Study On A Combination Of Solid Phase Extraction And Dispersive Liquid-liquid Microextraction Technique And Its Application

The analyses in environment and food samples have the characteristics of complex matrix effect interferences, low levels of analytes and the limited sensitivity. Sample preparation step plays an important role in improving the selectivity and sensitivity of analysis methods, and its main aim is to extract, separate and concentrate the analytes of interest. In this paper, a sample pretreatment method, solid-phase extraction combined with dispersive liquid-liquid microextraction (SPE-DLLME) was established. SPE has the advantages such as simplicity, high speed, less consumption of organic solvents and high reproducibility. DLLME method has the advantages such as simplicity of operation, rapidity, low cost, high recovery and enrichment factor and environmental benignity. SPE combined with DLLME not only offers the ability to isolate the target analytes from the complex samples and reduce the matrix effect and water-soluble interferences, but the possibility to provide a very high enrichment factor. Meanwhile, the different extraction modes were explored when ACN-CH2Cl2mixture solution was chosen as eluent. The SPE-DLLME technique has more advantages and the field of SPE-DLLME application was clearly expanded.The main content of this paper is as follows:(1) A SPE-DLLME method was established for the sensitive determination of carbamates (carbofuran. carbaryl and pirimicarb) in environment aqueous samples, apple and cucumber samples. Some important extraction parameters affecting the performance of the two processes, such as sample solution flow rate, breakthrough volume, sample pH. the salt addition, as well as type and volume of the elution solvent were thoroughly investigated and optimized. The new method provided an ultra enrichment factors (EFs) for carbamates ranged from5408to7647. The method was applied for the selective extraction of carbamates in water, apple and cucumber samples under the optimum SPE-DLLME and HPLC conditions. The linear ranges for carbofuran and carbaryl were0.05-5μg L-1in water samples and0.25-100μg kg-1in apple and cucumber samples while for pirimicarb were0.01-5μg L-1in water samples and0.10-100μg kg-1in apple and cucumber samples with the correlation coefficient of above0.9978. The limits of detections (LODs) of carbofuran, carbaryl and pirimicarb were calculated to be0.01,0.01and0.001μg L-1in water samples0.06,0.06and0.005μg L-1in both apple and cucumber samples. The proposed method was successfully applied for the selective extraction and determination of carbamates in natural water, apple and cucumber.(2) A novel SPE-DLLME technique as a sample-preparation method for PAHs in smoked bacon samples was established. Three PAHs including naphthalene (Naph), phenanthrene (Phen), and pyrene (Pyr) were chosen as the model analytes to investigate the viability of improved SPE-DLLME technique. It was the first time to use ACN-CH2Cl2mixture solution as eluent in the study. Compared with the use of methanol or acetonitrile as eluent, a remarkable improvement in elution efficiency was achieved. Also, the mixture eluent gave a perfect combination of both SPE and DLLME procedure. Some important extraction parameters affecting the performance, such as the sample solution flow rate, breakthrough volume, the salt addition, as well as type and volume of the elution solvent were thoroughly investigated and optimized. The optimized method was applied to determine PAHs in smoked bacon samples to evaluate the application of this method to real food samples. The developed method provided an ultra enrichment factors (EFs) for PAHs ranged from3478to3824. The method was applied for the selective extraction and sensitive determination of PAHs in smoked bacon samples under the optimum SPE-DLLME-HPLC conditions. The linear ranges were0.25-160μg kg-1for the three PAHs in smoked bacon samples with the correlation coefficient of above0.9989. The limit of detections (s/n=3) were0.05,0.01,0.02μg kg-1for Naph, Phen. Pyr, respectively. Both the intra-day and inter-day precisions (RSDs) were<10%.(3) A DSPE-DLLME method was established for the sensitive determination of PAHs including naphthalene(Naph), Fluorene(Flu), Anthracene(Anth), pyrene (Pyr) and Fluoranthene (Fluo) in sediment samples. Some important extraction parameters affecting the performance of the process, such as the usage of C18material, extraction time, as well as type, volume and proportion of the ACN-CH2Cl2mixure elution solvent were thoroughly investigated and optimized. The new method provided an ultra enrichment factors (EFs) for PAHs ranged from1377to1483. The method was applied for the selective extraction of PAHs in sediment samples under the optimum DSPE-DLLME-HPLC conditions. The limits of detections (LODs) of five PAHs were ranged from0.05μg kg-1to0.4μg kg-1. The proposed method was successfully applied for the selective extraction and determination of PAHs in sediment samples.