FY 1993

WOCE 1991 chlorofluorocarbon standard intercomparison report

Bullister, J.L., F. Menzia, and D.P. Wisegarver

NOAA Data Report ERL PMEL-45, NTIS: PB93-234326, 65 pp (1993)

A chlorofluorocarbon (CFC) standard intercomparison study was done among ten laboratories involved in measurements of dissolved and atmospheric CFCs as part of the World Ocean Circulation Experiment (WOCE) and other programs. The goal of this study was to compare CFC calibration scales and to allow CFC data sets collected by the participating groups to be merged together more easily. To prepare intercomparison gas samples, aliquots of dry air from a high pressure gas cylinder were transferred into a set of evacuated, high-purity gas cylinders and analyzed at PMEL for uniformity. One cylinder was distributed to each participating laboratory for analysis and return to PMEL. Within the precision of the analytical techniques used at PMEL, the CFC-11 and CFC-12 concentrations in the cylinders remained uniform throughout the intercomparison exercise. The CFC-113 and carbon tetrachloride content of the cylinders remained relatively uniform in all but one of the cylinders analyzed. The CFC-11 concentrations reported by participating laboratories ranged from 258.8 to 275.6 parts-per-trillion (PPT). The reported CFC-12 concentrations ranged from 487.4 to 503.5 PPT. Two laboratories reported values for CFC-113, and only one laboratory reported a value for carbon tetrachloride. Details of the calibration techniques used by the ten participating laboratories are given in the Appendices of this report.