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Carbon paste electrodes were modified by mixing appropriate amounts of the monomers o-phenylendiamine, pphenylendiamine and m-phenylendiamine (o-PD, p-PD and m-PD) into a graphite powder-paraffin oil matrix. The electropolymerization of the incorporated phenylendiamine was then carried out in a carbon paste electrode in acidic medium by cyclic voltammetry between À 0.30 V and þ 0.90 or under constant potential. The modified carbon paste electrodes (MCPEs) obtained by this electropolymerization method were found to be useful for trace determination of Pb 2þ in aqueous solutions. Lead(II) was first preconcentrated on the modified electrodes by complexation with the modifier, and the electrode was then transferred to an electrochemical cell. The best results in terms of sensitivity and detection limit were obtained with poly p-phenylenediamine (poly (p-PD)). For a 10-min preconcentration time, the calibration plot was linear from 5 Â 10, with r 2 ¼ 0.999 and relative standard deviation equal to 5%. However, the lowest lead concentration that could be detected was 10 À9 mol L À1 . Interference from metal ions like Cd(II), Hg(II), Zn(II), Fe(II) and Cu(II) was also studied.

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This study aimed to determine the total arsenic concentration in lipsticks and evaluate the potential health risks due to daily ingestion of this toxic element from this product. The samples were analyzed using atomic fluorescence spectrometry technique after mineralization and hydride generation (HG-AFS). The calibration curve is linear over a concentration range from 0.125 to 2 µg L-1 with a regression coefficient of the order of 0.9899. The limit of detection is reaches 3 ng g-1. The standard deviation is of the order of 4%.The accuracy of this method was evaluated by calculating the recoveries of additions of arsenic to three lipstick samples. These results indicate recovery rates between 91% and 98%. Finely, the results found demonstrate that the method used in this work is suitable for arsenic detection in lipsticks samples.