Cloud Point Extraction-spectrophotometric Determination Of Malachite Green And Other Hazardous Substances In Environmental Water Samples Using Partial Least Squares Methods

Cloud point extraction (CPE) is a kind of new environmentally benign liquid-liquid microextraction method. This technique is based on the properties that most non-ionic suarfctants in aqueous solutions can form micelles and become tubrid when heated to a temperuatre known as the cloud point temperature. Above the cloud point,the micellar solution separates into a suarfctant-rich phase of a small volume and a diluted aqueous phase,in which the suarfctant concentration is close to the critical micellar concentration (CMC). Any analyte solubilized in the hydrophobic core of the micelles will be separated and concentrated in the small volume of the suarfctant-rich phase. The small volume of the surfactant-rich phase obtained with this methodology permits design of extraction schemes that are simpler, more economical and efficient, lower toxicity to the environment than those extractions that use organic solvents. Separation and preconcentration based on cloud point extraction is becoming an important and practical application in the use of surfactants in analytical chemistry. Cloud point extraction is widely used in the separation and purification of bio-molecules and extraction of organic compounds and metal ions, and find important and practical applications in analytical chemistry.The aim of this dissertation is to systematically study on the cloud-point extraction and its application to the separation/preconcerntration and determination of some hazardous substances in water samples using partial least squares methods by spectrophotometry. The major contents are described as follows:(1) Simultaneous spectrophotometric determination of trace amount of malachite green and crystal violet in water after cloud point extraction using partial least squares regressionIn this work, a new method has been proposed to simultaneously determine trace amount of malachite green and crystal violet from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression. The optimal extraction and operating conditions, such as pH, reagents concentration and effect of time and temperature, and so on, have been investigated using the non-ionic surfactant Triton X-114. The maximum absorption wavelength for malachite green and crystal violet is 624 nm and 579 nm, respectively; linearity is obeyed in the range of 9.9-800 ng mL-1 and 16-1000 ng mL-1 with detection limit of 2.9 ng mL?1 and 4.8 ng mL?1, and the root mean square error of prediction (RMSEP) are 0.0197 and 0.0325, respectively. The proposed method has been applied successfully to simultaneously determine trace amount of malachite green and crystal violet in real matrix samples with the recoveries of 92.45% -102.5%.(2) Cloud point extraction and simultaneous spectrophotometric determination of V (V), Co (II) and Cu (II) ions in water samples by 5-Br-PADAP using partial least squares regressionIn this work, a new method has been proposed to simultaneously determine V (V), Co (II) and Cu (II) ions from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression. The method is based on the color reaction of these ions with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (5-Br-PADAP) and subsequent micelle mediated extraction of the products. The optimal extraction and operating conditions, such as pH, reagents concentration and effect of time and temperature, and so on, have been investigated using the non-ionic surfactant Triton X-114. The maximum absorption wavelength for the chelates of V (V), Co (II) and Cu (II) ions is 603 nm, 588 nm and 563 nm, respectively; Linearity is obeyed in the range of 7-300, 3-100 and 15-700 ng mL-1 for V (V), Co (II) and Cu (II), with the detection limit of 2.2, 1.0 and 4.5 ng mL-1, and the root mean square error of prediction (RMSEP) for applying the PLS method to 15 synthetic samples in the linear ranges of these metal ions was 0.0034, 0.0016 and 0.0181, respectively. The interference effect of some anions and cations was also tested. The proposed method has been applied successfully to the simultaneous determination of V (V), Co (II) and Cu (II) ions in real matrix samples with the recoveries of 96.75% -104.7%.(3) Cloud point extraction and simultaneous spectrophotometric determination of uranium and thorium in water samples by Arsenazo III using partial least squares regression In this work, a new method has been proposed to simultaneously determine the uranium (VI) and thorium (IV) from aqueous solution by spectrophotometry after cloud point extraction using partial least squares regression. The method is based on the color reaction of these ions with Arsenazo III and subsequent micelle mediated extraction of products. The optimal extraction and operating conditions, such as pH, reagents concentration and effect of time and temperature, and so on, have been investigated using the non-ionic surfactant Triton X-114. The maximum absorption wavelength for the chelates of uranium and thorium ions is 653 nm and 662 nm, respectively; linearity is obeyed in the range of 0.16-5.0μg mL-1 and 0.25-3.5μg mL-1 with detection limit of 0.05μg mL-1 and 0.08μg mL-1, and the root mean square error of prediction (RMSEP) are 0.0435 and 0.0789, respectively. The proposed method has been applied successfully to simultaneously determine the uranium and thorium in real matrix samples with the recoveries of 90.70% -106.4%.