Simultaneous Determination of Chlorofluorocarbons and Sulfur Hexafluoride in Seawater Based on a Purge and Trap Gas Chromatographic System

• Published in: Fēnxī huàxué 2016-07, Vol.44 (7), p.1003-1008
• Main Authors: CAI, Ming-Gang, DENG, Heng-Xiang, HUANG, Peng, KE, Hong-Wei, ZHENG, Xue-Hong, LI, Wen-Quan
• Format: Article
• Language: English
• Subjects: Chlorofluorocarbons; Desorption; Expeditions; Gas chromatography; Mathematical analysis; Oceans; Sea water; Sulfur hexafluoride
• ISSN: 1872-2040; 0253-3820
• DOI: 10.1016/S1872-2040(16)60941-6

Chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF sub(6)) are types of anthropogenic halogenated compounds, and are very important for ocean processes, including air-sea and water mass exchanges. Meanwhile, they can also be used to calculate some key physical and biogeochemical parameters such as the apparent oxygen utilization rate and anthropogenic CO sub(2). Compared to CFCs, SF sub(6) is quite difficult to measure in seawater due to its low solubility. However, it is useful to study the ocean processes based on both CFCs and SF sub(6). In this study, a purge and trap gas chromatography system was developed to simultaneously measure CFC-12 and SF sub(6) in seawater. The optimal conditions were as follows: trap temperature of -70 degree C, purge time of 8 min, purge gas pressure of 310 kPa, desorption time of 30 s, desorption temperature of 90 degree C. The method was simple and sensitive. The detection limit were 0.02 pmol kg super(-1) for CFC-12 and 0.03 fmol kg super(-1) for SF sub(6). The analytical precision of CFC-12 was plus or minus 1.2% and that of SF sub(6) was plus or minus 0.5%. The correlation coefficient (R super(2)) values of all calibration curves were greater than 0.9995. This method was successfully used in the analysis of sea water samples collected during the 6 super(th) Chinese Arctic Research Expedition.