Extraction of Cu, Fe, Mn, and Ni from Margarine Samples Using Extraction Induced by Emulsion Breaking Procedure Prior to Graphite Furnace Atomic Absorption Spectrometry and Comparison of Results to Provisional Tolerable Daily Intake Values

BACKGROUNDThe emulsion induced by emulsion breaking (EIEB) procedure was previously reported for the extraction of copper, iron, manganese, and nickel from liquid oil samples such as vegetable oil. OBJECTIVETo optimize the EIEB procedure for determination of copper, iron, manganese, and nickel in solid oil (margarine) samples by Graphite Furnace Atomic Absorption Spectrometry (GFAAS). METHODSThe extraction procedure uses a surfactant in nitric acid to form an emulsion followed by heating to break the emulsion. Optimization included variation of the test portion size, the type and concentration of the surfactant, the concentration of nitric acid in the aqueous solution, the emulsion agitation time, heating temperature, and the time required to break the emulsion. RESULTSMean element concentrations of 11 margarine samples were in the following ranges: Cu 0.031-0.131 µg/g, Fe 5.7-24.9 µg/g, Mn 0.542-1.11 µg/g, and Ni 0.108-0.134 µg/g. Under the optimized extraction conditions, the detection limits (µg/kg) were 4.8, 13, 1.5, and 23 for Cu, Fe, Mn, and Ni, respectively. The accuracy of the extraction procedure was determined by comparison to commonly used microwave digestion procedure. The EIEB results were not statistically different from the microwave digestion results when analyzed by GFAAS as determined by the statistical tests. CONCLUSIONSThe EIEB procedure was shown to be equivalent to the commonly used microwave digestion procedure for extraction of analytes from margarine samples. HIGHLIGHTSThe optimized EIEB extraction procedure is simple, rapid, low cost, and environmentally friendly. It has improved detection limits and allows calibration with aqueous standards.