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在测定溶液中低含量化学成份时,虽然有许多化学方法可用,但吸光光度法由于仪器设计的进步与更灵敏、选择性更好的显色剂的发明,使用最广泛。不过,直接用分光光度法测定天然水中痕量元素仍有困难,有时须用诸如溶剂萃取、离子交换之类的预富集手段。在溶剂萃取法中,想用高的相间体积比来使痕量组份有效地富集难以奏效,困难在于相的分离与相间的溶解。离子交换法常较适用,但吸着在离子交换树脂上的化学
Although many chemistries are available for the determination of low levels of chemical constituents in solution, the most widely used spectrophotometric method is due to the advances in instrumentation and the invention of more sensitive and selective developers. However, direct spectrophotometric determination of trace elements in natural water is still difficult and sometimes requires preconcentration such as solvent extraction and ion exchange. In the solvent extraction method, it is difficult to effectively enrich the trace components by using the high phase-to-volume ratio. The difficulty lies in the phase separation and the interphase dissolution. Ion exchange method is often applicable, but sorbed on the ion exchange resin chemistry