Evaluation of a new method for chemical coating of aluminum wire with molecularly imprinted polymer layer. Application for the fabrication of triazines selective solid-phase microextraction fiber

A new solid-phase microextraction (SPME) fiber is fabricated through ultra violet irradiation polymerization of ametryn-molecularly imprinted polymer on the surface of anodized-silylated aluminum wire. The prepared fiber is durable with very good chemical and thermal stability which can be coupled to GC and GC/MS. The effective parameters on the fabrication and application procedures such as spraying mode, ultra violet irradiation (polymerization) time, number of sprayings and polymerizations, pH and ionic strength of sample and extraction time were optimized. This fiber shows high selectivity with great extraction capacity toward triazines. SPME and GC analysis of ametryn, prometryn, terbutryn, atrazine, simazine, propazine and cyanazine using the fabricated fiber result in the detection limits of 9, 32, 27, 43, 51, 74 and 85 ng mL⁻¹, respectively. The reliability of the prepared fiber in real samples has been investigated and proved by using spiked tap water, rice, maize and onion samples.     

Headspace solid-phase microextraction using a dodecylsulfate-doped polypyrrole film coupled to ion mobility spectrometry for the simultaneous determination of atrazine and ametryn in soil and water samples

A simple and rapid headspace solid-phase microextraction (HS-SPME) based method is presented for the simultaneous determination of atrazine and ametryn in soil and water samples by ion mobility spectrometry (IMS). A dodecylsulfate-doped polypyrrole (PPy-DS), synthesized by electrochemical method, was applied as a laboratory-made fiber for SPME. The HS-SPME system was designed with a cooling device on the upper part of the sample vial and a circulating water bath for adjusting the sample temperature. The extraction properties of the fiber to spiked soil and water samples with atrazine and ametryn were examined, using a HS-SPME device and thermal desorption in injection port of IMS. Parameters affecting the extraction efficiency such as the volume of water added to the soil, pH effect, extraction time, extraction temperature, salt effect, desorption time, and desorption temperature were investigated. The HS-SPME-IMS method with PPy-DS fiber, provided good repeatability (RSDs < 10 %), simplicity, good sensitivity and short analysis times for spiked soil (200 ng g⁻¹) and water samples (100 and 200 ng mL⁻¹). The calibration graphs were linear in the range of 200-4000 ng g⁻¹ and 50-2800 ng mL⁻¹ for soil and water respectively (R² > 0.99). Detection limits for atrazine and ametryn were 37 ng g⁻¹ (soil) and 23 ng g⁻¹ (soil) and 15 ng mL⁻¹ (water) and 10 ng mL⁻¹ (water), respectively. To evaluate the accuracy of the proposed method, atrazine and ametryn in the three kinds of soils and two well water samples were determined. Finally, comparing the HS-SPME results for extraction and determination of selected triazines using PPy-DS fiber with the other methods in literature shows that the proposed method has comparable detection limits and RSDs and good linear ranges.     

Evaluation of a completely automated cold fiber device using compounds with varying volatility and polarity

A fully automated cold fiber solid phase microextraction device has been developed by coupling to a GERSTEL multipurpose (MPS 2) autosampler and applied to the analysis of volatiles and semi-volatiles in aqueous and solid matrices. The proposed device was thoroughly evaluated for its extraction performance, robustness, reproducibility and reliability by gas chromatograph/mass spectrometer (GC/MS). With the use of a septumless head injector, the entire automated setup was capable of analyzing over 200 samples without any GC injector leakages. Evaluation of the automated cold fiber device was carried out using a group of compounds characterized by different volatilities and polarities. Extraction efficiency as well as analytical figures of merit was compared to commercial solid phase microextraction fibers. The automated cold fiber device showed significantly improved extraction efficiency compared to the commercial polydimethylsiloxane (PDMS) and cold fiber without cooling for the analysis of aqueous standard samples due to the low temperature of the coating. Comparing results obtained from cold fiber and commercial divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber temperature profile demonstrated that the temperature gap between the sample matrix and the coating improved the distribution coefficient and therefore the extraction amount. The linear dynamic range of the cold fiber device was 0.5 ng mL⁻¹ to 100 ng mL⁻¹ with a linear regression coefficient ≥0.9963 for all compounds. The limit of detection for all analytes ranged from 1.0 ng mL⁻¹ to 9.4 ng mL⁻¹. The newly automated cold fiber device presents a platform for headspace analysis of volatiles and semi-volatiles for large number of samples with improved throughput and sensitivity.     

Metal-organic framework-templated synthesis of magnetic nanoporous carbon as an efficient absorbent for enrichment of phenylurea herbicides

Nanoporous carbon with a high specific surface area and unique porous structure represents an attractive material as an adsorbent in analytical chemistry. In this study, a magnetic nanoporous carbon (MNC) was fabricated by direct carbonization of Co-based metal-organic framework in nitrogen atmosphere without using any additional carbon precursors. The MNC was used as an effective magnetic adsorbent for the extraction and enrichment of some phenylurea herbicides (monuron, isoproturon, diuron and buturon) in grape and bitter gourd samples prior to their determination by high performance liquid chromatography with ultraviolet detection. Several important experimental parameters that could influence the extraction efficiency were investigated and optimized. Under the optimum conditions, a good linearity was achieved in the concentration range of 1.0–100.0 ng g⁻¹ for monuron, diuron and buturon and 1.5–100.0 ng g⁻¹ for isoproturon with the correlation coefficients (r) larger than 0.9964. The limits of detection (S/N = 3) of the method were in the range from 0.17 to 0.46 ng g⁻¹. The results indicated that the MNC material was stable and efficient adsorbent for the magnetic solid-phase extraction of phenylurea herbicides and would have a great application potential for the extraction and preconcentration of more organic pollutants from real samples.     

Analysis of chloroacetanilide herbicides in water samples by solid-phase microextraction coupled with gas chromatography-mass spectrometry

A solid-phase microextraction (SPME) method has been developed for the determination of 3 chloroacetanilide herbicides in both fresh and seawater samples. The extracted sample was analyzed by gas chromatography with mass spectrometry detection (GC-MS), and parameters affecting SPME operation including fibre type, sample pH, sample temperature, mixing speed and extraction time have been evaluated and optimized. The amount of dissolved organic matter (DOM) and the salt content both affected SPME extraction efficiency, but the presence of other competitive extractants such as organochlorine pesticides (OCPs) in the matrix showed no insignificance interference. The limit of detection (LOD) for acetochlor, metolachlor and butachlor were 1.2, 1.6 and 2.7 ng L⁻¹, respectively. The recoveries for the herbicides ranged from 79 to 102%, and the linear dynamic range was from 10 to 1000 ng L⁻¹. The developed method has been used to monitor herbicides contaminations in coastal water samples collected around Laizhou bay and Jiaozhou bay in Shandong peninsula, China. The concentrations of acetochlor and metolachlor ranged from undetectable to 78.5 ng L⁻¹ and undetectable to 35.6 ng L⁻¹, respectively. Butachlor was not observed but in only one sample and the concentration is lower than the limit of quantification (LOQ). The concentrations of the three herbicides in this study are low compared to most of the other places reported.     

Growth of cedar-like Au nanoparticles coating on an etched stainless steel wire and its application for selective solid-phase microextraction

A novel cedar-like Au nanoparticles (AuNPs) coating was fabricated on an etched stainless steel (SS) wire by direct chemical deposition and used as an efficient and unbreakable solid phase microextraction (SPME) fiber. The etched SS wire offers a rough surface structure for subsequent growth of AuNPs in chloroauric acid solution. As a result, the uniform cedar-like AuNPs coating with larger surface area was tightly attached to the etched SS wire substrate. The AuNPs coated etched SS fiber (AuNPs/SS) was examined for SPME of ultraviolet (UV) filters, phthalate esters and aromatic hydrocarbons coupled to high-performance liquid chromatography with UV detection. The fabricated fiber exclusively exhibited excellent extraction efficiency and selectivity for some aromatic hydrocarbons. Influential parameters of extraction and desorption time, temperature, stirring rate and ionic strength were investigated and optimized. The limits of detection ranged from 0.008 μg L⁻¹ to 0.037 μg L⁻¹. The single fiber repeatability varied from 3.90% to 4.50% and the fiber-to-fiber reproducibility ranged from 5.15% to 6.87%. The recovery of aromatic hydrocarbons in real water samples spiked at 2.0 μg L⁻¹ and 20 μg L⁻¹ ranged from 94.38% to 106.2% with the relative standard deviations below 6.44%. Furthermore the growth of the cedar-like AuNPs coating can be performed in a highly reproducible manner. This fabricated fiber exhibits good stability and withstands at least 200 extraction and desorption replicates.     

HPLC-UV and HPLC-MSn multiresidue determination of amidosulfuron, azimsulfuron, nicosulfuron, rimsulfuron, thifensulfuron methyl, tribenuron methyl and azoxystrobin in surface waters

The paper presents a new HPLC method, with UV and MSⁿ detection, for the determination of seven pesticides, including the sulfonylurea herbicides amidosulfuron, azimsulfuron, nicosulfuron, rimsulfuron, thifensulfuron methyl, tribenuron methyl, and the fungicide azoxystrobin characterised by a methoxyacrilate structure. The methodology consists of a preconcentration/SPE (solid phase extraction) step and HPLC-UV (240 nm detection wavelength)-MSⁿ analysis. Under the optimised conditions and after a 1000/1 preconcentration factor, the limits of detection were lower than 14.5 ng L⁻¹ for UV detection and lower than 8.1 ng L⁻¹ for MS detection. The limits of quantification were lower than 48.3 ng L⁻¹ in UV detection and than 26.9 ng L⁻¹ in MSⁿ detection. The analysis of two samples, spiked with a mixture of the pesticides at threshold level concentrations, gave more than 60% recovery.     

Method for determination of fatty acid amides in polyethylene packaging materials—Gas chromatography/mass spectrometry

A new method for determination of fatty acid amides in polyethylene packaging film was developed using gas chromatography/mass spectrometry (GC/MS). Liquid extraction, Soxhlet extraction ultrasonic-assisted extraction and pressurized solvent extraction (PSE) methods were compared and the results showed that pressurized solvent extraction was the best for extracting these compounds. After extraction, solvent was blown by nitrogen and a trifluoroethyl derivation step was carried out. The derivative compounds were identified and quantified by GC/MS using an HP-Innowax column. The retention times were 6.20 min for derivative hexadecanoamide, 8.56 min for derivative octadecanamide, 8.84 min for derivative oleamide and 13.68 min for derivative erucamide, respectively. The detection limits were 61.0 ng g⁻¹, 74.0 ng g⁻¹, 103.0 ng g⁻¹, and 105.0 ng g⁻¹, respectively, and the linearity were good. The proposed method was applied satisfactorily to determine these chemicals in different types of polyethylene samples.     

A novel TiO2 nanotube array/Ti wire incorporated solid-phase microextraction fiber with high strength,efficiency and selectivity

A novel solid-phase microextraction (SPME) fiber is fabricated through the anodization of Ti wire substrates in an electrolyte containing ethylene glycol and NH₄F. By a combination of field emission scanning electron microscope and X-ray photoelectron spectroscope studies, it is shown that perpendicularly orientated and well-aligned TiO₂ nanotubes are grown in situ on the Ti wire substrate. The SPME fiber coupled with gas chromatograph (GC) is then used to extract polycyclic aromatic hydrocarbons (PAHs), anilines, phenols, and alkanes from standard and real water samples, and exhibits high selectivity for PAHs. After the optimization of adsorption factors (pH, ionic strength, time and temperature) and desorption factors (time and temperature) of the SPME fiber for PAHs, the limit of detection (LOD) of less than 0.1 μg L⁻¹ is achieved, and the calibration curves are all linear (R² ≥ 0.9898) in the range from 0.1 to 1000 μg L⁻¹. Beyond that, the SPME fiber has high strength, large surface area, good stability at high temperature and in acid and alkali solutions, and long service life, making it have strong application potentials in the selective extraction of PAHs from complex samples at trace levels.     

Attachment of nickel hexacyanoferrates nanoparticles on carbon nanotubes: preparation, characterization and bioapplication

Anilinemethyltriethoxysilane (AMTEOS) was first used as precursor as well as selective stationary phase to prepare the sol-gel derived anilinemethyltriethoxysilane/polydimethylsiloxane (AMTEOS/PDMS) solid-phase microextraction (SPME) fibers. The novel SPME fiber exhibits high extraction efficiency, good thermal stability and long lifetime compared with commercial SPME coatings. In addition, the phenyl groups in the porous layer can exhibit π-π interactions with aromatic compounds, such as monocyclic aromatic hydrocarbons (MAHs) and polycyclic aromatic hydrocarbons (PAHs). Therefore, SPME using the AMTEOS/PDMS sol-gel fiber coupled with GC-FID was recommended as a sensitive and selective method towards the analysis of these compounds in environmental water samples. The optimal extraction conditions were investigated by adjusting extraction time, salt addition, extraction temperature, and desorption time. The method showed linearity between 2 and 4000 μg l⁻¹ for MAHs and 1 and 1000 μg l⁻¹ for PAHs. The limit of detection (LOD) was 0.6-3.8 μg l⁻¹for MAHs and 0.2-1.5 μg l⁻¹ for PAHs. The novel AMTEOS/PDMS fiber was applied to extract small amount of aromatic compounds in wastewater and river water respectively. The recovery of the method was acceptable for quantitative analysis.     

Simultaneous UV and electrochemical determination of the herbicide asulam in tap water samples by micellar electrokinetic capillary chromatography

A simple end-column electrochemical detector was designed and attached to an available commercial capillary electrophoresis instrument with UV detection to detect different kind of herbicides and to determinate methyl-4-aminophenyl-sulfonylcarbamate (asulam) in water samples. The designed cell is very easy to assemble and disassemble in a short period of time; the working electrode positioning is also quickly achieved without micropositioners. The alignment between working electrode and capillary outlet was very reproducible for the all checked electrodes; the R.S.D. obtained was lower than 6.0% for 100 μm gap distance. In this mode, the non-electroactive and electroactive compounds could be detected by UV and electrochemical detection, respectively at the same time. The electrochemical determination of asulam using micellar electrokinetic capillary chromatography (MEKC) is the first time that is reported. In both detection systems, a linear range was obtained for asulam concentrations lower than 25.0 mg l⁻¹, in boric acid 0.020 mol l⁻¹ at pH 8.20 and containing 0.025 mol l⁻¹ of sodium dodecyl sulfate, to obtain selectivity additional separation by the micellar distribution process. Under these conditions, an experimental detection limit of 0.4 mg l⁻¹ was achieved. A new experimental scheme is also described for asulam determination in tap waters with a previous preconcentration step. Using both, UV and electrochemical detection, with a previous extraction procedure, the detection limits of asulam in tap water samples were of 1.0 and 0.8 μg l⁻¹, respectively.     

High extraction efficiency for polar aromatic compounds in natural water samples using multiwalled carbon nanotubes/Nafion solid-phase microextraction coating

A novel solid-phase microextraction (SPME) fiber coated with multiwalled carbon nanotubes (MWCNTs)/Nafion was developed and applied for the extraction of polar aromatic compounds (PACs) in natural water samples. The characteristics and the application of this fiber were investigated. Electron microscope photographs indicated that the MWCNTs/Nafion coating with average thickness of 12.5 μm was homogeneous and porous. The MWCNTs/Nafion coated fiber exhibited higher extraction efficiency towards polar aromatic compounds compared to an 85 μm commercial PA fiber. SPME experimental conditions, such as fiber coating, extraction time, stirring rate, desorption temperature and desorption time, were optimized in order to improve the extraction efficiency. The calibration curves were linear from 0.01 to 10 μg mL⁻¹ for five PACs studied except p-nitroaniline (from 0.005 to 10 μg mL⁻¹) and m-cresol (from 0.001 to 10 μg mL⁻¹), and detection limits were within the range of 0.03–0.57 ng mL⁻¹. Single fiber and fiber-to-fiber reproducibility were less than 7.5 (n = 7) and 10.0% (n = 5), respectively. The recovery of the PACs spiked in natural water samples at 1 μg mL⁻¹ ranged from 83.3 to 106.0%.     

Preparation and characterization of metal-organic framework MIL-101(Cr)-coated solid-phase microextraction fiber

Metal-organic frameworks (MOFs) have received great attention as novel sorbents due to their fascinating structures and intriguing potential applications in various fields. In this work, a MIL-101(Cr)-coated solid-phase microextraction (SPME) fiber was fabricated by a simple direct coating method and applied to the determination of volatile compounds (BTEX, benzene, toluene, ethylbenzene, m-xylene and o-xylene) and semi-volatile compounds (PAHs, polycyclic aromatic hydrocarbons) from water samples. The extraction and desorption conditions of headspace SPME (HS-SPME) were optimized. Under the optimized conditions, the established methods exhibited excellent extraction performance. Good precision (<7.7%) and low detection limits (0.32–1.7 ng L⁻¹ and 0.12–2.1 ng L⁻¹ for BTEX and PAHs, respectively) were achieved. In addition, the MIL-101(Cr)-coated fiber possessed good thermal stability, and the fiber can be reused over 150 times. The fiber was successfully applied to the analysis of BTEX and PAHs in river water by coupling with gas chromatography–mass spectrometry (GC–MS). The analytes at low concentrations (1.7 and 10 ng L⁻¹) were detected, and the recoveries obtained with the spiked river water samples were in the range of 80.0–113% and 84.8–106% for BTEX and PAHs, respectively, which demonstrated the applicability of the self-made fiber.     

Preparation of ionic liquid based solid-phase microextraction fiber and its application to forensic determination of methamphetamine and amphetamine in human urine

A new solid-phase microextraction (SPME) procedure using an ionic liquid (IL) has been developed. Reusable IL-based SPME fiber was prepared for the first time by fixing IL through cross-linkage of IL impregnated silicone elastomer on the surface of a fused silica fiber. 1-Ethoxyethyl-3-methylimidazloium bis(trifluoromethane) sulfonylimide ([EeMim][NTf₂]) ionic liquid was employed as a demonstration and the prepared fiber was applied to the forensic headspace determination of methamphetamine (MAP) and amphetamine (AP) in human urine samples. Important extraction parameters including the concentration of salt and base in sample matrix, extraction temperature and extraction time were investigated and optimized. Combined with gas chromatography/mass spectrometry (GC/MS) working in selected ion monitoring (SIM) mode, the new method showed good linearity in the range of 20–1500 μg L⁻¹, good repeatability (RSD < 7.5% for MAP, and <11.5% for AP, n = 6), and low detection limits (0.1 μg L⁻¹ for MAP and 0.5 μg L⁻¹ for AP). Feasibility of the method was evaluated by analyzing human urine samples. Although IL-based SPME is still at the beginning of its development stage, the results obtained by this work showed that it is a promising simple, fast and sensitive sample preparation method.     

Analysis of phenylurea and propanil herbicides by solid-phase microextraction and liquid chromatography combined with post-column photochemically induced fluorimetry derivatization and fluorescence detection

This study examines the application of solid-phase microextraction coupled with high performance liquid chromatography combined with post-column photochemically induced fluorimetry derivatization and fluorescence detection (SPME-HPLC-PIF-FD) for the determination of four phenylurea herbicides (monolinuron, diuron, linuron and neburon) and propanil in groundwater. Direct immersion (DI) SPME was applied using a 60 μm polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber for the extraction of the pesticides from groundwater samples. An AQUASIL C₁₈ column (150 mm × 4.6 mm i.d., 5 μm) was used for separation and determination in HPLC. The method was evaluated with respect to the limits of detection (LODs) and the limits of quantification (LOQs) according to IUPAC. The limits of detection varied between 0.019 μg L⁻¹ and 0.034 μg L⁻¹. Limits of quantification ranged between 0.051 μg L⁻¹ and 0.088 μg L⁻¹. These values meet the recommended limits for individual pesticides in groundwater (0.1 μg L⁻¹) established by the EU. Recoveries ranged between 86% and 105% and relative standard deviation values between 2% and 8%.     

Determination of octylphenol and nonylphenol in aqueous sample using simultaneous derivatization and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry

A simple and fast sample preparation method for the determination of nonylphenol (NP) and octylphenol (OP) in aqueous samples by simultaneous derivatization and dispersive liquid–liquid microextraction (DLLME) was investigated using gas chromatography–mass spectrometry (GC/MS). In this method, a combined dispersant/derivatization catalyst (methanol/pyridine mixture) was firstly added to an aqueous sample, following which a derivatization reagent/extraction solvent (methyl chloroformate/chloroform) was rapidly injected to combine in situ derivatization and extraction in a single step. After centrifuging, the sedimented phase containing the analytes was injected into the GC port by autosampler for analysis. Several parameters, such as extraction solvent, dispersant solvent, amount of derivatization reagent, derivatization and extraction time, pH, and ionic strength were optimized to obtain higher sensitivity for the detection of NP and OP. Under the optimized conditions, good linearity was observed in the range of 0.1–1000 μg L⁻¹ and 0.01–100 μg L⁻¹ with the limits of detection (LOD) of 0.03 μg L⁻¹ and 0.002 μg L⁻¹ for NP and OP, respectively. Water samples collected from the Pearl River were analyzed with the proposed method, the concentrations of NP and OP were found to be 2.40 ± 0.16 μg L⁻¹ and 0.037 ± 0.001 μg L⁻¹, respectively. The relative recoveries of the water samples spiked with different concentrations of NP and OP were in the range of 88.3–106.7%. Compared with SPME and SPE, the proposed method can be successfully applied to the rapid and convenient determination of NP and OP in aqueous samples.     

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.     

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%.     

The investigation of electrospun polymer nanofibers as a solid-phase extraction sorbent for the determination of trazodone in human plasma

A novel micro-extraction procedure was developed through the use of an electrospun polymer nanofiber as a solid-phase extraction (SPE) sorbent to directly extract trazodone from human plasma. The target compound was then monitored by a high performance liquid chromatography with ultraviolet detector (HPLC-UV) system. Parameters of influencing the extraction efficiency, such as fiber diameter, fiber packing amount, eluted solvent, pH and ionic strength were investigated. Under the optimized conditions, a linear response for trazodone over the range of 20-2000 ng mL⁻¹ was achieved with a γ² value of 0.9996. The precision of the method was examined with relative standard deviations of 5.7, 2.7, 2.2% corresponding to 50, 200, and 500 ng mL⁻¹, respectively, of trazodone spiked into 0.1 mL of plasma samples. The extraction recoveries of 58.3-75.2% and the relative recoveries of 94.6-105.5% were obtained. The limit of detection (LOD) was determined to be 8 ng mL⁻¹. A 15 min of HPLC gradient was successfully applied to determine trazodone from human plasma. Due to its simplicity, selectivity and sensitivity, the method may be applied to pharmacokinetic and pharmacodynamic studies of drugs.     

Determination of organophosphorus pesticides in ecological textiles by solid-phase microextraction with a siloxane-modified polyurethane acrylic resin fiber

A novel solid-phase microextraction (SPME) fiber coating was prepared with siloxane-modified polyurethane acrylic resin by photo-cured technology. The ratio of two monomers was investigated to obtain good microphase separation structure and better extraction performance. The self-made fiber was then applied to organophosphorus pesticides (OPPs) analysis and several factors, such as extraction/desorption time, extraction temperature, salinity, and pH, were studied. The optimized conditions were: 15 min extraction at 25 °C, 5% Na₂SO₄ content, pH 7.0 and 4 min desorption in GC inlet. The self-made fiber coating exhibited better extraction efficiency for OPPs, compared with three commercial fiber coatings. Under the optimized conditions, the detection limits of 11 OPPs were from 0.03 μg L⁻¹ to 0.5 μg L⁻¹. Good recoveries and repeatabilities were obtained when the method was used to determine OPPs in ecological textile.