Abstract

A novel, simple, sensitive and effective method has been developed for preconcentration of Ni (II) on functionalized Graphene oxide with covalently linked porphyrin (GO–H₂NP) solid-phase extraction adsorbent. The stability of a chemical (GO–H₂NP), especially in concentrated hydrochloric acid, was then used as a recycling and pre-concentration reagent. The method is based on selective chelation of Ni(II) on surfactant coated C₁₈, modified with functionalized GO with covalently linked porphyrin (GO–H₂NP). The retained ions were then eluted with 4 ml of 4 M nitric acid and determined by flame atomic absorption spectrometry (FAAS) at 283.3 nm for Ni. The influence of flow rates of sample and eluent solutions, pH, breakthrough volume, effect of foreign ions on chelation and recovery were investigated. 1.5 g of surfactant coated C₁₈ adsorbs 40 mg of the functionalized Graphene oxide with covalently linked porphyrin (GO–H₂NP) base which in turn can retain 20.0 ± 0.9 mg of each of the two ions. The limit of detection (3σ) for Ni (II) was found to be 5.40 ngL^-1. The enrichment factor for both ions is 100. The mentioned method was successfully applied on the determination of Ni in different water samples. The ions were also speciated by means of a three columns system.

Key words: Determination of Ni, pre-concentration, functionalized graphene oxide, covalently linked porphyrin (GO–H₂NP), flame atomic absorption spectrometry (FAAS).