海水中除含有钠、镁、钙、钾、锶、硼、氯化物、硫酸盐、溴化物、碳酸盐及氟化物等十一种含量在1 ppm 以上的常量元素外,还含有数十种含量在1 ppm 以下的微量元素。这些微量元素的含量常随空间、时间而有所差异,它们的含量常以 ppb(10~(-9))计算,有些元素的含量甚至低至 ppt(10~(-12))量级。由于海水中微量元素的含量低,某些分析方法的灵敏度受到了限制,不适于这些元素的测定。而可用以测定海水中微量元素的分析方法有:中子活化法,放射化学分析法,原子吸收分光光度法,分光光度法,火焰光度法,萤光分析法,X 射线萤光 In addition to the seawater containing 11 elements such as sodium, magnesium, calcium, potassium, strontium, boron, chloride, sulfate, bromide, carbonate and fluoride content of 1 ppm or more of the elements, but also contains dozens of Trace elements below 1 ppm. The content of these trace elements often varies with space and time, and their content is often calculated as ppb (10-9), with some elements even down to the order of ppt (10-12). Due to the low content of trace elements in seawater, the sensitivity of some analytical methods is limited and not suitable for the determination of these elements. Analytical methods that can be used to determine trace elements in seawater include neutron activation, radiochemical analysis, atomic absorption spectrophotometry, spectrophotometry, flame photometry, fluorescence analysis, X-ray fluorescence