A sublimate sorbent for stir-bar sorptive extraction of aqueous endocrine disruptor pesticides for gas chromatography-electron capture detection.

A dumbbell-shaped magnetic stir-bar with sublimate sorbent was prepared for the stir bar sorptive extraction (SBSE) of pesticides in an aqueous sample prior to gas chromatography-micro-electron capture detection (GC-µECD). Cyclododecane (CDD) was coated onto a magnetic stir-bar surface as a sublimate sorbent, and steel balls were placed on both ends to form a dumbbell-shaped magnetic stir-bar for SBSE. Four EDC pesticides including chlorpyrifos, ethion, bromopropylate, and λ-cyhalothrin in aqueous samples were selected as model species to examine the proposed SBSE and the following desorption. The parameters studied were those affecting the extraction efficiencies including the coating (solvent for CDD and thickness), extraction (sample pH, stirring rate, time, and salting out effect), dissolution solvent volume, and the loss of CDD sublimated in air. The maximum extraction efficiency was obtained under the following conditions. The stir bar (with CDD thickness of 5.2 µm) was added into a 10 mL sample solution (at pH 7) for a 20-min extraction at 600 rpm. Then, the stir bar was gently removed from the sample solution, disassembled, and immersed into a 0.2 mL insert tube consisting of 3 µL hexane to dissolve; 1 µL was used for GC-ECD analysis. The linear ranges were 0.005-5 µg L-1 with coefficients of determination ranging from 0.9950 - 0.9994. Detection limits (based on S/N = 3) of the four EDCs were 0.4-4.5 ngL-1 with a relative standard deviation (RSD) of 2.4-6.3%, and quantitation limits (based on S/N = 5) were 1-15 ngL-1. The relative recoveries of the spiked samples were in the range of 83.2-98.7% with RSDs of 2.1-8.4% in farm field waters. The proposed sublimation sorbent obtained excellent enrichment factors (101-834) and provided a simple, rapid, sensitive, and eco-friendly sample preparation method.

Microwave-assisted decomplexation and in-situ headspace in-syringe dynamic derivatization of dimethylamine borane with high performance liquid chromatography-fluorescence detection.

A rapid, sensitive, selective, and simple method for monitoring dimethylamine borane (DMAB) in aqueous sample is proposed by combining microwave-assisted de-complexation, headspace liquid phase in-situ derivatization extraction, and high-performance liquid chromatography-fluorescence detection for the determination of DMAB in samples. The present procedure involves de-complexation of DMAB using microwave irradiation, evolution of dimethylamine (DMA) to the headspace from an alkalized sample solution, and dynamic headspace liquid-phase derivatization extraction (Dy-HS-LPDE) of DMA with 9-fluorenylmethyl chloroformate in a syringe barrel. In addition to the optimal Dy-HS-LPDE and chromatographic parameters described in our previous study, the de-complexation of DMAB by thermal and microwave-assisted procedures and evolution of DMA into the headspace from an alkalized solution and modification of the Dy-HS-LPDE method are thoroughly investigated. The results indicate that complete de-complexation was obtained at 70 °C for 5 min, 30 °C for 10 min, or using microwave irradiation for 30 s at any applied power. It indicates that the DMAB complex easily undergoes de-complexation under microwave irradiation. The linearity range was 0.01-0.5 mg L-1 for DMAB and 0.0077-0.38 mg L-1 for DMA, with a coefficient of determination of 0.9995, and limit of detection of 3 µg L-1 (limit of quantitation of 10 µg L-1) for DMAB. The recoveries of DMAB are 95.3% (3.0% RSD) for waste water when spiked 0.05 mg L-1 and 93.5% (5.4% RSD) for the samples spiked with copper and nickel salts (5 mM each in the spiked waste sample). The whole analytical procedure can be completed within 25 min. The results confirm that the present method is a rapid, sensitive, selective, automated, low-cost and eco-friendly procedure to identify DMAB in samples.

Bis(phenylidenebenzeneamine)-1-disulfide Derivatives Induce Autophagy in Melanoma Cells Through a Mitochondria-mediated Pathway.

We have previously reported the efficient synthesis of bis(phenylidenebenzeneamine)-1-disulfide derivatives 1-8. In the present article, we delineated the signaling pathways involved in the anticancer effects of compound 2 on melanoma cells. The treatment of melanoma cells with compound 2 resulted in ROS generation, a decrease in ΔΨmt, ATP, and protein expression of mitochondrial respiratory chain subunits. In addition, no significant apoptotic or necrotic effect was seen following compound 2 treatment using an annexin V and propidium iodide (PI) double-staining. Nevertheless, autophagy-related proteins LC3 and Beclin 1 were enhanced by compound 2. Furthermore, compound 2 was also shown to reduce murine melanoma size in a mouse model. We revealed a novel bio-evaluation of bis(phenylidenebenzeneamine)-1-disulfide derivatives anti-tumor proliferation mechanism and suggest that these agents may have potential chemotherapeutic activity for melanoma cells.

Complexation-flocculation combined with microwave-assisted headspace solid-phase microextraction in determining the binding constants of hydrophobic organic pollutants to dissolved humic substances.

The binding constants, KDOC, of selected polycyclic aromatic hydrocarbons (PAHs)-phenanthrene, anthracene, fluoranthene, and pyrene-to dissolved humic substances (DHS) were determined by complexation-flocculation combined with microwave-assisted headspace solid-phase microextraction (CF-MA-HS-SPME). The results obtained are comparable with KDOC data reported in the literature. No disruption of the PAH to DHS binding equilibrium was observed during the complexation-flocculation process. The present study, which is the first to determine KDOC by CF-MA-HS-SPME, provides an alternative approach to determine the KDOC of PAHs. CF-MA-HS-SPME provides some advantages over other methods, such as no limitation of fluorescent compounds, greater determination speed, and the capability of measuring various compounds simultaneously.

A novel fatty-acid-based in-tube dispersive liquid-liquid microextraction technique for the rapid determination of nonylphenol and 4-tert-octylphenol in aqueous samples using high-performance liquid chromatography-ultraviolet detection.

In this study, a novel fatty-acid-based in-tube dispersive liquid-liquid microextraction (FA-IT-DLLME) technique is proposed for the first time and is developed as a simple, rapid and eco-friendly sample extraction method for the determination of alkylphenols in aqueous samples using high-performance liquid chromatography-ultraviolet detection (HPLC-UV). In this extraction method, medium-chain saturated fatty acids were investigated as a pH-dependent phase because they acted as either anionic surfactants or neutral extraction solvents based on the acid-base reaction caused solely by the adjustment of the pH of the solution. A specially designed home-made glass extraction tube with a built-in scaled capillary tube was utilized as the phase-separation device for the FA-IT-DLLME to collect and measure the separated extractant phase for analysis. Nonylphenol (NP) and 4-tert-octylphenol (4-tOP) were chosen as model analytes. The parameters influencing the FA-IT-DLLME were thoroughly investigated and optimized. Under the optimal conditions, the detector responses of NP and 4-tOP were linear in the concentration ranges of 5-4000 µg L(-1), with correlation coefficients of 0.9990 and 0.9996 for NP and 4-tOP, respectively. The limits of detection based on a signal-to-noise ratio of 3 were 0.7 and 0.5 µg L(-1), and the enrichment factors were 195 and 143 for NP and 4-tOP, respectively. The applicability of the developed method was demonstrated for the analysis of alkylphenols in environmental wastewater samples, and the recoveries ranged from 92.9 to 107.1%. The extraction process required less than 4 min and utilized only acids, alkalis, and fatty acids to achieve the extraction. The results demonstrated that the presented FA-IT-DLLME approach is highly cost-effective, simple, rapid and environmentally friendly in its sample preparation.

Rapid microwave assisted synthesis of graphene nanosheets/polyethyleneimine/gold nanoparticle composite and its application to the selective electrochemical determination of dopamine.

In this study, a simple and fast microwave assisted chemical reduction method for the preparation of graphene nanosheet/polyethyleneimine/gold nanoparticle (GNS/PEI/AuNP) composite was developed. PEI, a cationic polymer, was used both as a non-covalent functionalizing agent for the graphene oxide nanosheets (GONSs) through electrostatic interactions in the aqueous medium and also as a stabilizing agent for the formation of AuNPs on PEI wrapped GNSs. This preparation method involves a simple mixing step followed by a simultaneous microwave assisted chemical reduction of the GONSs and gold ions. The prepared composite exhibits the dispersion of high density AuNPs which were densely decorated on the large surface area of the PEI wrapped GNS. X-ray photoelectron spectroscopy, powder X-ray diffraction, high-resolution transmission electron microscopy, field-emission scanning electron microscopy with energy dispersive X-ray spectroscopy, and thermo-gravimetric analysis, were used to characterize the properties of the resultant composite. The prepared GNS/PEI/AuNP composite film exhibited excellent electrocatalytical activity towards the selective determination of dopamine in the presence of ascorbic acid, which showed potential application in electrochemical sensors. The applicability of the presented sensor was also demonstrated for the determination of dopamine in human urine samples.

Effects of ultrasonic and microwave pretreatments on lipid extraction of microalgae.

The extraction of lipids from microalgal cells using ultrasonic and microwave pretreatments is mechanistically evaluated based on the distribution of cell fragments, the lipid content analysis, the scanning electron microscopic (SEM) observation of ruptured microalgal cells, and the analysis of fatty acids. The results indicate that microwave pretreatment extracts lipids more rapidly and efficiently as compared to ultrasonic pretreatment. The rupture of cells in the microwave process is due to the tremendous pressure caused by the rapid heating of the moisture inside the microalgal cells, whereas in the ultrasonic process the microalgal cells are ruptured by shock waves from cavitation bubbles outside the cells. The fatty acid composition of the respective lipids extracted via the two types of pretreatment did not vary significantly from one another. These results demonstrate that the microwave process is rapid and more effective than the ultrasonic process for lipid extraction from microalgae.

Novel solvent-free microwave-assisted extraction coupled with low-density solvent-based in-tube ultrasound-assisted emulsification microextraction for the fast analysis of organophosphorus pesticides in soils.

A novel and rapid solventless microwave-assisted extraction coupled with low-density solvent-based in-tube ultrasound-assisted emulsification microextraction has been developed for the efficient determination of nine organophosphorus pesticides in soils by GC analysis with microelectron capture detection. A specially designed, homemade glass tube inbuilt with a scaled capillary tube was used as an extraction device to collect and measure the separated extractant phase easily. Parameters affecting the efficiencies of the developed method were thoroughly investigated. From experimental results, the following conditions were selected for the extraction of organophosphorus pesticides from 1.0 g of soil sample to 5 mL of aqueous solution under 226 W of microwave irradiation for 2.5 min followed by ultrasound-assisted emulsification microextraction with 20 µL toluene for 30 s and then centrifugation at 3200 rpm for 3 min. Detections were linear in the range of 0.25-10 ng/g with detection limits between 0.04 and 0.13 ng/g for all target analytes. The applicability of the method to real samples was assessed on agricultural contaminated soils and the recoveries ranged between 91.4 and 101.3%. Compared to other methods, the present method was shown to be highly competitive in terms of sensitivity, cost, eco-friendly nature, and analysis speed.

Novel one-step headspace dynamic in-syringe liquid phase derivatization-extraction technique for the determination of aqueous aliphatic amines by liquid chromatography with fluorescence detection.

A novel one-step headspace (HS) dynamic in-syringe (DIS) based liquid-phase derivatization-extraction (LPDE) technique has been developed for the selective determination of two short-chain aliphatic amines (SCAAs) in aqueous samples using high performance liquid chromatography (HPLC) with fluorescence detection (FLD). Methylamine (MA) and dimethylamine (DMA) were selected as model compounds of SCAAs. In this method, a micro-syringe pre-filled with derivatizing reagent solution (9-fluorenylmethyl chloroformate) in the barrel was applied to achieve the simultaneous derivatization and extraction of two methylamines evolved from alkalized aqueous samples through the automated reciprocated movements of syringe plunger. After the derivatization-extraction process, the derivatized phase was directly injected into HPLC-FLD for analysis. Parameters influencing the evolution of methylamines and the HS-DIS-LPDE efficiency, including sample pH and temperature, sampling time, as well as the composition of derivatization reagent, reaction temperature, and frequency of reciprocated plunger movements, were thoroughly examined and optimized. Under optimal conditions, detections were linear in the range of 25-500µgL(-1) for MA and DMA with correlation coefficients all above 0.995. The limits of detection (based on S/N=3) were 5 and 19ngmL(-1) for MA and DMA, respectively. The applicability of the developed method was demonstrated for the determination of MA and DMA in real water samples without any prior cleanup of the sample. The present method provides a simple, selective, automated, low cost and eco-friendly procedure to determine aliphatic amines in aqueous samples.

Rapid determination of triclosan in personal care products using new in-tube based ultrasound-assisted salt-induced liquid-liquid microextraction coupled with high performance liquid chromatography-ultraviolet detection.

This paper describes the development of a novel, simple and efficient in-tube based ultrasound-assisted salt-induced liquid-liquid microextraction (IT-USA-SI-LLME) technique for the rapid determination of triclosan (TCS) in personal care products by high performance liquid chromatography-ultraviolet (HPLC-UV) detection. IT-USA-SI-LLME method is based on the rapid phase separation of water-miscible organic solvent from the aqueous phase in the presence of high concentration of salt (salting-out phenomena) under ultrasonication. In the present work, an indigenously fabricated home-made glass extraction device (8-mL glass tube inbuilt with a self-scaled capillary tip) was utilized as the phase separation device for USA-SI-LLME. After the extraction, the upper extractant layer was narrowed into the self-scaled capillary tip by pushing the plunger plug; thus, the collection and measurement of the upper organic solvent layer was simple and convenient. The effects of various parameters on the extraction efficiency were thoroughly evaluated and optimized. Under optimal conditions, detection was linear in the concentration range of 0.4-100ngmL(-1) with correlation coefficient of 0.9968. The limit of detection was 0.09ngmL(-1) and the relative standard deviations ranged between 0.8 and 5.3% (n=5). The applicability of the developed method was demonstrated for the analysis of TCS in different commercial personal care products and the relative recoveries ranged from 90.4 to 98.5%. The present method was proven to be a simple, sensitive, less organic solvent consuming, inexpensive and rapid procedure for analysis of TCS in a variety of commercially available personal care products or cosmetic preparations.

Advanced glycation end product Nε-carboxymethyllysine induces endothelial cell injury: the involvement of SHP-1-regulated VEGFR-2 dephosphorylation.

N(ε)-carboxymethyllysine (CML), a major advanced glycation end product, plays a crucial role in diabetes-induced vascular injury. The roles of protein tyrosine phosphatases and vascular endothelial growth factor (VEGF) receptors in CML-related endothelial cell injury are still unclear. Human umbilical vein endothelial cells (HUVECs) are a commonly used human EC type. Here, we tested the hypothesis that NADPH oxidase/reactive oxygen species (ROS)-mediated SH2 domain-containing tyrosine phosphatase-1 (SHP-1) activation by CML inhibits the VEGF receptor-2 (VEGFR-2, KDR/Flk-1) activation, resulting in HUVEC injury. CML significantly inhibited cell proliferation and induced apoptosis and reduced VEGFR-2 activation in parallel with the increased SHP-1 protein expression and activity in HUVECs. Adding recombinant VEGF increased forward biological effects, which were attenuated by CML. The effects of CML on HUVECs were abolished by SHP-1 siRNA transfection. Exposure of HUVECs to CML also remarkably escalated the integration of SHP-1 with VEGFR-2. Consistently, SHP-1 siRNA transfection and pharmacological inhibitors could block this interaction and elevating [(3)H]thymidine incorporation. CML also markedly activated the NADPH oxidase and ROS production. The CML-increased SHP-1 activity in HUVECs was effectively attenuated by antioxidants. Moreover, the immunohistochemical staining of SHP-1 and CML was increased, but phospho-VEGFR-2 staining was decreased in the aortic endothelium of streptozotocin-induced and high-fat diet-induced diabetic mice. We conclude that a pathway of tyrosine phosphatase SHP-1-regulated VEGFR-2 dephosphorylation through NADPH oxidase-derived ROS is involved in the CML-triggered endothelial cell dysfunction/injury. These findings suggest new insights into the development of therapeutic approaches to reduce diabetic vascular complications.

Determination of ammonium in aqueous samples using new headspace dynamic in-syringe liquid-phase microextraction with in situ derivitazation coupled with liquid chromatography-fluorescence detection.

A new simultaneous derivatization and extraction method for the preconcentration of ammonia using new one-step headspace dynamic in-syringe liquid-phase microextraction with in situ derivatization was developed for the trace determination of ammonium in aqueous samples by liquid chromatography with fluorescence detection (LC-FLD). The acceptor phase (as derivatization reagent) containing o-phthaldehyde and sodium sulfite was held within a syringe barrel and immersed in the headspace of sample container. The gaseous ammonia from the alkalized aqueous sample formed a stable isoindole derivative with the acceptor phase inside the syringe barrel through the reciprocated movements of plunger. After derivatization-cum-extraction, the acceptor phase was directly injected into LC-FLD for analysis. Parameters affecting the ammonia evolution and the extraction/derivatization efficiency such as sample matrix, pH, temperature, sampling time, and the composition of derivatization reagent, reaction temperature, and frequency of reciprocated plunger, were studied thoroughly. Results indicated that the maximum extraction efficiency was obtained by using 100µL derivatization reagent in a 1-mL gastight syringe under 8 reciprocated movements of plunger per min to extract ammonia evolved from a 20mL alkalized aqueous solution at 70°C (preheated 4min) with 380rpm stirring for 8min. The detection was linear in the concentration range of 0.625-10µM with the correlation coefficient of 0.9967 and detection limit of 0.33µM (5.6ng mL(-1)) based on SN(-1)=3. The method was applied successfully to determine ammonium in real water samples without any prior cleanup of the samples, and has been proved to be a simple, sensitive, efficient and cost-effective procedure for trace ammonium determination in aqueous samples.

Rapid analysis of chlorinated anilines in environmental water samples using ultrasound assisted emulsification microextraction with solidification of floating organic droplet followed by HPLC-UV detection.

The present study demonstrates a simple, rapid and efficient method for the determination of chlorinated anilines (CAs) in environmental water samples using ultrasonication assisted emulsification microextraction technique based on solidification of floating organic droplet (USAEME-SFO) coupled with high performance liquid chromatography-ultraviolet (HPLC-UV) detection. In this extraction method, 1-dodecanol was used as extraction solvent which is of lower density than water, low toxicity, low volatility, and low melting point (24 °C). After the USAEME, extraction solvent could be collected easily by keeping the extraction tube in ice bath for 2 min and the solidified organic droplet was scooped out using a spatula and transferred to another glass vial and allowed to thaw. Then, 10 µL of extraction solvent was diluted with mobile phase (1:1) and taken for HPLC-UV analysis. Parameters influencing the extraction efficiency, such as the kind and volume of extraction solvent, volume of sample, ultrasonication time, pH and salt concentration were thoroughly examined and optimized. Under the optimal conditions, the method showed good linearity in the concentration range of 0.05-500 ng mL(-1) with correlation coefficients ranging from 0.9948 to 0.9957 for the three target CAs. The limit of detection based on signal to noise ratio of 3 ranged from 0.01 to 0.1 ng mL(-1). The relative standard deviations (RSDs) varied from 2.1 to 6.1% (n=3) and the enrichment factors ranged from 44 to 124. The proposed method has also been successfully applied to analyze real water samples and the relative recoveries of environmental water samples ranged from 81.1 to 116.9%.

Headspace solid phase microextraction in-situ supercritical fluid extraction coupled to gas chromatography-tandem mass spectrometry for simultaneous determination of perfluorocarboxylic acids in sediments.

Headspace solid phase microextraction (HS-SPME) in-situ supercritical fluid extraction (SFE) was investigated for the determination of trace amounts of perfluorocarboxylic acids (PFCAs) in sediments. Quantitation was performed by using gas chromatography coupled to negative chemical ionization-tandem mass spectrometry (GC-NCI-MS/MS). The optimum conditions of HS-SPME following SFE were obtained using 500 µL n-butanol as a derivatization reagent in supercritical carbon dioxide with static extraction for 10 min, then dynamic extraction for 20 min at 30 MPa and 70 °C and simultaneous collected with 100 µm film thickness PDMS fiber. The linear range of proposed method was from 5 to 5000 ng g(-1), with limit of detection ranging from 0.39 to 0.54 ng g(-1) and limit of quantitation ranging from 1.30 to 1.80 ng g(-1). The developed method was successfully applied to analyze PFCAs in sediments from rivers and beach near industrial areas. The concentrations of PFCAs determined are from 282 to 4473 ng g(-1).

A novel graphene nanosheets coated stainless steel fiber for microwave assisted headspace solid phase microextraction of organochlorine pesticides in aqueous samples followed by gas chromatography with electron capture detection.

In this study, a novel graphene nanosheets (GNSs) coated solid phase microextraction (SPME) fiber was prepared by immobilizing microwave synthesized GNSs on a stainless steel wire. Microwave synthesized GNSs were verified by X-ray diffraction, field emission-scanning electron microscopy (FE-SEM) and transmission electron microscope (TEM). GNS-SPME fiber was characterized using FE-SEM and the results showed the GNS coating was homogeneous, porous, and highly adherent to the surface of the stainless steel fiber. The performance and feasibility of the GNS-SPME fiber was evaluated under one-step microwave assisted (MA) headspace (HS) SPME followed by gas chromatography with electron capture detection for five organochlorine pesticides (OCPs) in aqueous samples. Parameters influencing the extraction efficiency of MA-HS-GNS-SPME such as microwave irradiation power and time, pH, ionic strength, and desorption conditions were thoroughly examined. Under the optimized conditions, detection limits for the OCPs varied between 0.16 and 0.93 ng L(-1) and linear ranges varied between 1 and 1500 n gL(-1), with correlation coefficients ranging from 0.9984 to 0.9998, and RSDs in the range of 3.6-15.8% (n=5). In comparison with the commercial 100 µm polydimethylsiloxane fiber, the GNS coated fiber showed better extraction efficiency, higher mechanical and thermal stability (up to 290°C), longer life span (over 250 times), and lower production cost. The method was successfully applied to the analysis of real water samples with recoveries ranged between 80.1 and 101.1% for river water samples. The results demonstrated that the developed MA-HS-GNS-SPME method was a simple, rapid, efficient pretreatment and environmentally friendly procedure for the analysis of OCPs in aqueous samples.

Determination of alachlor and its metabolite 2,6-diethylaniline in microbial culture medium using online microdialysis enriched-sampling coupled to high-performance liquid chromatography.

In this study, a simple and novel microdialysis sampling technique incorporating hollow fiber liquid phase microextraction (HF-LPME) coupled online to high-performance liquid chromatography (HPLC) for the one-step sample pretreatment and direct determination of alachlor (2-chloro-2',6'-diethyl-N -(methoxymethyl)acetanilide) and its metabolite 2,6-diethylaniline (2,6-DEA) in microbial culture medium has been developed. A reversed-phase C-18 column was utilized to separate alachlor and 2,6-DEA from other species using an acetonitrile/water mixture (1:1) containing 0.1 M phosphate buffer solution at pH 7.0 as the mobile phase. Detection was carried out with a UV detector operated at 210 nm. Parameters that influenced the enrichment efficiency of online HF-LPME sampling, including the length of the hollow fiber, the perfusion solvent and its flow rate, the pH, and the salt added in sample solution, as well as chromatographic conditions were thoroughly optimized. Under optimal conditions, excellent enrichment efficiency was achieved by the microdialysis of a sample solution (pH 7.0) using hexane as perfusate at the flow rate of 4 µL/min. Detection limits were 72 and 14 ng/mL for alachlor and 2,6-DEA, respectively. The enrichment factors were 403 and 386 (RSD < 5%) for alachlor and 2,6-DEA, respectively, when extraction was performed by using a 40 cm regenerated cellulose hollow fiber and hexane as perfusion solvent at the flow rate of 0.1 µL/min. The proposed method provides a sensitive, flexible, fast, and eco-friendly procedure to enrich and determine alachlor and its metabolite (2,6-DEA) in microbial culture medium.

Determination of pyrethroid metabolites in human urine using liquid phase microextraction coupled in-syringe derivatization followed by gas chromatography/electron capture detection.

Metabolites of synthetic pyrethroids such as cis-3-(2,2-dibromovinyl)-2,2-di-methylcyclo-propane-1-carboxylic acid, cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid), 3-phenoxybenzoic acid (3-PBA), and 4-fluoro-3-PBA are biomarkers for exposure to phenothrin, tetramethrin, cyfluthrin, cypermethrin, deltamethrin, and permethrin. In this study, the pyrethroid metabolites in workers' urine samples were monitored for the first time with a novel sample pretreatment process combining hollow fiber liquid phase microextraction (HF-LPME) and in-syringe derivatization (ISD) followed by gas chromatography-electron capture detector (GC-ECD) analysis. A micro-syringe pre-filled with derivatizing agents and syringe needle connected to an extracting solvent impregnated hollow fiber segment was used as the LPME probe. Pyrethroid metabolites were extracted and enriched simultaneously from urine samples by HF-LPME sampling and acid hydrolysis at 70 °C for 10 min. After sampling, the ISD was performed by mixing the extracting solution and derivatizing agents through plunger movements, followed by GC-ECD analysis. Parameters influencing the HF-LPME efficiency and ISD were investigated and optimized. Under optimum conditions, the method provided enrichment factors of 69.8-154.6, repeatability from 5.0 to 12% (n = 5), and good linearity (R(2) = 0.9980-0.9998) for interested analytes spiked in urine samples. The method detection limits ranged from 1.6 to 17 ng/mL. A comparison was performed between the proposed method and conventional methods. The proposed method was applied to analyze pyrethroid metabolites in the urine samples collected from workers of pesticide formulation plants. The results suggested that the proposed HF-LPME coupled ISD method was a rapid, simple, efficient, and eco-friendly technique in the biomonitoring of metabolites of pyrethroids in workers' urine.

Rapid determination of dichlorodiphenyltrichloroethane and its main metabolites in aqueous samples by one-step microwave-assisted headspace controlled-temperature liquid-phase microextraction and gas chromatography with electron capture detection.

A rapid and sensitive analytical method for the determination of dichlorodiphenyltrichloroethane (DDT) and its main metabolites in environmental aqueous samples has been developed using one-step microwave-assisted headspace controlled-temperature liquid-phase micro-extraction (MA-HS-CT-LPME) technique coupled with gas chromatography-electron-capture detection (GC-ECD). In this study, the one-step extraction of DDT and its main metabolites was achieved by using microwave heating to accelerate the evaporation of analytes into the controlled-temperature headspace to form a cloudy mist vapor zone for LPME sampling. Parameters influencing extraction efficiency were thoroughly optimized, and the best extraction for DDT and its main metabolites from 10-mL aqueous sample at pH 6.0 was achieved by using 1-octanol (4-µL) as the LPME solvent, sampling at 34°C for 6.5 min under 249W of microwave irradiation. Under optimum conditions, excellent linear relationship was obtained in the range of 0.05-1.0 µg/L for 1-dichloro-2,2-bis-(p'-chlorophenyl)ethylene (p,p'-DDE), 0.1-2.0 µg/L for o,p'-DDT, 0.15-3.0 µg/L for 1,1-dichloro-2,2-bis-(p'-chlorophenyl)ethane (p,p'-DDD) and p,p'-DDT, with detection limits of 20 ng/L for p,p'-DDE, and 30 ng/L for o,p'-DDT, p,p'-DDD and p,p'-DDT. Precision was in the range of 3.2-11.3% RSD. The proposed method was validated with environmental water samples. The spiked recovery was between 95.5% and 101.3% for agricultural-field water, between 94% and 99.7% for sea water and between 93.5% and 98% for river water. Thus the established method has been proved to be a simple, rapid, sensitive, inexpensive and eco-friendly procedure for the determination of DDT and its main metabolites in environmental water samples.

Determination of organophosphorous pesticides in water using in-syringe ultrasound-assisted emulsification and gas chromatography with electron-capture detection.

An in-syringe ultrasound-assisted emulsification microextraction (USAEME) was developed for the extraction of organophosphorus pesticides (OPPs) from water samples. The OPPs subsequently analyzed gas chromatography (GC) using a microelectron capture detector (muECD). Ultrasound radiation was applied to accelerate the emulsification of microL-level low-density organic solvent in aqueous solutions to enhance the microextraction efficiency of OPPs in the sample preparation for GC-muECD. Parameters affecting the efficiency of USAEME, such as the extraction solvent, solvent volume, pH, salt-addition, and extraction time were thoroughly investigated. Based on experimental results, OPPs were extracted from a 5mL aqueous sample by the addition of 20microL toluene as the extraction solvent, followed by ultrasonication for 30s, and then centrifugation for 3min at 3200rpm, offered the best extraction efficiency. Detections were linear in the concentration of 0.01-1microg/L with detection limits between 1ng/L and 2ng/L for OPPs. Enrichment factors ranged from 330 to 699. Three spiked aqueous samples were analyzed, and recovery ranged from 90.1% to 104.7% for farm-field water, and 90.1% to 101.8% for industrial wastewater. The proposed method provides a simple, rapid, sensitive, inexpensive, and eco-friendly process for determining OPPs in water samples.

On-line microdialysis coupled solid-phase extraction to decrease matrix interference in the HPLC analysis of urinary ketamine and its metabolites.

A microdialysis sampling (MDS) on-line SPE (MDS/SPE) has been applied to redeem the detection after dilution to decrease matrix interference in the analysis of ketamine (K) and its two main metabolites, norketamine (NK) and dehydronorketamine (DHNK) in urine by HPLC. After being filtrated, diluted and adjusting the pH, K and its metabolites in the diluted sample solution were collected through MDS and then trapped on an on-line SPE for HPLC analysis. The optimal conditions for MDS/SPE were investigated and then applied to real sample analysis. Experimental results indicated that the MDS/SPE by using regenerated cellulose hollow fiber (8-cm length) and 1 mM sulfuric acid as the perfusate at 20 microL/min flow-rate to collect analytes from 100-fold diluted urine sample (20 mL at pH 6.0), and then having been trapped in octadecyl-modified silica phase SPE for 30 min, offered the optimum efficiency. The concentration levels of 41, 42 and 28% (m/m) for K, NK and DHNK, respectively, in urine were redeemed for determination. The detection limits were 0.38, 0.33 and 0.34 ng/mL (in 100-fold diluted sample) for K, NK and DHNK, respectively. The method provides a very simple, inexpensive and eco-friendly procedure to determine K, NK and DHNK in urine.