测定海水中三甲胺含量的现有方法存在样品用量大、仪器昂贵或操作繁琐等问题，因此进行了题示研究。取10.00 mL海水样品置于20 mL顶空瓶中，加入2.5 g氯化钠、0.8 g硫酸钾和2.5 mL 7.5 mol·L^-1氢氧化钠溶液，于85℃平衡40 min，所得气体进入气相色谱仪，在CP-Volamine石英毛细管色谱柱上用升温程序分离，用氮磷检测器测定三甲胺的含量，基质匹配法定量。结果显示，三甲胺的质量浓度在5.0~100.0 μg·L^-1内和其对应的响应信号呈线性关系，检出限（3.143s）为0.4 μg·L^-1。方法用于加标空白样品的分析，测定值的相对标准偏差（n=5）为2.1%，回收率为92.0%~118%。

The existing methods for the determination of trimethylamine in seawater had problems such as large sample amount, expensive instrument, or cumbersome operations, so the research mentioned by the title was conducted. An aliquot (10.00 mL) of seawater sample was taken and placed into a 20 mL-headspace bottle, 2.5 g of sodium chloride, 0.8 g of potassium sulfate, and 2.5 mL of 7.5 mol·L^-1 sodium hydroxide solution were added. The mixture was equilibrated at 85℃ for 40 min. The obtained gas was introduced into the gas chromatograph, and the separation was conducted by heating program on the CP-Volamine quartz capillary column, and trimethylamine was determined by the nitrogen phosphorus detector, with the matrix matching method for quantification. It was shown that linear relationship between values of the mass concentration of trimethylamine and the response signal was kept in the range of 5.0-100.0 μg·L^-1, with detection limit (3.143s) of 0.4 μg·L^-1.The proposed method was applied to the analysis of the spiked blank sample, RSDs (n=5) of the determined values was 2.1%, and recoveries ranged from 92.0% to 118%.