1985 Volume 34 Issue 2 Pages 114-118
The trace determination ofn-alkanes in seawater was developed for investigating their background level. Water sample (101) was passed through XAD-2 resin column (1.5cm i.d. × 10cm), after perdeuteratedn-alkanes (C16, C20, C24, and C32) had been added to the sample as internal standards.n-Alkanes adsorbed on the resin were extracted in a Soxhlet extractor with dichloromethane. The extract was concentrated to 1 ml with a Kuderna-Danish evaporator. The concentrate was examined by a gas chromatograph mass spectrometer with a multiple ion detector (GC/MSSID). Precision of the absolute calibration curve method was compared with that of the internal standard method in the temperature programmed chromatography. The relative standard deviation of the absolute calibration curve method and the internal standard method was 9.6% and 4.5%. For recovery test, 1μg of each n-alkane (C13to C32) was added to 5l of 3% sodium chloride solution. n-Alkanes were recovered from the solution by the XAD-2 resin extraction method. Determination was carried out by internal standard method after addition of perdeuterated n-alkanes to the concentrate. The recoveries of low molecular weight n-alkanes (C13to C20) were from 14% to 60% and the those of high molecular weight n-alkanes (C21to C32) more than 70%. One μg of cach n-alkane (C13to C32) and perdeuterated n-alkane (C16, C20, C24, and C32) were added to 5l of water sample and over-all recovery tests of n-alkanes were performed, because the accuracy and the precision of this method were determined. The average recovered amount of n-alkanes was 1.04μg and the average of standard deviations was 0.06μg. n-Alkanes in seawater sample were determined by this method, and the sum of concentrations of n-alkanes (C13to C32) was 2.78ppb.
