Determination of low levels of molybdenum (VI) in food samples and beverages by cloud point extraction coupled with flame atomic absorption spectrometry

Cloud point extraction (CPE) was used for the preconcentration of molybdenum (Mo), after the formation of a complex with Victoria pure blue BO (VPB+) in presence of excess thiocyanate and cetylpyridinium chloride (CPC) at pH 2.0, and further determination by flame atomic absorption spectrometry (FAAS) using Triton X-114 as surfactant. The main factors affecting the CPE, such as concentration of thiocyanate, VPB+, CPC, Triton X-114, pH, equilibration temperature and incubation time, were optimized for the best extract efficiency. Under the optimized conditions, a 32-fold enhancement factor was reached. The lower limit of detection (LOD) obtained under the optimal conditions was 2.18 μg L−1. The accuracy (REs) and precision (RSDs) for five replicate determinations at 250 μg L−1 Mo were 3.25 and 2.36% after preconcentration with CPE. The calibration graph using the preconcentration method was highly linear with a correlation coefficient of 0.9949 in range of 7.5–1800 μg L−1. The method was successfully applied to the determination of Mo in beverages and food samples and in certified reference materials. The results of developed method were compared with those of independent ICP-OES method, and quantitatively verified and validated with recoveries.