Octadecyl-bonded silica membrane disk modified with Cyanex302 for pre-concentration and determination of iron in food products.

A simple and rapid method using an octadecyl-bonded silica membrane disk impregnated with Cyanex302 is described for the pre-concentration and determination of iron. The influence of various parameters on sorption and elution of Fe(III) were systematically investigated. The sorption of Fe(III) at pH 3.2 was quantitative (99.3 +/- 1.1%). It was completely recovered using 20 mL 5.0 M HCI and determined by flame atomic absorption spectrometry. Breakthrough volume of the modified disk for Fe(III) was >2000 mL, pre-concentration factor was >100, and reusability up to 28 cycles. The LOD and LOQ for Fe(III) were 0.45 microg/L and 1.51 microg/L, respectively, while precision for its determination in terms of RSD was < or =2.1%. This method was applied for Fe(III) determination in milk, fortified flour, cocoa powder, tea, and black pepper. To validate the procedure, EPA Method Standard (QC standard 21) was analyzed for Fe(III).