[Determination of inorganic anions and gluconate by two-dimensional ion chromatography]

A new two-dimensional ion chromatography method was developed to parallelly analyze two different types of samples with the application of valve switching technology-suppressed conductivity and pulsed amperometric analysis system, for concurrent determination of chloride, nitrite, sulfate, nitrate four inorganic anions and gluconate. The first dimensional chromatography was using Ionpac AG18+Ionpac AS18 anion analysis columns with a suppressed conductivity detector for the separation and detection of Cl-, NO2-, SO4(2-) and NO3-. Respectively, the elution was 5 and 20 mmol/L NaOH at an isocratic flow rate of 1.0 mL/min and sample injection volume of 25 μL. The second dimensional chromatography was utilizing two guard columns, CarboPac PA1 and CarboPac PA20, with 90 mmol/L NaOH solution for the isocratic eluent of 0.8 mL/min. Gluconate was enriched by an AG15 column and switched into the pulsed amperometric detector. The results showed that: each inorganic anion in 0. 1-5.0 mg/L and gluconate in 0.085 6-4.282 5 mg/L had a good linear relationship (R2 ≥ 0.994 5). The RSDs of the peak areas were between 1.05%-1.94%. The limits of detection were 0.61-2.17 μg/L for the anions and 24.24 μg/L for the gluconate. The recoveries were between 90.3% - 102.8%. The two detection modes parallelly have good separation efficiency, detection accuracy and the precision of the separation and are suitable for the analysis of complex samples.