ABSTRACT
In this paper, counter current salting-out homogenous liquid-liquid extraction was combined with dispersive liquid-liquid microextraction for the determination of environmental estrogens in water samples by high-performance liquid chromatography. In this method, initially, sodium chloride was filled into a syringe and a mixture of water sample and acetonitrile was driven to pass through the syringe. Due to salting-out effect, fine droplets of acetonitrile went up through the remaining mixture and aggregated as a separated layer on the top. Then, the collected organic phase (acetonitrile) was removed with a syringe and mixed with carbon tetrachloride (extraction solvent). In the second step, the mixed organic phase was rapidly injected into 5 mL of distilled water to further enrich the analytes. Good linearity was obtained in the concentration range of 2.0~200 ng/mL for diethylstilbestrol (DES) and 8.0~200 ng/mL for octylphenol (OP), respectively. Limits of detection were 0.09 ng/mL for DES and 0.20 ng/mL for OP, respectively. Relative standard deviations for intra- and inter-day precisions were less than 2.1 and 3.1%, respectively. Finally, the established method was successfully applied to determine DES and OP in river water, well water, bottled water and campus drinking water samples with recoveries in the range from 81.0 to 105.9%.
Subject(s)
Estrogens/analysis , Estrogens/isolation & purification , Liquid Phase Microextraction/methods , Water Pollutants, Chemical/analysis , Water Pollutants, Chemical/isolation & purification , Chromatography, High Pressure Liquid , Drinking Water/analysis , Limit of DetectionABSTRACT
In this paper, methylamine modified graphene (CH3NH-G) was synthesized and used as solid-phase extraction (SPE) sorbent to cleanup the acetonitrile extract of sunflower seeds for the determination of neonicotinoid insecticides by UPLC-MS/MS. The effects of the type of extraction solvent, pH, the amount of CH3NH-G sorbent as well as the type and volume of eluent on the extraction efficiency were evaluated. Good linearity was obtained for the analytes with coefficient of determination (R2) in the range of 0.9986-0.9998. LOD (S/N=3) and LOQ (S/N=10) were below 6 and 20ngkg-1, respectively. Method recoveries were between 74.3% and 119.1%. Relative standard deviations (RSD) for eight replicate determinations were in the range of 1.7-2.9%. The proposed method has been applied to the analysis of 3 kinds of sunflower seed samples from local market.
Subject(s)
Chromatography, High Pressure Liquid/methods , Graphite/chemistry , Neonicotinoids/analysis , Seeds/chemistry , Solid Phase Extraction/methods , Tandem Mass Spectrometry/methods , Acetonitriles/chemistry , Helianthus/chemistry , Hydrogen-Ion Concentration , Insecticides/analysis , Insecticides/isolation & purification , Methylamines/chemistry , Neonicotinoids/isolation & purification , Reproducibility of ResultsABSTRACT
Graphene-based pipette tip solid-phase extraction was combined with ultra-high performance liquid chromatography and tandem mass spectrometry for the determination of carbamate pesticide residues in fruit juice samples. Four milligrams of graphene was used as sorbent material to pack a 1000 µL pipette tip for the extraction of pirimicarb, propoxur, isoprocarb, fenobucarb, and diethofencarb from 3 mL of fruit juice sample. The whole extraction process was finished in 12 min, and the volume of eluent used was only 1.5 mL. Under the optimized conditions, good linear relationship (R > 0.999) and lower limits of detection (0.0022-0.033 ng/mL) were achieved. The recoveries at three spiked levels ranged from 80.90 to 124.60% with relative standard deviations less than 4.88%. Compared with commercially available sorbents including propylsulfonic acid silica, graphitized carbon black, and C18 , graphene was superior in extraction efficiency. The proposed method is simple, rapid, sensitive, selective, and solvent saving.
