A new potassium tetrabromoaurate (III)-luminol chemiluminescence system for the determination of folic acid in milk powder.

UNLABELLED: A new chemiluminescence (CL) system based on the CL-emitting reaction between potassium tetrabromoaurate (III) [Au(III)] and luminol in alkaline medium is described in this paper. On the basis of this study, folic acid (FA) could dramatically enhance CL intensities, and incorporated with flow injection (FI) and solid-phase extraction (SPE), the novel CL system has been applied for the determination of FA in infant formula milk powder. Under optimum conditions, the CL intensities were linearly related to the concentration of FA in the range of 8.0 × 10⁻⁸ to 4.0 × 10⁻⁵ g/L with a correlation coefficient of 0.999, and the detection limit was 2.0 × 10⁻⁸ g/L. The relative standard deviation was 3.5% for 1.0 × 10⁻⁶ g/L FA. The optimal conditions for the detection of FA were evaluated, and the interferences from some common inorganic ions and a couple of relevant organic compounds were also investigated. PRACTICAL APPLICATION: The new Au(III)-luminol chemiluminescent system is proposed for the determination of FA; it will be an adequate technique for the analysis of low FA concentrations in pharmaceutical preparations and food samples, and it will have potential analytical applications for other substances.