An electrodialytic device for automated inorganic anion preconcentration with determination by ion...

A 4-layer sandwiched device (4LSD) well suited for coupling to online ion chromatography (IC) systems was described and simultaneously performed target anion enrichment, matrix removal and sample injection within seconds. The basic assembly consisted of an extraction solution channel, a sample solution channel and two electrolyte channels. Cation-exchange resin (CER) was utilized to support the solution chamber, increase electrical conductivity and improve pressure resistance to achieve compatibility with a peristaltic pump. Filter placement ensured loop circulation of the 4LSD and prevented resin leakage. The 4LSD showed comparable performance to that of conventional solid-phase extraction (SPE) pretreatment in terms of matrix interference removal while enabling automation. The applied current, sample/extraction solution flow rate ratio, and initial concentration were discussed and optimized. Controllable 1-40-fold enrichment can be ensured. The migration phenomenon of different anions was discussed. F^-, Cl^-, NO₂^-, Br^-, NO₃^-, SO₄^2- and ClO₄^- exhibited satisfactory linear detection ranges within 2.5-1000 μg·L^-1, and the calculated limits of detection (LODs) in milk formula were within the 0.097-0.79 mg·kg^-1 range. The 4LSD was successfully applied to the determination of anions in milk formula with good spiked recoveries ranging between 92.54% and 107.2%, except for the NO₂^- recovery. The relative standard deviations (RSDs) ranged from 0.69% to 8.29%.