| The liquid-phase microextraction (LPME) has been developed to be a new environmentally benign sample preparation technique which integrates sampling, extraction and concentration in to a single step, which was introduced by Dasgupta and Cantwen in 1996. It is proved to be simple, low-cost and virtually solvent-free method. Also it can provide excellent sample clean-up effect, high extraction recovery and enrichment factors. The technique is suitable for extracting the trace target analytes in various sample of material evidence. With the development of LPME in the past decade, it can be performed in different modes, including single-drop microextraction, liquid-liquid-liquid microextraction, hollow fibers-protected LPME (HF-LPME), headspace LPME (HS-LPME), dynamic LPME and dispersive liquid-liquid microextraction (DLLME). Of which, DLLME is the latest one. Due to its advantages such as high extraction efficiency and flexibility, LPME has been widely used in environmental, food, fragrance, flavor, forensic, pharmaceutical and biological analysis.Capillary electrophoresis (CE) provides original characteristics in terms of separation mechanisms, rapid and efficient analysis with very high resolution, small sample consumption, high sample throughput, low operational cost and tolerance to biological matrices. All these characteristics ideally make it an attractive technique in comparison with gas chromatography and liquid chromatography for forensic toxicological analysis. However, poor concentration sensitivity of traditional CE with on-column UV detection due to low sample injection volume and short optical path-length limit the use of CE as an effective method to determine trace analytes in various sample of material evidence. To improve concentration detection limits in CE, it is essential for extraction and clean-up of samples prior to CE.In the present study, the advantages of LPME and CE were integrated to determine trace analytes in various samples of material evidence. This method furtherly developed the application of LPME and CE in forensic science.In the first part of this thesis, a detailed review concerning the development of LPME, CE and their applications in the forensic analysis are presented.In the second part,a new method is described for the simultaneous derivatization and extraction of free cyanide in biological samples using HF-HS-LPME followed by CE determination. Parameters affecting extraction efficiency and CE conditions were investigated and optimized. The calibration curve was linear for concentrations of CN? in the range from 0.1 to 20μmol/L (r = 0.9987). The limits of detection (LODs, S/N = 3) was estimated to be 0.03μmol/L of CN? concentration. Such a detection sensitivity is high enough for free cyanide determination in common environmental and biological samples. Excellent repeatability of the extraction (RSD≤5.6%, n = 5) was achieved. The feasibility of this method was demonstrated by analyzing human urine and saliva samples with spiked recoveries in the range of 92-103.4%.In the third part, a new method was developed for pre-concentration and determination of multiple drugs of abuse in human urine and hair using DLLME and CE with UV detection (CE-UV). Parameters affecting extraction efficiency and CE conditions were investigated and optimized. Under optimum conditions, linearity of the method was observed for all target analytes in the range from 0.15 to 6000μg/L with the correlation coefficient (r) ranging from 0.9986 to 0.9994. The LODs (S/N = 3) were estimated to be in the range from 0.055 to 0.135μg/L. Excellent repeatability of the extraction (RSD≤4.0%, n = 5) was achieved. The feasibility of this method was demonstrated by analyzing biological samples with spiked recoveries in the range of 85.0~99.4% (RSD≤7.1%, n = 5).In the fourth part, a new method was developed for pre-concentration, chiral separation and determination of multiple illicit drugs on forensic samples using DLLME and CE-UV. Parameters affecting extraction efficiency and CE conditions were investigated and optimized. Under optimum conditions, linearity of the method was observed for all target analytes in the range from 0.15 to 6500μg/L with the correlation coefficient (r) ranging from 0.9981 to 0.9994. The LODs (S/N = 3) were estimated to be in the range from 0.05 to 0.20μg/L. Excellent repeatability of the extraction (RSD≤4.4%, n = 5) was achieved. The feasibility of this method was demonstrated by analyzing on forensic seized samples, such as banknote, kraft paper, plastic bag and silver paper, with spiked recoveries in the range of 85.9-95.4% (RSD≤4.7%, n = 5). |
PDF Full Text Request