中文摘要：

建立了海水中CH3Cl和CH3Br的吹扫-捕集-气相色谱分析方法,确定了最佳实验条件：吹扫时间12min、吹扫气流速50mL/min、吹扫温度40℃、干燥剂Mg（ClO4）2、液氮捕集、沸水解吸2min。本方法对CH3Cl和CH3Br的检出限分别为2.7和0.3pmol/L,相对标准偏差分别1.9%和7.1%,回收率分别为89%～97%和75%～85%。对海水样品保存方法的可靠性和准确性进行了现场研究,结果表明：在24h内样品浓度没有明显变化,在现场调查过程中,一般6h内可测定完毕,因此本方法可以得到准确结果。同时应用本方法对胶州湾表层海水样品中的CH3Cl和CH3Br进行了测定,其浓度范围分别为130～346pmol/L和3.90～20.7pmol/L,和文献报道的其它沿岸水体中的浓度一致,表明本方法能够满足海水中CH3Cl和CH3Br浓度测定的要求。

英文摘要：

The purge-and-trap technique coupled with gas chromatography and electron capture detector（GC-ECD） has been developed for the determination of CH3Cl and CH3Br in seawater. The optimum conditions were established, including purge time（12 min）, purge gas flow rate（50 mL/min）, purge temperature（40 ℃）, desiccant （Mg（ClO4）2）, liquid nitrogen trap, boiling water desorption（2 min）, and gas chromatographic separation and detection. The detection limits were 2.7 and 0.3 pmol/L, the precisions were 2% and 8%, and the recoveries were 89%-97% and 75%-85% for CH3Cl and CH3Br, respectively. Sample storage experiments were carried out to test reliability of the storage procedure used in this study, and the results showed that there was no significant change in the concentrations of CH3Cl and CH3Br in seawater within 24 h. It is believed that exact concentrations can be obtained by this method, because the analysis of CH3Cl and CH3Br are generally completed within 6 h in situ. This method was used to determination in situ CH3Cl and CH3Br concentrations in the surface seawater of Jiaozhou Bay, and the result showed that the CH3Cl and CH3Br concentrations ranged of 130-346 pmol/L and 3.90-20.7 pmol/L, respectively, in good agreement with those reported in literature in other coastal waters. The study shows that this method can satisfy the measurement of in situ CH3Cl and CH3Br concentrations in seawater.