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A Simple Device for Collection of Extraction Phase in Dispersive Liquid-Liquid Microextraction Method Based on Solidification of Floating Organic Droplet for Sensitive Determination of Curcumin in Human Serum

A narrow neck glass tube was used for simple and rapid collection of organic phase from the sample surface in dispersive liquid-liquid microextraction method based on solidification of floating organic droplet (DLLME-SFO) after its centrifugation and cooling in a water bath. The method was used for preconcentration and sensitive determination of curcumin in human serum. In the designed method, curcumin was extracted from a mixture of serum and acetone (disperser solvent) into 50 ml 1-dodecanol (organic solvent) after its rapid injection into 4.5 mL of an aqueous medium. Factorial design and central composite design methods were used for optimization of the effects of ionic strength, extraction and disperser solvents’ volumes and pH. Spectrophotometric determinations of the extracts at 419 nm were used during the optimization, but for the serum samples the extracts were injected into an HPLC column for final determinations. In the optimized conditions, quantitative extraction of curcumin from serum samples was achieved with a mean recovery of 95.5 % and an RSD of 8.0 % for six replicates. The calibration curve for the HPLC method was linear up to 4 mg mL−1 with a correlation coefficient of 0.990. Enrichment factors exceeding 25.3 was obtained for curcumin. The detection limit of the method was calculated from 3 s to be as low as 1.2 ng mL−1. The method was applied to the determination of curcumin in several human serum samples with satisfactory results.