| Sample pretreatment technology is the most critical procedure in sample analysis,especially in trace analysis of organic pollutants in complex samples. Sample pretreatmentprocess directly influences the speed of sample analysis and accuracy and precision of theresults. Recently, the development of rapid, simple, less solvent consumption,miniaturization, automation, and easy combination to analytical instruments are theimportant trend of sample pretreatment technology. The automation of samplepretreatment devices is one of the hot points in analytical chemistry.Liquid-phase microextraction has emerged as a new sample preparation techniquebased on solvent-miniaturization because of the obvious advantages of simple, low cost,efficiency, selectivity, high enrichment factor, excellent sample clean-up, easycombination to analytical instruments and automation. It combines extraction,concentration and clean-up in a single step and it is a sensitive and environmental friendlysample preparation technique. Based on properties of the target analytes and types of thereal samples, different extraction modes can be chosen for efficient and fast analysis. Ithas been widely used in trace analysis of organic pollutants in complex samples.This work focuses on the development of a novel automated liquid-phasemicroextraction device combined with HPLC and its applications in environmental watersamples, dairy samples, feed samples and soil samples analysis based on differentextraction modes. The main contents are as follows：(1) A novel automated liquid-phase microextraction device was developed based onvirtual instrument technology. Hardware systems of liquid flow-driven system, liquid flowpath switching system, and pipeline system were established. The control software waswritten. It will improve the accuracy and precision of liquid phase microextrction.(2) A novel analytical method for determination of Phenol,4-NP and2,4-DCP inwater samples, based on liquid-liquid-liquid microextraction combined with HPLC wasdeveloped. The optimal conditions were as follows:1-Octanol as extraction solvent, pH=5water sample as donor phase (containing50g/L of sodium chloride), sodium hydroxide of0.1mol/L as acceptor phase, stirring speed900rpm, extraction time20min, pump speed8 μL/s, dwell time30s. Under the optimal conditions, for three phenolic compounds,enrichment factors were85-101fold, and linearity was obtained in the range of20-1000ng/mL(R＞0.9981). The limits of detection defined for a signal-to-noise ratio of3(S/N=3) were0.9-2.2ng/mL. The relative standard deviations were below4.2%(n=6).This technique was successfully applied in the determination of phenolic compounds insurface water of East Lake, Wuhan. The recoveries from the spiked water sample variedbetween102.2and134.3%. Good reproducibilities were obtained with relative standarddeviation (RSD) values below4.5%.(3) A novel analytical method for determination of melamine in dairy samples, basedon liquid-liquid-liquid microextraction combined with HPLC was developed. The optimalconditions were as follows: Ultrasonic time15min,1-Octanol as extraction solvent, pH=8water sample as donor phase, pH=5ammonium sulphate of0.02mol/L as acceptor phase,stirring speed900rpm, extraction time15min, pump speed6μL/s. Under the optimalconditions, for melamine, enrichment factor was43fold, and linearity was obtained in therange of0.1-100μg/mL(R=0.9987). The limits of detection defined for a signal-to-noiseratio of3(S/N=3) were0.025μg/mL. The relative standard deviations were3.8%(n=6).This technique was successfully applied in the determination of melamine in real dairysamples. The recoveries from the spiked dairy samples varied between96.9and104.2%.Good reproducibilities were obtained with relative standard deviation (RSD) values below6.1%.(4) A novel analytical method for determination of TCs in feed samples, based oncarrier mediated liquid-liquid-liquid microextraction microextraction combined withHPLC was developed. The optimal conditions were as follows:1-Octanol as extractionsolvent (containing10%(w/v)of Aliquat-336as carrier), pH=9water sample as donorphase, pH=2hydrochloric acid as acceptor phase, stirring speed800rpm, extraction time15min, pump speed8μL/s, dwell time30s. Under the optimal conditions, for fourtetracycline antibiotics, enrichment factors were56-99fold, and linearity was obtained inthe range of1-500ng/mL (R＞0.9930). The limits of detection defined for asignal-to-noise ratio of3(S/N=3) were1.2-2.8ng/mL. The relative standard deviationswere below5.0%(n=6). This technique was successfully applied in the determination of real chicken feed samples. The recoveries from the spiked feed samples varied between95.6and115.6%. Good reproducibilities were obtained with relative standard deviation(RSD) values below5.6%.(5) A novel green analytical method for determination of PAHs in soil samples, basedon ultrasound-assisted extraction combined with liquid-phase microextraction technologyand HPLC was developed. The optimal ultrasonic conditions were as follows:1g soilsample adding15mL ultrapure water, in the room temperature, ultrasonic power100W,ultrasonic time10min. The optimal liquid-phase microextraction conditions were as follows:1-Octanol as acceptor phase and extraction solvent, stirring speed1000rpm, extraction time20min. Under the optimal conditions, the limits of detection of PAHs were in the range of0.05-0.1μg/g (S/N=3). Good linear range (0.5-50μg/g)(R＞0.9945)was obtained for allthe analytes. The relative standard deviations were below5.0%(n=6). This technique wassuccessfully applied in the determination of PAHs in soil samples of a dye factory inWuhan. The recoveries from the spiked soil samples varied between78.4and127.3%.Good reproducibilities were obtained with relative standard deviation (RSD) values below8.5%. |
