Determination of arsenic and mercury in sunflower oil by electrothermal atomic absorption

A simple and fast method for the determination of arsenic (As) in sunflower oil by electrothermal atomic absorption (ETAAS) is described. The optimal instrumental parameters for ETAAS measurement of As species in stable and homogeneous soap emulsions prepared from oil samples with tetramethylammonium hydroxide (TMAH) have been established. The limit of determination is 5 ng g(-1) total As in sunflower oil. A second approach involving extraction of As and mercury from sunflower oil and consequent ETAAS measurement is also described. Simultaneous quantitative extraction of As(III), As( V), monomethylarsonate (MMA) and dimethylarsinate (DMA) as well as Hg(II), monomethylmercury(II) chloride (MMC), dimethylmercury (DMM), diethylmercury (DEM) and diphenylmercury (DPM) is achieved by using an extraction mixture comprising of 0.1 m NH3/0.01 m EDTA. Pre-reduced palladium is applied as an effective modifier for the next ETAAS measurement of all extracted species. The method of standard addition is employed for calibration. The accuracy and reproducibly of the methods was established by spike and recovery experiments and parallel analysis of sunflower oils from the marketplace. Limits of determination of 2 ng g(-1) for As and 3 ng g(-1) for mercury were obtained.