An automated catalytic spectrophotometric method for manganese analysis using a chip-multisyringe flow injection system (Chip-MSFIA)

Abstract

In this work, we present an automated catalytic spectrophotometric method for determination of Mn(II) by using a multisyringe burette coupled to a chip microfluidic-conductor (Chip-MSFIA). The reaction is based on the catalytic effect of Mn(II) on the auto-oxidation reaction of succinimidedioxime (SIDO). Reagents and the sample were simultaneously dispensed to the chip for their complete mixing, heating, and measurement. The absorbance of the reaction product was measured at 700 nm. The product concentration could be determined by the fixed-time and the initial rate method under optimum conditions (temperature 35 °C, 4.70 mmol L⁻¹ SIDO, and 0.60 mol L⁻¹ NaOH). Both fixed-time and initial rate methods have been developed, with the fixed-time method giving higher reproducibility and a wider working range. Therefore it was selected for Mn(II) samples in the working range of 1–20 μg L⁻¹ of Mn(II). The estimated precision was 0.67% (5 μg L⁻¹, n = 15) and the limit of detection of Mn(II) was 0.33 μg L⁻¹. The proposed method is highly sensitive, selective, and simple for trace Mn(II) determination without extraction and separation steps. The system was successfully applied to water samples with an injection throughput of 22 injections h⁻¹.