Study On Determination Of Trace Elements In Environmental Samples By Inductively Coupled Plasma-Atomic Emission Spectrometry After Dual Cloud Point Extraction

A novel dual cloud point extraction (dCPE) was developed recently which has played important roles in the field of life science and environmental science. A procedure for dCPE was based on conventional method called cloud point extraction (CPE). Back-extraction reagent was added after the first CPE, then the system underwent heating and centrifugation, and analytes were also seperated from hydrophobic phase to hydrophilic phase. At last, analytes were analyzed by modern chemical instruments. The two phases were separated, which resulted from the effect of experimental conditions such as pH, ionic strength and temperature, etc. dCPE is an easy, safe, high efficiency and inexpensive methodology for separation and preconcentration. The dCPE technique has been applied in the chemical substances, such as phenols, auxin, and mercury classes, and also combined with capillary electrophoresis. However, based on dCPE-ICP-AES in trace anaiysis has seldom been reported. A new method for the determination of trace elements in environmental water was proposed in this paper. Firstly, trace elements in environmental water were preconcentrated though dCPE mentioned above; secondly, preconcentrated elements were detected by ICP-AES simultaneously. Satisfaction results were obtained, such as high sensitivity, veracity, and low limits of detection (LOD).This present experiment consists of two parts as follow:1. 1-(2-pyridylazo)-2-naphthol was used as chelating reagent, TritonX-114 as surfactant and HNO3 as back-extraction reagent for the dCPE of Cd, Ni, Pb, Zn, Cu and Mn. Then the effect of experimental conditions was optimized, such as pH, back-extration reagent concentration, buffer solution dosage, PAN concentration, TritonX-114 concentration, equilibration temperature and time, centrifugation time, ion strength and interference ions, etc. Under the optimum conditions, dCPE in the presence of pH 10,2 mL back-extraction reagent HNO3 concentration 2 mol L-1, PAN concentration 1.96×10-5 mol L-1, TritonX-114 concentration 0.1%permitted the preconcentrated factors of 17.88,20.66,24.24,16.79,19.33 and 19.97, and the detection of 0.0004,0.0016,0.0079,0.0018,0.0015 and 0.0013μg mL-1 for Cd, Ni, Pb, Zn, Cu and Mn, respectively. All the elements'R2 were more than 0.9494. The proposed method was applied to the determination in water sample, such as tap water, river and lake with satisfactory results.2. Cd, Ni, Zn, Cu and Fe reacted with DDTC followed by the first experiment idea and procedure, and then optimize all the conditions, too. At last, in the presence of pH 10,2 mL back-extraction reagent HNO3 concentration 2 mol L-1, DDTC concentration 5×10-4 g mL-1, TritonX-114 concentration 0.1%permitted the preconcentrated factors of 17.72,18.33,15.96,18.95 and 16.58, and the detection of 0.0001,0.0004,0.0005,0.0024 and 0.0021μg mL-1 for Cd, Ni, Zn, Cu and Fe, respectively. All the elements'R2 were more than 0.9915. The proposed method was applied to the determination in water sample, such as tap water, river and lake with satisfactory results.