Dispersive liquid-liquid microextraction combined with high performance liquid chromatography-fluorescence detection for the determination of carbendazim and thiabendazole in environmental samples

A rapid and sensitive method for the determination of carbendazim (methyl benzimidazole-2-ylcarbamate, MBC) and thiabendazole (TBZ) in water and soil samples was developed by using dispersive liquid-liquid microextraction (DLLME) coupled with high performance liquid chromatography with fluorescence detection. The water samples were directly used for the DLLME extraction. For soil samples, the target analytes were first extracted by 0.1 mol L⁻¹ HCl. Then, the pH of the extract was adjusted to 7.0 with 2 mol L⁻¹ NaOH before the DLLME extraction. In the DLLME extraction method, chloroform (CHCl₃) was used as extraction solvent and tetrahydrofuran (THF) as dispersive solvent. Under the optimum conditions, the enrichment factors for MBC and TBZ were ranged between 149 and 210, and the extraction recoveries were between 50.8 and 70.9%, respectively. The linearity of the method was obtained in the range of 5-800 ng mL⁻¹ for water sample analysis, and 10-1000 ng g⁻¹ for soil samples, respectively. The correlation coefficients (r) ranged from 0.9987 to 0.9997. The limits of detection were 0.5-1.0 ng mL⁻¹ for water samples, and 1.0-1.6 ng g⁻¹ for soil samples. The relative standard deviations (RSDs) varied from 3.5 to 6.8% (n = 5). The recoveries of the method for MBC and TBZ from water samples at spiking levels of 5 and 20 ng mL⁻¹ were 84.0-94.0% and 86.0-92.5%, respectively. The recoveries for soil samples at spiking levels of 10 and 100 ng g⁻¹ varied between 82.0 and 93.4%.     

Determination of cyromazine and melamine in chicken eggs using quick,easy, cheap,effective, rugged and safe (QuEChERS) extraction coupled with liquid chromatography–tandem mass spectrometry

A rapid and sensitive method has been developed for the simultaneous detection of cyromazine and melamine in chicken eggs using the quick, easy, cheap, effective, rugged and safe (QuEChERS) method coupled with liquid chromatography–tandem mass spectrometry (LC–MS/MS). The optimal extraction solvent for the liquid–liquid extraction was 5 mL of acetonitrile with a 0.1 M hydrochloric acid aqueous solution (99.5:0.5, v/v). The extract was cleaned with 0.5 g of anhydrous magnesium sulfate and 10 mg of graphitized carbon black. The analysis of cyromazine and melamine was accomplished by combining the use of an anion exchange LC column with tandem mass spectrometry in the positive electrospray ionization mode with selected reaction monitoring mode (SRM). The detection limits were 1.6 ng g⁻¹ for cyromazine and 8 ng g⁻¹ for melamine, and the quantitation limits were 5.5 ng g⁻¹ for cyromazine and 25 ng g⁻¹ for melamine. The recoveries of cyromazine and melamine in the spiked egg samples were 83.2% and 104.6%, respectively, with an relative standard deviation (RSD) of less than 18.1%. The intra-day and inter-day precisions, represented by the RSD, ranged from 1.5% to 8.8% and 6.8% to 14.3%, respectively. The proposed method was tested by analyzing chicken eggs from the markets and from the veterinary medicine laboratory. The concentrations of cyromazine and melamine detected in these samples were in the range of 20–94 ng g⁻¹. The results demonstrated that the QuEChERS method combined with LC–MS/MS is a simple, rapid and inexpensive method for the analysis of cyromazine and melamine in eggs.     

Determination of aflatoxins in cereal flours by solid-phase microextraction coupled with liquid chromatography and post-column photochemical derivatization-fluorescence detection

A new method for the determination of aflatoxins B₁, B₂, G₁, and G₂ (AFB₁, AFB₂, AFG₁, AFG₂) in cereal flours based on solid-phase microextraction (SPME) coupled with high performance liquid chromatography with post-column photochemical derivatization and fluorescence detection (SPME–HPLC–PD–FD) has been developed. Aflatoxins were extracted from cereal flour samples by a methanol:phosphate buffer (pH 5.8, I = 0.1) (80:20, v/v) solution, followed by a SPME step. Different SPME and HPLC–PD–FD parameters (fiber polarity, temperature, pH, ionic strength, adsorption and desorption time, mobile phase) have been investigated and optimized. This method, which was assessed for the analysis of different cereal flours, showed interesting results in terms of LOD (from 0.035 to 0.2 ng g⁻¹), LOQ (from 0.1 to 0.63 ng g⁻¹, respectively), within and inter-day repeatability (2.27% and 5.38%, respectively) linear ranges (up to 20 ng g⁻¹ for AFB₁ and AFG₁ and 6 ng g⁻¹ for AFB₂ and AFG₂), and total raw extraction efficiency (in the range 55–59% at concentrations in the range 0.3–1 ng g⁻¹ and 49–52% at concentrations in the range 1–10 ng g⁻¹). The results were also compared with the purification step carried out by conventional immunoaffinity columns.     

Determination of tetrabromobisphenol-A,tetrachlorobisphenol-A and bisphenol-A in soil by ultrasonic assisted extraction and gas chromatography–mass spectrometry

In this work, an isotope dilution method for the determination, in agricultural and industrial soil samples, of tetrabromobisphenol-A, tetrachlorobisphenol-A and bisphenol-A by gas chromatography–mass spectrometry was developed. The compounds were extracted from soil by sonication assisted extraction in small columns (SAESC) with a low volume of ethyl acetate as extraction solvent. For dirty soil samples, such as industrial soils, a simultaneous clean-up on an acidified Florisil–anhydrous sodium sulfate mixture was carried out to remove interferences. After extraction, solvent was evaporated and analytes were derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and determined by isotope dilution gas chromatography with electron impact mass spectrometric detection in the selected ion monitoring mode (GC–MS–SIM), using ¹³C₁₂ labeled compounds as internal standards. Recoveries from spiked samples were between 88% and 108% and the estimated limits of detection (S/N = 3) varied from 30 pg g⁻¹ to 90 pg g⁻¹. The response obtained with this method was linear over the range assayed, 5–300 ng ml⁻¹, with correlation coefficients equal or higher than 0.999. The validated method was used to investigate the levels of these phenolic compounds in soil samples collected from different locations in Spain. Bisphenol-A was detected in all samples at concentrations from 0.7 ng g⁻¹ to 4.6 ng g⁻¹ in agricultural soils and from 1.1 ng g⁻¹ to 44.5 ng g⁻¹ in industrial soils. Tetrabromobisphenol-A was found in various soil samples at levels in the range of 3.4–32.2 ng g⁻¹ in industrial soils and at 0.3 ng g⁻¹ in one agricultural soil, whereas tetrachlorobisphenol-A was not detected.     

Electro membrane extraction of sodium diclofenac as an acidic compound from wastewater,urine, bovine milk,and plasma samples and quantification by high-performance liquid chromatography

Electro membrane extraction (EME) as a new microextraction method was applied for extraction of sodium diclofenac (SDF) as an acidic compound from wastewater, urine, bovine milk and plasma samples. Under applied potential of 20 V during the extraction, SDF migrated from a 2.1 mL of sample solution (1 mM NaOH), through a supported liquid membrane (SLM), into a 30 μL acceptor solution (10 mM NaOH), exist inside the lumen of the hollow fiber. The negative electrode was placed in the donor solution, and the positive electrode was placed in the acceptor solution. 1-octanol was immobilized in the pores of a porous hollow fiber of polypropylene as SLM. Then the extract was analyzed by means of high-performance liquid chromatography (HPLC) with UV-detection for quantification of SDF. Best results were obtained using a phosphate running electrolyte (10 mM, pH 2.5). The ranges of quantitation for different samples were 8–500 ng mL⁻¹. Intra- and inter-day RSDs were less than 14.5%. Under the optimized conditions, the preconcentration factors were between 31 and 66 and also the limit of detections (LODs) ranged from 2.7 ng mL⁻¹ to 5 ng mL⁻¹ in different samples. This procedure was applied to determine SDF in wastewater, bovine milk, urine and plasma samples (spiked and real samples). Extraction recoveries for different samples were between 44–95% after 5 min of extraction.     

Novel sponge-like molecularly imprinted mesoporous silica material for selective isolation of bisphenol A and its analogues from sediment extracts

Bisphenol A (BPA) imprinted sponge mesoporous silica was synthesized using a combination of semi-covalent molecular imprinting and simple self-assembly process. The molecularly imprinted sponge mesoporous silica (MISMS) material obtained was characterized by FT-IR, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption measurements. The results show that the MISMS possessed a large specific surface area (850.55 m² g⁻¹) and a highly interconnected 3-D porous network. As a result, the MISMS demonstrated a superior specific adsorption capacity of 169.22 μmol g⁻¹ and fast adsorption kinetics (reaching equilibrium within 3 min) for BPA. Good class selectivity for BPA and its analogues (bisphenol F, bisphenol B, bisphenol E and bisphenol AF) was also demonstrated by the sorption experiment. The MISMS as solid-phase extraction (SPE) material was then evaluated for isolation and clean-up of these bisphenols (BPs) from sediment samples. An accurate and sensitive analytical method based on the MISMS–SPE coupled with HPLC–DAD has been successfully established for simultaneous determination of five BPs in river sediments with detection limits of 0.43–0.71 ng g⁻¹ dry weight (dw). The recoveries of BPs for lyophilizated sediment samples at two spiking levels (50 and 500 ng g⁻¹ dw for each BP) were in the range of 75.5–105.5% with RSD values below 7.5%.     

Determination of commonly used azole antifungals in various waters and sewage sludge using ultra-high performance liquid chromatography–tandem mass spectrometry

Sensitive and reliable methods have been developed and validated for determination of commonly consumed azole antifungal pharmaceuticals (clotrimazole, econazole, ketoconazole, and miconazole) and biocides (propiconazole and tebuconazole) in various waters and sewage sludge. Solid phase extraction (SPE) combined with ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) was used to determine the azole antifungals in waters. Azole antifungals in sewage sludge were extracted with ultrasonic-assisted extraction, followed by SPE cleanup and UHPLC–MS/MS detection. Quantification was performed by internal standard calibration in multiple reaction monitoring mode. Recoveries were mostly in the range of 52–110% with relative standard deviations generally within 20%. Method quantification limits were 0.5–6 ng L⁻¹ in waters and 3–9 ng g⁻¹ dry weight (dw) in sewage sludge, respectively. The methods were applied to determine the azole antifungals in wastewater, river water, sediment, and sewage sludge sampled from the Pearl River Delta, China. Clotrimazole, ketoconazole, and miconazole were widely detected at low ng L⁻¹ in waters, low ng g⁻¹ dw in river sediment, and low μg g⁻¹ dw in sewage sludge. The methods can provide valuable tools for investigating occurrence and fate of the azole antifungals in the environment.     

Multi-class,multi-residue analysis of pesticides,polychlorinated biphenyls,polycyclic aromatic hydrocarbons,polybrominated diphenyl ethers and novel flame retardants in fish using fast,low-pressure gas chromatography–tandem mass spectrometry

A multi-class, multi-residue method for the analysis of 13 novel flame retardants, 18 representative pesticides, 14 polychlorinated biphenyl (PCB) congeners, 16 polycyclic aromatic hydrocarbons (PAHs), and 7 polybrominated diphenyl ether (PBDE) congeners in catfish muscle was developed and evaluated using fast low pressure gas chromatography triple quadrupole tandem mass spectrometry (LP-GC/MS–MS). The method was based on a QuEChERS (quick, easy, cheap, effective, rugged, safe) extraction with acetonitrile and dispersive solid-phase extraction (d-SPE) clean-up with zirconium-based sorbent prior to LP-GC/MS–MS analysis. The developed method was evaluated at 4 spiking levels and further validated by analysis of NIST Standard Reference Materials (SRMs) 1974B and 1947. Sample preparation for a batch of 10 homogenized samples took about 1 h/analyst, and LP-GC/MS–MS analysis provided fast separation of multiple analytes within 9 min achieving high throughput. With the use of isotopically labeled internal standards, recoveries of all but one analyte were between 70 and 120% with relative standard deviations less than 20% (n = 5). The measured values for both SRMs agreed with certified/reference values (72–119% accuracy) for the majority of analytes. The detection limits were 0.1–0.5 ng g⁻¹ for PCBs, 0.5–10 ng g⁻¹ for PBDEs, 0.5–5 ng g⁻¹ for select pesticides and PAHs and 1–10 ng g⁻¹ for flame retardants. The developed method was successfully applied for analysis of catfish samples from the market.     

Ultrasound-assisted surfactant-enhanced emulsification microextraction for the determination of carbamate pesticides in water samples by high performance liquid chromatography

A novel ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) coupled with high performance liquid chromatography-diode array detection has been developed for the extraction and determination of six carbamate pesticides (metolcarb, carbofuran, carbaryl, pirimicarb, isoprocarb and diethofencarb) in water samples. In the UASEME technique, Tween 20 was used as emulsifier, and chlorobenzene and chloroform were used as dual extraction solvent without using any organic dispersive solvent that is normally required in the previously described common dispersive liquid–liquid microextraction method. Parameters that affect the extraction efficiency, such as the kind and volume of the extraction solvent, the type and concentration of the surfactant, ultrasound emulsification time and salt addition, were investigated and optimized for the method. Under the optimum conditions, the enrichment factors were in the range between 170 and 246. The limits of detection of the method were 0.1–0.3 ng mL⁻¹ and the limits of quantification were between 0.3 and 0.9 ng mL⁻¹, depending on the compounds. The linearity of the method was obtained in the range of 0.3–200 ng mL⁻¹ for metolcarb, carbaryl, pirimicarb, and diethofencarb, 0.6–200 ng mL⁻¹ for carbofuran, and 0.9–200 ng mL⁻¹ for isoprocarb, with the correlation coefficients (r) ranging from 0.9982 to 0.9998. The relative standard deviations varied from 3.2 to 4.8% (n = 5). The recoveries of the method for the six carbamates from water samples at spiking levels of 1.0, 10.0, 50.0 and 100.0 ng mL⁻¹ were ranged from 81.0 to 97.5%. The proposed UASEME technique has demonstrated to be simple, practical and environmentally friendly for the determination of carbamates residues in river, reservoir and well water samples.     

High-performance liquid chromatography with fluorescence detection and ultra-performance liquid chromatography with electrospray tandem mass spectrometry method for the determination of indoleamine neurotransmitters and their metabolites in sea lamprey plasma

We present a comparison of two sensitive methods, HPLC with fluorescence detector (HPLC/FLD) and UPLC with electrospray tandem mass spectrometry (UPLC/MS/MS), for the determination of indoleamine neurotransmitters (NTs) and their metabolites in sea lamprey plasma samples. Liquid–liquid extraction (LLE) and solid-phase extraction (SPE) were also tested for recovery and matrix effect. The recoveries of SPE determined by HPLC/FLD and UPLC/MS/MS ranged from 75 to 123% and 78 to 105%, respectively, while the recoveries of LLE ranged from 45 to 73% and 48 to 75%, respectively. SPE combined with HPLC/FLD and UPLC/MS/MS to determine the target analytes in plasma samples were validated of the sensitivity, reproducibility, accuracy and precision. Both methods exhibited excellent linearity in the range of 0.2–50 ng mL⁻¹ for all analytes. The limits of detection (LOD) varied from 0.04 ng mL⁻¹ to 0.13 ng mL⁻¹ for HPLC/FLD method and 0.003 ng mL⁻¹ to 0.02 ng mL⁻¹ for UPLC/MS/MS method. The inter-day accuracy ranged from 82.5 to 127.0% for HPLC/FLD and 93.0 to 113.0% for UPLC/MS/MS. The inter-day precision ranged from 9.9 to 32.3% for HPLC/FLD and 5.4 to 13.2% for UPLC/MS/MS. These results demonstrated that the values obtained by both methods were within the satisfactory range and the UPLC/MS/MS method provided more accurate and precise measurements than HPLC/FLD method. The comparison is of great importance to determine the available detectors, considering the complexity and expensiveness versus quality parameters. These two methods were applied to the analysis of four important indoleamine neurotransmitter analytes (5-hydroxytryptamine, 5-hydroxyindole-3-acetic acid, tryptamine and melatonin) in sea lamprey plasma samples.     

Analysis of intracellular and extracellular microcystin variants in sediments and pore waters by accelerated solvent extraction and high performance liquid chromatography-tandem mass spectrometry

The fate and persistence of microcystin cyanotoxins in aquatic ecosystems remains poorly understood in part due to the lack of analytical methods for microcystins in sediments. Existing methods have been limited to the extraction of a few extracellular microcystins of similar chemistry. We developed a single analytical method, consisting of accelerated solvent extraction, hydrophilic–lipophilic balance solid phase extraction, and reversed phase high performance liquid chromatography-tandem mass spectrometry, suitable for the extraction and quantitation of both intracellular and extracellular cyanotoxins in sediments as well as pore waters. Recoveries of nine microcystins, representing the chemical diversity of microcystins, and nodularin (a marine analogue) ranged between 75 and 98% with one, microcystin-RR (MC-RR), at 50%. Chromatographic separation of these analytes was achieved within 7.5 min and the method detection limits were between 1.1 and 2.5 ng g⁻¹ dry weight (dw). The robustness of the method was demonstrated on sediment cores collected from seven Canadian lakes of diverse geography and trophic states. Individual microcystin variants reached a maximum concentration of 829 ng g⁻¹ dw on sediment particles and 132 ng mL⁻¹ in pore waters and could be detected in sediments as deep as 41 cm (>100 years in age). MC-LR, -RR, and -LA were more often detected while MC-YR, -LY, -LF, and -LW were less common. The analytical method enabled us to estimate sediment-pore water distribution coefficients (K_d), MC-RR had the highest affinity for sediment particles (log K_d = 1.3) while MC-LA had the lowest affinity (log K_d = −0.4), partitioning mainly into pore waters. Our findings confirm that sediments serve as a reservoir for microcystins but suggest that some variants may diffuse into overlying water thereby constituting a new route of exposure following the dissipation of toxic blooms. The method is well suited to determine the fate and persistence of different microcystins in aquatic systems.     

Development of an analytical methodology for the determination of the antiparasitic drug toltrazuril and its two metabolites in surface water,soil and animal manure

This paper presents the development, optimization and validation of a LC–MS/MS methodology to determine the antiparasitic veterinary drug toltrazuril and its two main metabolites, toltrazuril sulfoxide and toltrazuril sulfone, in environmental surface water, soil and animal manure. Using solid phase extraction and selective pressurized liquid extraction with integrated clean-up, the analytical method allows for the determination of these compounds down to 0.06–0.13 ng L⁻¹ in water, 0.01–0.03 ng g⁻¹ dw in soil and 0.22–0.51 ng g⁻¹ dw in manure. The deuterated analog of toltrazuril was used as internal standard, and ensured method accuracy in the range 96–123% for water and 77–110% for soil samples. The developed method can also be applied to simultaneously determine steroid hormones in the solid samples. The antiparasitic drug and its metabolites were found in manure and soil up to 114 and 335 pg g⁻¹ dw, respectively. Little is known regarding the environmental fate and effects of these compounds; consequently more research is urgently needed.     

On-line coupling of dynamic microwave-assisted extraction to solid-phase extraction for the determination of sulfonamide antibiotics in soil

A rapid technique based on dynamic microwave-assisted extraction (DMAE) coupled on-line with solid-phase extraction (SPE) was developed for the determination of sulfonamides (SAs) including sulfadiazine, sulfameter, sulfamonomethoxine and sulfaquinoxaline in soil. The SAs were first extracted with acetonitrile under the action of microwave energy, and then directly introduced into the SPE column which was packed with neutral alumina for preconcentration of analytes and clean-up of sample matrix. Subsequently, the SAs trapped on the alumina were eluted with 0.3% acetic acid aqueous solution and determined by liquid chromatography-tandem mass spectrometry. The DMAE parameters were optimized by the Box-Behnken design. Maximum extraction efficiency was achieved using 320 W of microwave power; 12 mL of extraction solvent and 0.8 mL min⁻¹ of extraction solvent flow rate. The limits of detection and quantification obtained are in the range of 1.4-4.8 ng g⁻¹ and 4.6-16.0 ng g⁻¹ for the SAs, respectively. The mean values of relative standard deviation of intra- and inter-day ranging from 2.7% to 5.3% and from 5.6% to 6.7% are obtained, respectively. The recoveries of SAs obtained by analyzing four spiked soil samples at three fortified levels (20 ng g⁻¹, 100 ng g⁻¹ and 500 ng g⁻¹) were from 82.6 ± 6.0% to 93.7 ± 5.5%. The effect of standing time of spiked soil sample on the SAs recoveries was examined. The recoveries of SAs decreased from (86.3-101.9)% to (37.6-47.5)% when the standing time changed from one day to four weeks.     

Coacervative microextraction ultrasound-assisted back-extraction technique for determination of organophosphates pesticides in honey samples by gas chromatography–mass spectrometry

Coacervative microextraction ultrasound-assisted back-extraction technique (CME-UABE) is proposed for the first time for extracting and preconcentrating organophosphates pesticides (OPPs) from honey samples prior to gas chromatography–mass spectrometry (GC–MS) analysis. The extraction/preconcentration technique is supported on the micellar organized medium based on non-ionic surfactant. To enable coupling the proposed technique with GC, it was required to back extract the analytes into hexane. Several variables including, surfactant type and concentration, equilibration temperature and time, matrix modifiers, pH and buffers nature were studied and optimized over the relative response of the analytes. The best working conditions were as follows: an aliquot of 10 mL 50 g L⁻¹ honey blend solution was conditioned by adding 100 μL 0.1 mol L⁻¹ hydrochloric acid (pH 2) and finally extracted with 100 μL Triton X-114 100 g L⁻¹ at 85 °C for 5 min using CME technique. Under optimal experimental conditions, the enrichment factor (EF) was 167 and limits of detection (LODs), calculated as three times the signal-to-noise ratio (S/N = 3), ranged between 0.03 and 0.47 ng g⁻¹. The method precision was evaluated over five replicates at 1 ng g⁻¹ with RSDs ≤9.5%. The calibration graphs were linear within the concentration range of 0.3–1000 ng g⁻¹ for chlorpirifos; and 1–1000 ng g⁻¹ for fenitrothion, parathion and methidathion, respectively. The coefficients of correlation were ≥0.9992. Validation of the methodology was performed by standard addition method at two concentration levels (2 and 20 ng g⁻¹). The recoveries were ≥90%, indicating satisfactory robustness of the methodology, which could be successfully applied for determination of OPPs in honey samples of different Argentinean regions. Two of the analyzed samples showed levels of methidathion ranged between 1.2 and 2.3 ng g⁻¹.     

Determination of carbamate pesticides using micro-solid-phase extraction combined with high-performance liquid chromatography

We describe a simple and sensitive porous polypropylene membrane-protected micro-solid-phase extraction (μ-SPE) approach for the sample preparation and determination of carbamate pesticides in soil samples by high-performance liquid chromatography. The μ-SPE device consisted of C₁₈ sorbent held within a porous polypropylene envelope. In order to achieve optimum performance, several extraction parameters were optimized. Under the most favorable conditions, the extraction efficiency of the μ-SPE was very high, with detection limits in the range of 0.01–0.40 ng g⁻¹. This is more than two orders of magnitude lower than the limits obtained by the United States Environmental Protection Agency Methods 8321A and 8318. A linear relationship was obtained for each analyte in the range of 2 and 200 ng g⁻¹. The relative standard deviation for the analysis of aged soil samples spiked at 5 ng g⁻¹ was ≤11%. The reproducibility of separate μ-SPE device used for experiments was satisfactory (relative standard deviations ranged from 4 to 11%), indicating that the method is reliable for routine environmental analysis.     

Dispersive solid-phase extraction followed by dispersive liquid–liquid microextraction for the determination of some sulfonylurea herbicides in soil by high-performance liquid chromatography

Dispersive solid-phase extraction (DSPE) combined with dispersive liquid–liquid microextraction (DLLME) has been developed as a new approach for the extraction of four sulfonylurea herbicides (metsulfuron-methyl, chlorsulfuron, bensulfuron-methyl and chlorimuron-ethyl) in soil prior to high-performance liquid chromatography with diode array detection (HPLC-DAD). In the DSPE-DLLME, sulfonylurea herbicides were first extracted from soil sample into acetone–0.15 mol L⁻¹ NaHCO₃ (2:8, v/v). The clean-up of the extract by DSPE was carried out by directly adding C₁₈ sorbent into the extract solution, followed by shaking and filtration. After the pH of the filtrate was adjusted to 2.0 with 2 mol L⁻¹ HCl, 60.0 μL chlorobenzene (as extraction solvent) was added into 5.0 mL of it for DLLME procedure (the acetone contained in the solution also acted as dispersive solvent). Under the optimum conditions, the enrichment factors for the compounds were in the range between 102 and 216. The linearity of the method was in the range from 5.0 to 200 ng g⁻¹ with the correlation coefficients (r) ranging from 0.9967 to 0.9987. The method detection limits were 0.5–1.2 ng g⁻¹. The relative standard deviations varied from 5.2% to 7.2% (n = 5). The relative recoveries of the four sulfonylurea herbicides from soil samples at spiking levels of 6.0, 20.0 and 60.0 ng g⁻¹ were in the range between 76.3% and 92.5%. The proposed method has been successfully applied to the analysis of the four target sulfonylurea herbicides in soil samples, and a satisfactory result was obtained.     

Development and validation of a liquid chromatography–tandem mass spectrometry assay for the simultaneous quantitation of microcystin-RR and its metabolites in fish liver

A novel method for identification and quantification of microcystin-RR (MC-RR) and its metabolites (MC-RR-GSH and MC-RR-Cys) in the fish liver was developed and validated. These analytes were simultaneously extracted from fish liver using water containing EDTA with 5% acetic acid, followed by a mixed-mode cation-exchange SPE (Oasis MCX) and subsequently determined by liquid chromatography–electrospray ionization ion trap mass spectrometry (LC–ESI-ITMS). Extraction parameters including volume and pH of eluting solvents, were optimized. Best recoveries were obtained by using 10 mL of 15% ammonia solution in methanol. The mean recoveries at three concentrations (0.2, 1.0, and 5.0 μg g⁻¹ dry weight [DW]) for MC-RR, MC-RR-GSH and MC-RR-Cys were 93.6–99%, 68.1–73.6% and 90.0–95.2%, respectively. Method detection limit (MDL) were 4, 7 and 5 ng g⁻¹ DW for MC-RR, MC-RR-GSH and MC-RR-Cys, respectively. Limits of quantification (LOQs) for MC-RR, MC-RR-GSH and MC-RR-Cys were calculated to be 10, 18 and 13 ng g⁻¹ DW, respectively. Finally, this method was successfully applied to the identification and quantification of MC-RR, MC-RR-GSH and MC-RR-Cys in the liver of bighead carp with acute exposure of MCs.     

A highly sensitive and selective immunoassay for the detection of tetrabromobisphenol A in soil and sediment

Tetrabromobisphenol A is the most widely used brominated flame retardant. A sensitive and selective enzyme-linked immunosorbent assay (ELISA) for the detection of tetrabromobisphenol A was developed. The limit of detection and the inhibition half-maximum concentration of tetrabromobisphenol A in phosphate buffered saline with 10% methanol were 0.05 and 0.87 ng mL⁻¹, respectively. Cross-reactivity values of the ELISA with a set of important brominated flame retardants including tetrabromobisphenol A-bis(2,3-dibromopropylether), 2,2′,6,6′-tetrabromobisphenol A diallyl ether, hexabromocyclododecane, 1,2-bis(pentabromodiphenyl) ethane, 1,2-bis(2,4,6 tribromophenoxy) ethane, bis(2-ethylhexyl)-3,4,5,6-tetrabromophthalate, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate, and polybrominated diphenyl ethers were <0.05%. Concentrations of tetrabromobisphenol A determined by ELISA in the soils from farmlands, the soils from an e-waste recycling site, and the sediments of a canal were in the range of non-detectable–5.6 ng g⁻¹, 26–104 ng g⁻¹ and 0.3–22 ng g⁻¹ dw, respectively, indicating the ubiquitous pollution of tetrabromobisphenol A. The results of this assay for 16 real world samples agreed well with those of the liquid chromatography–tandem mass spectrometry method, indicating this ELISA is suitable for screening of tetrabromobisphenol A in environmental matrices.     

Quantification of human pharmaceuticals in water samples by high performance liquid chromatography-tandem mass spectrometry

An improved analytical method for determination of human pharmaceuticals in natural and wastewaters with ng L⁻¹ sensitivity is presented. The method is applicable to pharmaceuticals from a wide range of therapeutic classes including antibiotics, analgesics, anti-inflammatories and anti-cancer compounds. Pharmaceuticals were extracted from waters using solid-phase extraction, and after concentration, analysed by high performance liquid chromatography with tandem mass spectrometric detection (HPLC-MS/MS). Identification of each compound was secured using retention time and by the selected reaction monitoring of two transitions, one of which was additionally used for quantification. Limits of detection ranged from 0.03 to 0.96 ng L⁻¹ and were up to two orders of magnitude lower than those of previously published methods. The method was validated using spiked samples prepared from tap, river and sea water as well as wastewater effluents, collected from the North of Scotland. Analysis of wastewater effluents revealed the presence of mefenamic acid, ibuprofen, erythromycin, diclofenac and trimethoprim. None of the selected pharmaceuticals were detected in river, tap or sea water samples.     

Determination of 13 endocrine disrupting chemicals in sediments by gas chromatography–mass spectrometry using subcritical water extraction coupled with dispersed liquid–liquid microextraction and derivatization

In this study, a sample pretreatment method was developed for the determination of 13 endocrine disrupting chemicals (EDCs) in sediment samples based on the combination of subcritical water extraction (SWE) and dispersed liquid–liquid microextraction (DLLME). The subcritical water that provided by accelerated solvent extractor (ASE) was the sample solution (water) for the following DLLME and the soluble organic modifier that spiked in the subcritical water was also used as the disperser solvent for DLLME in succession. Thus, several important parameters that affected both SWE and DLLME were investigated, such as the extraction solvent for DLLME (chlorobenzene), extraction time for DLLME (30 s), selection of organic modifier for SWE (acetone), volume of organic modifier (10%) and extraction temperature for SWE (150 °C). In addition, good chromatographic behavior was achieved for GC–MS after derivatisation by using N,O-bis(trimethylsilyl) trifluoroacetamide (BSTFA). As a result, proposed method sensitive and reliable with the limits of detection (LODs) ranging from 0.006 ng g⁻¹ (BPA) to 0.639 ng g⁻¹ (19-norethisterone) and the relative standard deviations (RSDs) between 1.5% (E2) and 15.0% (DES). Moreover, the proposed method was compared with direct ASE extraction that reported previously, and the results showed that SWE–DLLME was more promising with recoveries ranging from 42.3% (dienestrol) to 131.3% (4,5α-dihydrotestosterone), except for diethylstilbestrol (15.0%) and nonylphenols (29.8%). The proposed method was then successfully applied to determine 13 EDCs sediment of Humen outlet of the Pearl River, 12 of target compounds could be detected, and 10 could be quantitative analysis with the total concentration being 39.6 ng g⁻¹, and which indicated that the sediment of Humen outlet was heavily contaminated by EDCs.