Cyclohexylamine as extraction solvent in extraction and preconcentraion of some heavy metals in aqueous samples based on homogeneous liquid-liquid extraction

Because of the harmful effects of excessive intake of heavy metals ions, it is necessary to determine their concentration in real samples at trace amounts [1]. Homogeneous liquid-liquid extraction (HLLE) is based on the usage of a low dielectric constant organic solvent such as acetonitrile, methanol, acetone, etc., which is soluble in water. An agent is utilized as a phase separation phenomenon in a homogeneous solution to produce two distinct phases [2]. In this method an analyte (organic / inorganic compound) in the homogeneous aqueous solution is extracted in the separated organic phase.A new sample preparation method has been developed for the extraction and preconcentration of some heavy metal cations in aqueous samples using cyclohexylamine-based homogeneous liquid-liquid microextraction. For this purpose, initially to an aqueous solution containing Co (II), Ni (II), and Cu (II)ions in a glass test tube, cyclohexylamine(as a complexing agent) was added at µL level, and a homogeneous solution was formed. After manual shaking, the NaCl was added, and a cloudy solution was formed. The enriched analytes in the upper phase (cyclohexylamine) were determined by graphite furnace atomic absorption spectrometry. Therefore, in the proposed method cyclohexylamine was used as both the complexing agent and the extraction solvent. Several variables possibly affecting the extraction efficiency were investigated and optimized.Under the optimum conditions the calibration curves were linear in the ranges of 80-1000, 40-700, and 80-800 ng L-1 for Co2+, Ni2+, and Cu2+, respectively. Repeatability of the proposed method, expressed as relative standard deviation, ranged from 3.3-5.2% (n=6, C=200ng L-1). Moreover, the detection limits of the selected analytes were obtained in the range of 15.3-37.7 ng L-1. The accuracy of the developed procedure was checked by analyzing NRCC-SLRS4 Riverine water, a certified reference material. Finally, the proposed method has been successfully applied for the simultaneous analysis of the selected analytes in environmental water samples.