Two New Separation And Enrichment Method In The Application Of Spectral Analysis

As a modern instrumental analysis method, the spectral analysis has been extensively applied in the metallurgy, geology, medicine, agriculture, environmental protection and other fields, due to the advantages of high sensitivity and rapid determination. Although the modern spectrum instruments have high sensitvity and detectablity, direct deterimation of trace analyte in complicated samples becomes an impossible task. Because the sample matrix is very complicated and the analyte is always at low concentration level with the development of complex and diversified analytical objects. Therefore, to improve the sensitivity and selectivity of method, different sample pre-treatment techniques would be essentially involved for the separation and/or preconcentration of trace target analyte from the complex matrix prior to determination. In this paper, two methods basing on solidified floating organic drop microextraction and magnetic mixed hemimicelles solid phase extraction were mainly studied on the application of spectrum analysis. The major contents are described as follows:Part1. Solidified floating organic drop microextraction coupled with ultrasound-assisted back-extraction for determination of Se(IV) by hydride generation atomic fluorescence spectrometryA method for the determination of trace amounts of Se(IV) by solidified floating organic drop microextraction (SFODME) coupled with ultrasound-assisted back-extraction and hydride generation atomic fluorescence spectrometry (HG-AFS) is successfully proposed. The method is based on the introduction of solidification of a floating organic drop by using1-undecanol to extract the target analytes after chelate formation with the water soluble ligand and followed by ultrasound-assisted back-extraction into a aqueous solution. The subsequent hydride generation procedure was obtained by merging the sample and NaBH4solutions and detected with atomic fluorescence spectrometry. Under the optimum experimental conditions, a linear calibration curve within the range of0.01-5.0μg/L and detection limit of7ng/L were obtained. With a sample consumption of10mL, a good relative standard deviation of2.1%at1.0μg/L and an enrichment factor of15were achieved. The procedure was applied to tap water, lake water, and accuracy was assessed through the analysis of certified reference materials.Part2. Rapid simultaneous analysis of1-naphthol and2-naphthol in water samples by solidified floating organic drop microextraction coupled with first derivative synchronous fluorescence spectrometryA novel method of solidified floating organic drop microextraction coupled with first derivative synchronous fluorescence spectrometry was developed for the rapid simultaneous analysis of trace1-naphthol and2-naphthol in water samples.1-Naphthol and2-naphthol were firstly perconcentrated by solidified floating organic drop microextraction, and then detected simultaneously by first derivative synchronous fluorescence spectrometry using zero crossing method. In the optimal experimental conditions, there was a linear relationship between the fluorescence intensity and the concentration of1-naphthol and2-naphthol in the range of2to500μg/L,1to600μg/L, respectively. The limits of detection (LOD) for1-naphthol and2-naphthol were found to be0.56μg/L and0.43μg/L. The enrichment factor of1-naphthol and2-naphthol were18and22, respectively when the sample consumption was10mL. The proposed method is reliable, selective and sensitive, and has been used successfully in the determination of traces of1-naphthol and2-naphthol in synthetic mixtures and environmental water samples.Part3. Analysis of trace cobalt in water samples based on magnetic mixed hemimicelles solid phase extraction in sequential injection system coupled with electrothermal atomic absorption spectrometry detectionA new approach for the determination of trace cobalt in water samples employing magnetic mixed hemimicelles solid phase extraction in sequential injection system with detection by electrothermal atomic absorption spectrometry is presented. A novel type of Alumina-coated iron oxide magnetite nanoparticle modified by surfactants has been successfully synthesized and was applied as an effective sorbent material for the pre-concentration of cobalt. The particles were trapped and concentrated inside the microcolumn using a simple strong permanent magnet. The method eliminates the need to use any obstacles to immobilize the sorbent. Extraction, elution, and detection of the analyte were performed sequentially in the sequential injection system. This on-line extraction technique would enable rapid analysis, the low sample and reagents consumption as well as simple sample handling. Under the optimal conditions, the calibration curve showed an excellent linearity in the concentration range of0.01-5.0ug/L along with a detection limit of6ng/L.The relative standard deviation was2.8%at the0.5μg/L level (n=11). An enrichment factor of30and a sampling frequency of18/h were achieved with a sample consumption of2mL. The present method has been successfully applied to cobalt determination in two certified reference materials and water samples.