Graphene Oxide Nanosheets Modified with 8-Hydroxylquinoline for the Solid Phase Extraction, Preconcentratrion and Flame Atomic Absorption Spectrometric Determination of Copper in Black Tea, Rice and Red Pepper Samples

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A graphene oxide sorbent was modified with 8-hydroxyquinoline and used for solid phase extraction and selective determination of copper using flame atomic absorption spectrometry. In this method, a 5 mg of modified sorbent was added to 50 mL of aqueous solution containing 100 µgL-1 of Cu(II) at pH=3. The sorbent/aqueous solution mixture in the flask was stirred for 30 minutes and then centrifuged. Copper was desorbed from sorbent by 2 mL of 1 mol L-1 HCl, afterwards. The effect of several variables upon extraction efficiency, like: extraction time, pH adjustment and sorbent amount was studied. Under experimental conditions the enrichment factor of 25 was obtained by using of 50 mL of sample solution. The working dynamic range was from 5 to 800 ng mL-1. The limit of detection, limit of quantification and relative standard deviation were 2.16 ng mL-1, 6.51 ng mL-1, and 3 % for eight determinations of 100µg L-1 of Cu(II), respectively. The method was successfully applied for the determination of Cu(II) in black tea, rice and red pepper samples.