The Novel Method of Extraction and Analysis of Melamine in Whole Milk Using Sand Material Cleanup Technique and Inertsil C18 Column by LC-MS/MS

Shalini Sharma; Dr. Rajeshwari Shivaraj; Dr. A. Radhakrishna

Abstract: A simple, precise, accurate and validated Liquid chromatography and Tandem mass spectrometric (LC-MS/MS) method is developed for the analysis of melamine in whole milk. Because of melamine?s basic and polar nature, a cation exchange natural sand material is used as cleanup technique. As a result, enhancement in recovery, sensitivity and selectivity has been observed as well made the analysis much cheaper by replacement of use of cartridge. A simple extraction of melamine with phosphate buffer (in acidic condition) and Acetonitrile (precipitation of the protein), matrix cleanup using silica based strong cationic exchangers (sand) and reconstitution with 0.1% Formic acid (v/v) in Acetonitrile. The separation is performed on a Inertsil ODS-3C18 column (150mm x 4.6mm x 3?m. Two selected reaction monitoring (SRM) transitions are monitored for Melamine. After optimization of instrument parameter and settings, the linear response (r2>0.999) is observed for samples ranging from 0.50 to 10 ?g/kg. The method provides recoveries of 70-120% in the concentration range of 0.50 to 10 ?g/kg, intra- and inter-day variation in <2.5% RSD. The limit of detection (LOD) and limit of quantification (LOQ) values are 0.2 and 0.6 ?g/kg, respectively with an uncertainty of ? 0.03?g/kg at 95 % confidence level.

Keywords: Melamine, Milk, LC-MS/MS, Sand cleanup, Polar.