| Purge-and-trap with gas chromatography is a kind of fast analysis and easy operation method. It does not need any organic solvent to extract the target compounds in the process of analysis, which resulting in little harm to the analyst and environment and less pollution to column. Moreover, chromatogram spectroscopies have high resolution. The method is in line with the "green analytical chemistry" requirement, and therefore is widely used in environmental monitoring, traditional Chinese Medicine composition analysis, food and health quarantine, pharmacokinetic and organic solvent residues detection, etc.A purge-and-trap combined with gas chromatography analysis method was established for simultaneous determination of 8 kinds of benzene and 5 kinds of volatile halohydrocarbons in surface water and industrial waste water in this paper. The sample collection and preservation, purge time, desorption temperature and time, the selection of chromatography column, chromatographic conditions were studied and optimized to obtain the optimal conditions.In order to measure 8 kinds of benzene in surface water and industrial wastewater, the gas chromatography was equipped with a CP-WAX52CB chromatographic column (30 m × 0.25 mm × 0.25μm) and a hydrogen flame ionization detector (FID). Injector temperature was 220 ℃ and detector temperature was 250 ℃. High purity N2 (99.999%) was used as carrier gas, and the flow rate was 1.0 mL/min. The flow rate of H2 and air used in FID was 30 mL/min and 300 mL/min, respectively. The flow rate of make-up gas was 30 mL/min and the split ratio was 20:1. The oven was set at 40℃ (5 min) and raised to 140℃ at 10℃/min and the final temperature was maintained for 3 min and the total run time was of 18 min.The chromatographic conditions for 5 kinds of halogenated hydrocarbon in the surface water and industrial wastewater were as following:CP-Si18CB chromatographic colμmn (30 m × 0.25 mm × 0.25 μm) and electron capture detector (ECD) were equipped in the gas chromatograph, the injector temperature and detector temperature were 220℃ and 250℃, respectively. The flow rate of high purity N2 (99.999%) used as carrier gas was 1.0 mL/min. The split ratio was 20:1 and the flow rate of make-up gas was 30 mL/min. The oven temperature was set as mentioned above.Purge and trap conditions:Capture Trap-10 was applied in this study. The purging pipe saddle was set at 50℃. Purging time and dry purge time were 11 min and 3 min, respectively. Heat temperature was 240℃ and heat time was 8 min. desorption time was 2 min and desorption temperature was 190℃. The flow rate of high purity N2 (99.999%) was 40 mL/min. Analysis sample volμme was 5 ml. each sample after purging cleaning step at a time. There was a cleaning step after each sweeping.The results showed that the relative standard deviations of 0.54-2.27%, recoveries of 90.0～106% and the lowest detection limits of 0.4μg/L～0.8μg/L for 8 kinds of benzene were obtained. In addition, for 5 kinds of halogenated hydrocarbon, the relative standard deviations, recoveries and the lowest detection limits were in the range of 1.46%-4.85%, 92.0%～104% and 0.01μg/L～0.05μg/L, respectively. This method can effectively shorten the analysis time, reduce the usage of organic solvents, and improve the sensitivity and accuracy of the method, which is suitable for determination of benzene and volatile halogenated hydrocarbons in water. |
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