NSWC/WOL/TR 75-35 



A system based on this method has been developed by Swinnerton 

 et. all 5 ' 16 for the analysis of CO, CH4, N2 , 2 , and CO2 in seawater, 

 The equipment consists of an all-glass sample chamber in which the 

 dissolved gases are stripped from solution by an inert carrier gas 



(such as helium), a four-way by-pass valve, a commercially available 

 gas chromatograph, and a recorder- The stripped gases are dried and 

 passed to a gas partitioner consisting of two columns. The first 



(a 6 ft. x 1/4 in. column of 30% hexamethylphoramide on 60-80 mesh 

 column pack) separates CO2 from the mixture while the second (a 4 ft. 

 x 1/4 in. column of 60-80 mesh column pack followed by a 7 3/4 ft. 

 x 1/4 in. column of 40-60 mesh molecular sieve 13x) resolves the 

 O2, N2 # CH4, and CO. A thermal conductivity detector is used to 

 determine the separated gases. A schematic of the system is shown 



in Fig. 8. The system is calibrated using determinations on water 

 saturated with pure gases at a known temperature and pressure. 

 Sensitivities as low as 0.05 ppm in 30 ml samples can be obtained. 

 A chromatogram of a dissolved gas mixture in water is shown in 

 Fig. 9. 



Swinnerton and Linnenbom-'-^ have develop an extremely sensitive 

 gas chromatographic procedure for the determination of very low 

 concentrations of low molecular weight hydrocarbons in seawater 

 (C1-C4) . The hydrocarbons are stripped from about 1 liter of sea- 

 water with helium and after drying, collected in a series of two 

 cold traps. The first cold trap is a column of activated alumina 

 at -80°C (acetone-dry ice bath) which traps the C2-C4 hydrocarbons. 

 The second is a column of activated charcoal, at -80°C, which traps 

 the methane. Following a stripping period of 15 to 20 minutes the 

 temperature of the cold traps is raised to 90°C and the gases back 

 flushed with helium, from the traps into the gas chromatograph. 

 The methane is passed through a 4 ft. x 1/4 in. column of silica gel 

 while the C2-C4 hydrocarbons are resolved by either a 4 ft. x 3/16 in, 

 activated alumina column with 10% paraffin oil or a 10 ft. column 

 of chromosorb with 20% SF-96 (or SE-30) depending on whether 



15 



Swinnerton, J. W. , Linnenbom, V. J., and Cheek, C. H. , op cit, pg 37 



" Swinnerton, J. W., Linnenbom, V. J., and Cheek, C. H., "Revised 

 Sampling Procedure for Determination of Dissolved Gases in Solution 

 by Gas Chromatography", Anal. Chem. , 34, 1509 (1962). 



1 7 



Swinnerton, J. W., Linnenbom, V. J., and Cheek, C. H., 



"Determination of the C-i to C4 Hydrocarbons in Seawater by Gas 



Chromatography", J. Gas Chromatog., 5_, 570 (1967). 



40 



