Trace determination of lead in lipsticks and hair dyes using microwave-assisted dispersive liquid-liquid microextraction and graphite furnace atomic absorption spectrometry.

Abstract

A novel microwave-assisted dispersive liquid-liquid microextraction (MADLLME) technique according to the solidification of a floating organic droplet (SFO) and graphite furnace atomic absorption spectrometry (GFAAS) used for the extraction and determination of lead ions in lipsticks and hair dyes made in different countries. Lipstick and hair dye samples of different brands and colours were collected from local market in Kermanshah, Iran. After sample treatment with microwave-assisted acid digestion, an appropriate mixture of acetone, 1-undecanol and diethyl dithiophosphoric acid was injected rapidly into the aqueous sample containing lead ions, and as a result, cloudy mixture was formed. After centrifugation, the test tube was cooled for few minutes. The solidified 1-undecanol on top of the solution was transferred into a suitable vial and injected into the analytical instrument. Under the optimum experimental conditions (extraction solvent: 30μL of 1-undecanol; disperser solvent: 500μL of acetone; ligand concentration: 0.15% (v/v); pH: ~1.5 and without salt added), the enhancement factor of 96 was obtained. The calibration graphs were linear in the range of 0.3-50μgkg(-1) with a correlation coefficient (r(2) ) more than 0.995. The detection limit was 0.1μgkg(-1) . Consequently, the developed method was successfully applied to extract and determine lead ions in the lipsticks and hair dyes, and favourable results were obtained. The proposed method which applied in cosmetics showed excellent relative recoveries (90-109.7%) with relative standard deviations <8.3% (n=3) for all samples. The study revealed that the concentration of lead found in lipsticks and hair dyes on the Kermanshah market is far below the recommended limits as applied in Germany (20mg kg(-1) ) and Canada (10mg kg(-1) ) and confirmed that very low levels of lead are technically available in the final cosmetic products.