FAAS Determination of Magnesium, Zinc and Copper in Spinach with Cloud Point Extraction

Trace amount of Mg(Ⅱ), Zn(Ⅱ) and Cu(Ⅱ) were separated and enriched from the sample solution buffered at pH 8.0 in the form of coordination complexes with 8-oxine by cloud point extraction using Triton X-100 as surfactant. An aliquot of the surfactant phase was diluted and made up to 25 mL with methanol and the contents of Mg, Zn and Cu were determined by FAAS. Factors influential to cloud point extraction, and interferences of co-existing ions were studied. Detection limits (3s/k) of the method were found to be 0.057 mg·L-1 for Mg, 0.064 mg·L-1 for Zn and 0.032 mg·L-1 for Cu. The proposed method was applied to the determination of the 3 elements in samples of big-leaf spinach and small-leaf spinach, and values of recovery obtained by standard addition method were found in the ranges of 93.3%-100.5% for Mg, 91.7%-97.9% for Zn, and 94.0%-107.1% for Cu.