Sensitive determination of melamine in milk and powdered infant formula samples by high-performance liquid chromatography using dabsyl chloride derivatization followed by dispersive liquid-liquid microextraction.

A new and sensitive pre-column derivatization with dabsyl chloride followed by dispersive liquid-liquid microextraction was developed for the analysis of melamine (MEL) in raw milk and powdered infant formula samples by high performance liquid chromatography (HPLC) with visible detection. Derivatization with dabsyl chloride leads to improving sensitivity and hydrophobicity of MEL. Under optimum conditions of derivatization and microextraction steps, the method yielded a linear calibration curve ranging from 1.0 to 500μgL with a determination coefficient (R) of 0.9995. Limit of detection and limit of quantification were 0.1 and 0.3μgL, respectively. The relative standard deviation (RSD%) for intra-day (repeatability) and inter-day (reproducibility) at 25 and 100μgL levels of MEL was less than 7.0% (n=6). Finally, the proposed method was successfully applied for the preconcentration and determination of MEL in different raw milk and powdered infant formula, and satisfactory results were obtained (relative recovery ⩾94%).