A new sensitive and simple method was developed for the preconcentration of trace amounts of Ni using 1-(2-pyridylazo)-2-naphthol (PAN) as chelating reagent prior to its determination by ûame atomic absorption spectrometry. The proposed method is based on the uti-lization of a column packed with graphene as sorbent. Several effective parameters on the extraction and complex formation were selected and optimized. Under optimum conditions, the calibration graph was linear in the concentration

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... e concentration range of 5.0-240.0 µg L-1 with a detection limit of 0.36 µg L-1. The relative standard deviation for ten replicate measurements of 20.0 and 100.0 µg L-1 of Ni were 3.45 and 3.18%, respectively. Comparative studies showed that graphene is superior to other adsorbents including C18 silica, graphitic carbon, and single-and multi-walled carbon nanotubes for the extraction of Ni. In the present study, we report the application of preconcentration techniques still continues increasingly for trace metal determinations by flame atomic absorption spectrometry (FAAS) for quantification of Ni in Formalin-fixed paraffin-embedded (FFPE) tissues from Liver loggerhead turtles. The proposed method was successfully applied in the analysis of four real environmental water samples. Good spiked recoveries over the range of 95.8-102.6% were obtained.