Abstract:

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 0.0856-4.2825 mg/L had a good linear relationship (R²≥0.9945). 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.

Key words: conductivity, gluconate, inorganic anion, pulsed amperometric, two-dimensional ion chromatography