| After the capillary electrophoresis (CE) was developed, it has been widely used. However, the sensitivity of CE was low and the organic solvents immiscible in water can't be used in CE directly. So, the further application and development of CE were limited. In this thesis, the most popular preconcentration technique, homogeneous liquid-liquid microextraction, was fully described. At the same time, the running of organic solvents immiscible in water in CE was researched. This thesis consists of three sections:Chapter one:In this chapter, the reason of low sensitivity of CE was analyzed. Different methods were introduced to solve this problem. The homogeneous liquid-liquid microextraction was described in details. The principle, parameter, type and volume of the consolute solvent, type and volume of the extraction solvent, concentration of phase separator reagent and extraction time of this method were discussed. And then the possibility of analysis the organic solvent in CE directly and its advantages were discussed.Chapter two:A fast and effective preconcentration method for the extraction of o, m and p-nitrophenol was developed using a homogeneous liquid-liquid microextraction based on phase separation phenomenon. The extracted o, m and p-nitrophenol were determined using capillary electrophoresis. The phase separation phenomenon occurred by salt addition. After centrifugation, the extracting solvent was sedimented in the bottom of the conical test tube. The o, m and p-nitrophenol were transferred into the sedimented phase during the phase separation step. Phenols are hydrophobic in acidic solution. But under alkaline condition, they become deprotonated and present in hydrophilic salt forms. So, the pH should be considered before the phase separation step. Several factors such as, pH, volume of the consolute solvent, type and volume of the extraction solvent, concentration of phase separator reagent, extraction time influencing the extraction efficiency were investigated and optimized. The optimum conditions were as following:8 mL sample solution,1.8 mL consolute solvent (methanol), 220μL extraction solvent (dichloromethane), pH 1.5 and 22% NaCl (w/v). Under these conditions, the extraction recovery for o, m and p-nitrophenol were 64.7%,18.6% and 18.4%, respectively. The preconcentration factors were 103.6,29.8 and 29.4 for o, m and p-nitrophenol. Finally, the proposed method was successfully applied for the extraction and determination of the o, m and p-nitrophenol in waste water samples.Chapter three:The separation mode of CE was improved to run the organic solvents immiscible in water. Taking the determination of o, m and p-nitrophenol as an example, the running of organic solvents immiscible in water was confirmed. In this example, several factors, such as, type and volume of the extraction solvent, pH, type and volume of the consolute solvent, extraction time influencing the extraction efficiency were investigated and optimized. The optimum conditions were as following:0.3mL extraction solvent (n-octyl alcohol),300 L 3 mol/L HCl,900μL consolute solvent (ethanol). Under these conditions, the calibration curve, linear range, reproducibility, extraction recovery and preconcentration factors for o, m and p-nitrophenol can be obtained. At last, the proposed method was successfully applied for the extraction and determination of the o, m and p-nitrophenol in waste water samples. Given all the mentioned, it can be conclude that the running of organic solvents immiscible in water under this improved separation mode can be realized.
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