Chinese Journal of Chromatography ›› 2012, Vol. 30 ›› Issue (04): 374-377.DOI: 10.3724/SP.J.1123.2011.12064

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Direct determination of nitrites, nitrates and phosphates in seawater using suppressed conductivity ion chromatography with large volume injection and on-line sample preparation techniques

LIN Hongmei1,2, LIN Qi1,2*, ZHANG Yuanhui1,2, ZHANG Jingjing3, CHEN Liqi1,2*   

  1. 1. Third Institute of Oceanography, State Oceanic Administration of the People’s Republic of China (SOA), Xiamen 361005, China; 2. Key Laboratory of Global Change and Marine-Atmospheric Chemistry, SOA, Xiamen 361005, China; 3. College of Ocean & Earth Science, Xiamen University, Xiamen 361005, China
  • Received:2011-12-19 Revised:2012-02-27 Online:2012-04-28 Published:2012-04-28

Abstract: Using on-line pre-chlorine and sulfate removal technique, a rapid and direct method was established for the simultaneous determination of nitrite-N, nitrate-N and phosphate-P in seawater by ion chromatography (IC) with suppressed conductivity detection. In this method, an IonPac AG23 column was used as the enrichment column, an IonPac AS23 column with high capacity as the analytical column, and KOH solution as the eluent for gradient elution produced by an eluent generator on-line automatically. The results showed that the determination of the targets was not interfered when a seawater sample diluted 5 to 10 times was directly injected. The method detection limits (MDL) of nitrite-N, nitrate-N and phosphate-P were 0.3, 0.4 and 0.2 μg/L respectively, under the conditions of 500 μL sample volume and 1 mL/min elution rate. The linear ranges of nitrite-N, nitrate-N and phosphate-P were 10~500 μg/L, 14~680 μg/L and 3.4~170 μg/L respectively, and the correlation coefficients (r) were all greater than 0.9990. The average recoveries of the 3 analytes spiked in a sample ranged from 92% to 106% with the relative standard deviations (RSDs, n=6) of 1.2%~7.7%. The whole sample analysis process can be completed in 13 min. The method has the advantage of simple operation, reagent-free and pollution-free, and can meet the quantitative analysis requirements of seawater.

Key words: ion chromatography (IC), large volume injection, nitrates, nitrites, phosphates, seawater, on-line sample preparation technique