Determination Of Trace Metal Ions By Cloud Point Extraction-Flame Atomic Absorption Spectrometry

With the development of science and technology, analytical methods are required for the determination of trace elements in geological, biological and environmental samples. Flame atomic absorption spectrometry (FAAS) has been widely used for the determination of trace metal ions because of the relatively simple and inexpensive equipment required. However, direct determination of metal ions at trace levels by FAAS is limited not only due to insufficient sensitivity, but also to matrix interference. Under these circumstances, in order to determine trace levels of metal ions, a separation and enrichment step prior to their determinations may be beneficial.Cloud point extraction(CPE) is a new liquid-liquid extraction which is based on the solubility and cloud point phenomenon of aqueous solution of surfactants, upon alteration of the experimental conditions such as pH value solution, ionic strength, temperature, and the solution is separated into phases, which results in the separation of hydrophobe and hydrophile. CPE is an easy, safe, high efficiency and inexpensive methodology for separation and preconcentration. It has been widely used in the study of life sciences and environment sciences, and has also been successfully used in the separation and preconcentration of metal element.A new method for the determination of trace metal ions by flame atomic absorption spectrometry with cloud point extraction was developed. This method is based on employing Triton X-114 as nonionic surfactant, Ammonium pyrrolidine dithiocarbamate (APDC), 1-(2-pyridylazo)-2-naphthol(PAN) and sodium diethyldithiocarbamate(DDTC) as complexing reagent. The effect of experimental conditions such as pH and concentration of reagents on cloud point extraction was optimized in the following three systems.(1) A new method for the determination of Cd2+ by flame atomic absorption spectrometry with cloud point extraction was developed. In APDC-Triton X-114 system, under the optimum conditions, the detection limit of Cd2+ was 0.311μg/L. The method has been applied to the determination of Cd2+ in samples with satisfactory recoveries ranging from 95.3% to 102.0 %. (2) A new method for the determination of Zn2+ by flame atomic absorption spectrometry with cloud point extraction was developed. In PAN-Triton X-114 system, under the optimum conditions, the detection limit of Zn2+ was 0.687μg/L. The method has been applied to the determination of Zn2+ in samples with satisfactory recoveries ranging from 95.0 % to 102.0 %.(3) A new method for the determination of Co2+, Ni2+ and Cu2+ by flame atomic absorption spectrometry with cloud point extraction was developed. In DDTC- Triton X-114 system, the detection limit of Co2+, Ni2+ and Cu2+ was 0.288μg/L, 0.781μg/L, 0.179μg/L. The method has been applied to the determination of Co2+,Ni2+ and Cu2+ in samples with satisfactory recoveries ranging from 95.5% to 103.2%.