Determination of trace iodide in seawater by capillary electrophoresis following transient isotachophoretic preconcentration comparison with io chromatography

摘要

Usefulness of caplillary electrophoresis (CE)in combination with transient isotachophoresis(tITP)as on-line preconcentratin technique was exmined for routine analysis of trace iodide in seawater.The combined method was based on an electrolyte system where 0.5 moll~-1 sodium chloride and 25 mmol l~-1 cetyltrimethylammonium chloride at an acidic pH AND 0.5mol l~-1 2-(N-morpholine)ethanesulfonate (pH 6.0)served as carrier and terminating electrolyte,respecively.Under optimized tITP-CE conditions (a carrier electrolyte pH OF 2.4),the peak of 1mug l~-1 iodide in artifical seawater can be clearly detected at 226 jnm,with the detectin limit as low as 0.2 mug l~-1.Calibratin curve was linear in the range of 0-40 mug l~-1 (n=10;regressin coefficient=0.99992).Relative standard deviation values of the migratin time,peak heitht and area of surface seawater iodide (0.6 3.1 and 1.5%,respectively)proved an excellent run-to-run reprdoucibility performance of the proposed method.The method was applied to seawater samples containing sub- and low-mug l~-1 levels of iodide,and the results obtained agreed well with ion chromatographic data.Detectin of nitrate and nitrite was also possible in the same tITP-CE run(limits of detection 25 and 20mug l~-1),respectively,at 210 nm).The analytical characteristics of the method were discussed in comparison with an ion chromatographic procedure previously developed in authors'laboratory.