Application Of A Novel Liquid–phase Microextraction Based On Solidification Of Floating Organic Droplet Method For The Analysis Of Trace Metal Elements

Sample preparation is one of the most important and crucial steps in the whole analytical process to obtain accurate and sensitive results. The objective of the sample preparation is not only to isolate the target analytes from the samples, thus reducing or even eliminating the interferences originally present in the sample, but also to concentrate the analytes to facilitate their determinations at low levels. Recently, much attention is being paid to the development of miniaturized, more efficient, and environmentally friendly extraction techniques which could greatly reduce the organic solvent consumptions. For this purpose, the liquid-phase microextraction (LPME) procedure, which is based on the distribution of the analytes between a microvolume of organic solvent and the aqueous solution, has emerged as an attractive alternative for the sample preparation because of its simplicity, effectiveness, low cost, minimum use of organic solvents.The recent developments and different types of liquid-phase microextraction for the determination of metal elements are summarized in the first part. A detailed review concerning the procedure and theory of a novel LPME technique was also presented.In the work, two analytical methods were developed for the determination of trace metal elements in environmental water samples by ultrasound-assisted solidified floating organic drop microextraction ( USA-SFODME ) and dispersive liquid–liquid microextraction based on solidification of ?oating organic droplet(DLLME-SFO)coupled with flame atomic absorption spectrometry (FAAS). This dissertation is mainly concerned with the following aspects:(1) A novel method for the extraction and preconcentration of trace copper, zinc, cadmium from water samples by USA-SFODME coupled with FAAS was developed. In the proposed approach, PAN was used as chelating agent and 1-dodecanol was selected as extraction solvent. Some effective parameters on the microextraction and the complex formation were selected and optimized. These parameters included extraction solvent type, pH, the amount of the chelating agent, extraction time and extraction temperature. Under the optimum conditions, enrichment factors of up to 115、76 and 81 were achieved for Cu、 Zn and Cd, respectively. The calibration graphs were linear in the range of 20~600μg/L, 20~450μg/L and 10~450μg/L with detection limits of 0.76μg/L, 0.79μg/L, 0.66μg/L for Cu、Zn and Cd, respectively. The relative standard deviations varied from 2.42% to 4.02% (n=10). The method was applied to the analysis of tap, river, and sea water samples and good spiked recoveries over the range of 90.5～101.5% were obtained.(2) A novel method for the extraction and preconcentration of trace cobalt, nickel, lead from water samples by DLLME-SFO coupled with FAAS was developed. In the proposed approach, APDC was used as chelating agent and 1-dodecanol was selected as extraction solvent. Some effective parameters on the microextraction and the complex formation were selected and optimized. These parameters included the type of extraction and dispersive solvents, pH, the amount of the chelating agent, extraction time and salt addition. Under the optimum conditions, enrichment factors of up to 160, 158 and 151 were achieved for Co、Ni and Pb, respectively. The calibration graphs were linear in the range of 1.15~110μg/L、4.23~250μg/L and 18.43~400μg/L with detection limits of 0.35μg/L、1.27μg/L、2.53μg/L for Co、Ni and Pb, respectively. The relative standard deviations varied from 2.55% to 3.41% (n=10). The method was applied to the analysis of tap, river, and sea water samples and good spiked recoveries over the range of 94.5%~100.7% were obtained.