methods tested: gas chromatography (plus or minus 1.8%), standard Winkler method (plus or minus 1.0%), and a modification of the Winkler method (plus or minus 0.51%). No significant bias was found between gas chromatography and the improved Winkler method; a small but statistically significant bias ( -1%) was found for the standard Winkler method relative to the other two. From a practical point of view, these differences are not considered important for routine survey operations. The dissolved N2 data obtained by gas chromatography are grouped about a mean value of 100% saturation, with approximately 95% of the values falling within (100 plus or minus 5)% saturation. The advantages of gas chromatography (routine analyses by relatively nonskilled personnel to obtain simultaneous measurements of more than one gas on a small volume of liquid) are felt to be sufficient to warrant its further use in oceanography. (Author).

Report of NRL Progress

Oceanography