Preparation of polypyrrole-coated magnetic particles for micro solid-phase extraction of phthalates in water by gas chromatography-mass spectrometry analysis

In this work, polypyrrole (PPy)-coated Fe(3)O(4) magnetic microsphere were successfully synthesized, and applied as a magnetic sorbent to extract and concentrate phthalates from water samples. The PPy-coated Fe(3)O(4) magnetic microspheres had the advantages of large surface area, convenient and fast separation ability. The PPy coating of magnetic microspheres contributed to preconcentration of phthalates from water sample, due to the π-π bonding between PPy coating and the analytes. Also, the coating could prevent aggregation of the microspheres, and improve their dispersibility. In this study, seven kinds of phthalates were selected as model analytes, including dimethyl phthalate (DMP), diethyl phthalate (DEP), di-iso-butyl phthalate (DIBP), di-n-butyl phthalate (DBP), benzylbutyl phthalate (BBP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DNOP), and gas chromatography-mass spectrometry (GC-MS) was introduced to detect the phthalates after sample pretreatment. Important parameters of the extraction procedure were investigated, and optimized including eluting solvent, the amount of Fe(3)O(4)@PPy particles, and extraction time. After optimization, the procedure took only 15 min to extract and concentrate analytes with high efficiency. Validation experiments showed that the optimized method had good linearity (0.985-0.998), precision (3.4-11.7%), high recovery (91.1-113.4%), and the limits of detection were from 0.006 to 0.068 μg/L. The results indicated that the novel method had advantages of convenience, good sensitivity, high efficiency, and it could also be applied successfully to analyze phthalates in real water sample.     

Preparation of Fe3O4@C@PANI magnetic microspheres for the extraction and analysis of phenolic compounds in water samples by gas chromatography-mass spectrometry

In this work, core-shell structure Fe(3)O(4)@C@polyaniline magnetic microspheres were synthesized using simple hydrothermal reactions. The carbon-coated magnetic microspheres (Fe(3)O(4)@C) were first synthesized by a hydrothermal reaction, and then aniline was polymerized on the magnetic core via another hydrothermal reaction. Then, the obtained Fe(3)O(4)@C@polyaniline magnetic microspheres were applied as magnetic adsorbents for the extraction of aromatic molecules due to π-π interactions between polyaniline shell and aromatic compounds. In our study, five kinds of phenols including phenol, 2,4-dichlorophenol (DCP), 2,4,5-trichlorophenol (TCP), pentachlorophenol (PCP) and bisphenol A (BPA) were selected as the model analytes to verify the extraction ability of Fe(3)O(4)@C@PANI microspheres. After derivatization, the phenols were detected using gas chromatography-mass spectrometry (GC-MS). The dominant parameters affecting enrichment efficiency were investigated and optimized. Under the optimal conditions, the proposed method was evaluated, and applied to the analysis of phenols in real water samples. The results demonstrated that our proposed method based on Fe(3)O(4)@C@polyaniline magnetic microspheres had good linearity (r(2)>0.991), and limits of quantification (2.52-29.7 ng/mL), high repeatability (RSD<13.1%) and good recovery (85.3-110.6%).     

Decyl‐perfluorinated magnetic mesoporous microspheres for extraction and analysis perfluorinated compounds in water using ultrahigh‐performance liquid chromatography–mass spectrometry

In this work, the interior‐walls decyl‐perfluorinated functionalized magnetic mesoporous microspheres (F₁₇–Fe₃O₄@mSiO₂) were synthesized for the first time, and applied as adsorbents to extract and concentrate perfluorinated compounds (PFCs) from water samples. The fluorous functionalized interior pore‐walls contributed to the high‐selective preconcentration of PFCs due to fluorous affinity; and abundant silanol groups on the exterior surface of microspheres contributed to the good dispersibility in water sample. Four kinds of PFCs were selected as model analytes, including perfluorooctanoic acid, perfluorononanoic acid, perfluorododecanoic acid, and perfluorooctane sulphonate. In addition, UHPLC‐ESI/MS/MS was introduced to the fast and sensitive detection of the analytes after sample pretreatment. Important parameters of the extraction procedure were optimized, including salinity, eluting solvent, the amount of F₁₇–Fe₃O₄@mSiO₂ microspheres, and extraction time. The optimized procedure took only 10 min to extract analytes with high recoveries and merely 800‐μL acetonitrile to elute analytes from the magnetic adsorbents. Validation experiments showed good linearity (0.994–0.998), precision (2.6–7.6%), high recovery (93.4–105.7%) of the proposed method, and the limits of detection were from 0.008 to 0.125 μg/L. The F₁₇–Fe₃O₄@mSiO₂ magnetic microspheres have the advantages of great dispersibility in aqueous solution, high specificity of extraction, large surface area, and efficient separation ability. The results showed that the proposed method based on F₁₇–Fe₃O₄@mSiO₂ microspheres is a simple, fast, and sensitive tool for the analysis of PFCs in water sample.     

Enrichment and determination of polybrominated diphenyl ethers in environmental water samples by magnetic solid‐phase extraction with core–shell magnetic carbon microspheres before gas chromatography with mass spectrometry

Core–shell magnetic carbon microspheres were synthesized by a simple hydrothermal method and used as a novel magnetic solid‐phase extraction adsorbent for the sensitive determination of polybrominated diphenyl ethers in environmental water samples. Gas chromatography with negative chemical ionization mass spectrometry was adopted for the detection. Box–Behnken design was used to investigate and optimize important magnetic solid‐phase extraction parameters through response surface methodology. Under the optimal conditions, low limits of detection (0.07–0.17 ng·L^?1), a wide linear range (1–1000 ng·L^?1), and good repeatability (0.80–4.58%) were achieved. The developed method was validated with several real water samples, and satisfactory results were obtained in the range of 72.8–97.9%. These results indicated that core–shell magnetic carbon microspheres have great potential as an adsorbent for the magnetic solid‐phase extraction of polybrominated diphenyl ethers at trace levels from environmental water samples.     

Dispersive solid-phase extraction based on oleic acid-coated magnetic nanoparticles followed by gas chromatography-mass spectrometry for UV-filter determination in water samples

A sensitive analytical method to concentrate and determine extensively used UV filters in cosmetic products at (ultra)trace levels in water samples is presented. The method is based on a sample treatment using dispersive solid-phase extraction (dSPE) with laboratory-made chemisorbed oleic acid-coated cobalt ferrite (CoFe(2)O(4)@oleic acid) magnetic nanoparticles (MNPs) as optimized sorbent for the target analytes. The variables involved in dSPE were studied and optimized in terms of sensitivity, and the optimum conditions were: mass of sorbent, 100mg; donor phase volume, 75 mL; pH, 3; and sodium chloride concentration, 30% (w/v). After dSPE, the MNPs were eluted twice with 1.5 mL of hexane, and then the eluates were evaporated to dryness and reconstituted with 50 μL of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) for the injection into the gas chromatography-mass spectrometry (GC-MS). Under the optimized experimental conditions the method provided good levels of repeatability with relative standard deviations below 16% (n=5, at 100 ng L(-1) level). Limit of detection values ranged between 0.2 and 6.0 ng L(-1), due to the high enrichment factors achieved (i.e., 453-748). Finally, the proposed method was applied to the analysis of water samples of different origin (tap, river and sea). Recovery values showed that the matrices under consideration do not significantly affect the extraction process.     

Magnetic solid-phase extraction based on octadecyl functionalization of monodisperse magnetic ferrite microspheres for the determination of polycyclic aromatic hydrocarbons in aqueous samples coupled with gas chromatography-mass spectrometry

Monodisperse magnetic C₁₈ microspheres were prepared based on the three-step reactions of solvothermal reduction, silanization and alkylation. The microspheres are of uniform sizes in the range of 200-260 nm. The structure of synthesized magnetic C₁₈ microspheres was studied by transmission electron microscopy, scanning electron microscopy, X-ray diffraction patterns, element analysis and vibrating sample magnetometry. This material has a high magnetic saturation value of 59 emu g⁻¹ and is easy to manipulate under a magnet. The prepared material was used for the preconcentration of the polycyclic aromatic hydrocarbon in water. The effects of desorption solvent and the amount of adsorbent on the preconcentration were also investigated. The results showed that the developed method was beneficial for the preconcentration of PAHs of middle molecular weight.     

亲水改性C18填料的制备及其在萃取水中酚类化合物中的应用

通过在甲基丙烯酸十八酯(SMA)中加入亲水性单体甲氧基聚乙二醇甲基丙烯酸酯(PEGMEA),以1-正丙醇/1,4-丁二醇为致孔剂,热聚合得到具有一定亲水性的新型C18填料,并将该填料应用于固相萃取(SPE)富集水中的酚类化合物。实验优化了致孔剂的配比、SPE过程中上样溶液pH值、洗脱剂种类等参数。在上样溶液pH为6.0,以5.0 mL乙腈为洗脱剂的优化条件下,5种酚类化合物在0.5～10 mg/L范围内呈良好的线性关系,检出限为0.16～0.47 mg/L。所制备的亲水改性C18材料已成功用于大辽河水样中酚的检测,平均加标回收率为64.33%～92.14%, 相对标准偏差为4.2%～6.4%(n=3),证明了该填料对环境水样中痕量酚类化合物富集的可靠性。     

Simple and rapid determination of phthalates using microextraction by packed sorbent and gas chromatography with mass spectrometry quantification in cold drink and cosmetic samples

A simple and rapid method using microextraction by packed sorbent coupled with gas chromatography and mass spectrometry has been developed for the analysis of five phthalates, namely, diethyl phthalate, benzyl‐n‐butyl phthalate, dicyclohexyl phthalate, di‐n‐butyl phthalate, and di‐n‐propyl phthalate, in cold drink and cosmetic samples. The various parameters that influence the microextraction by packed sorbent performance such as extraction cycle (extract–discard), type and amount of solvent, washing solvent, and pH have been studied. The optimal conditions of microextraction using C₁₈ as the packed sorbent were 15 extraction cycles with water as washing solvent and 3 × 10 μL of ethyl acetate as the eluting solvent. Chromatographic separation was also optimized for injection temperature, flow rate, ion source, interface temperature, column temperature gradient and mass spectrometry was evaluated using the scan and selected ion monitoring data acquisition mode. Satisfactory results were obtained in terms of linearity with R² >0.9992 within the established concentration range. The limit of detection was 0.003–0.015 ng/mL, and the limit of quantification was 0.009–0.049 ng/mL. The recoveries were in the range of 92.35–98.90% for cold drink, 88.23–169.20% for perfume, and 88.90–184.40% for cream. Analysis by microextraction by packed sorbent promises to be a rapid method for the determination of these phthalates in cold drink and cosmetic samples, reducing the amount of sample, solvent, time and cost.     

Preparation of phenyl‐functionalized magnetic mesoporous silica microspheres for the fast separation and selective enrichment of phenyl‐containing peptides

Peptide enrichment before mass spectrometry analysis is essential for large‐scale peptidomic studies, but challenges still remain. Herein, magnetic mesoporous silica microspheres with phenyl group modified interior pore walls were prepared by a facile sol–gel coating strategy, and were successfully applied for selective enrichment of phenyl‐containing peptides in complex biological samples. The newly prepared nanomaterials possessed abundant silanol groups in the exterior surface and numerous phenyl groups in the interior pore walls, as well as a large surface area (592.6 m²/g), large pore volume (0.33 cm³/g), uniform mesopores (3.8 nm), strong magnetic response (29.3 emu/g), and good dispersibility in aqueous solution. As a result of the unique structural properties and size‐exclusion effect, the core–shell phenyl‐functionalized magnetic mesoporous silica microspheres exhibited excellent performance in fast separation and selective enrichment of phenyl‐containing peptides, and the adsorption capacity for bradykinin reached 22.55 mg/g. In addition, selective enrichment of phenyl‐containing peptides from complex samples that are consist of peptides, large proteins, and human serum were achieved by using the as‐prepared microspheres, followed by high‐performance liquid chromatography with ultraviolet detection and electrospray ionization quadrupole time‐of‐flight mass spectrometry analysis. These results demonstrated the as‐prepared microspheres would be a potential candidate for endogenous phenyl‐containing peptides enrichment and biomarkers discovery in peptidome analysis.     

Aminosilanized magnetic carbon microspheres for the magnetic solid‐phase extraction of bisphenol A,bisphenol AF,and tetrabromobisphenol A from environmental water samples

Aminosilanized magnetic carbon microspheres as a novel adsorbent were designed and fabricated. The adsorbent was used for the magnetic solid‐phase extraction of bisphenols at trace levels from environmental water samples before liquid chromatography with tandem mass spectrometry analysis. The structure, surface, and magnetic behavior of the as‐prepared aminosilanized magnetic carbon microspheres were characterized by elemental analysis, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, powder X‐ray diffraction, and vibrating sample magnetometry. The effects of the experimental parameters were investigated by the Plackett–Burman design, and then the parameters that were significant to the extraction efficiencies were optimized through a response surface methodology. The aminosilanized magnetic carbon microspheres exhibited high adsorption efficiency and selectivity for bisphenols. Under optimal conditions, low limits of detection (0.011–2.22 ng/L), and a wide linear range (2–3 orders of magnitude), good repeatability (4.7–7.8%, n = 5), and reproducibility (6.0–8.3%, n = 3) were achieved. The results demonstrate that the novel adsorbent possesses great potentials in the determination of trace levels of bisphenols in environmental water samples.     

Fluorocarbon-bonded magnetic mesoporous microspheres for the analysis of perfluorinated compounds in human serum by high-performance liquid chromatography coupled to tandem mass spectrometry

We report herein an extraction method for the analysis of perfluorinated compounds in human serum based on magnetic core–mesoporous shell microspheres with decyl-perfluorinated interior pore-walls (Fe₃O₄@mSiO₂-F₁₇). Thanks to the unique properties of the Fe₃O₄@mSiO₂-F₁₇ microspheres, macromolecules like proteins could be easily excluded from the mesoporous channels due to size exclusion effect, and perfluorinated compounds (PFCs) in protein-rich biosamples such as serum could thus be directly extracted with the fluorocarbon modified on the channel wall without any other pretreatment procedure. The PFCs adsorbed Fe₃O₄@mSiO₂-F₁₇ microspheres could then be simply and rapidly isolated by using a magnet, followed by being identified and quantified by LC–MS/MS (high-performance liquid chromatography coupled to tandem mass spectrometry). Five perfluorinatedcarboxylic acids (C6, C8–C11) and perfluorooctane sulfonate (PFOS) were selected as model analytes. In order to achieve the best extraction efficiency, some important factors including the amount of Fe₃O₄@mSiO₂-F₁₇ microspheres added, adsorption time, type of elution solvent, eluting solvent volume and elution time were investigated. The ranges of the LOD were 0.02–0.05 ng mL⁻¹ for the six PFCs. The recovery of the optimized method varies from 83.13% to 92.42% for human serum samples.     

Preparation of magnetic surface molecularly imprinted polymers for the selective extraction of triazines in environmental water samples

ABSTRACT

In this work, a magnetic molecularly imprinted polymer (Fe₃O₄@SiO₂@MIPs) was prepared via a surface-imprinted method for the determination of the triazines in environmental water samples combined with high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). The Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer showed that the Fe₃O₄@SiO₂@MIPs was successfully synthesised and exhibited superparamagnetism. The isotherm adsorption, selectivity and adsorption kinetics experiments showed that the Fe₃O₄@SiO₂@MIPs exhibited excellent specific recognition and fast adsorption equilibrium for triazines. The adsorption process is spontaneous and endothermic. The isotherm adsorption was consistent with Scatchard model and adsorption kinetic fit pseudo-second-order kinetic model. Under the optimised adsorption conditions, the Fe₃O₄@SiO₂@MIPs was directly used to selectively enrich six triazines in environmental water samples. The enrichment volume was up to 500 mL, and the matrix effects were down to 0.7–12.4%. The built method has excellent linearities in the range of 0.25–500 ng L^?1 with R² in the range of 0.998–0.999, lower limit of detections (0.02–0.08 ng L^?1) and higher precision (2.4–7.2%). The Fe₃O₄@SiO₂@MIPs is expected to be widely applied to the direct enrichment of triazines in bulk environmental water samples.     

Novel thionin-functionalised core shell magnetic nanoparticles for dispersive solid-phase extraction of Hg(II) in food and water samples

To develop an accurate and precise method for separation and pre-concentration of Hg(II), a novel thionin functionalised core shell structure magnetic material has been prepared and characterised. The extraction ability of the material was evaluated by magnetic solid-phase extraction coupled with inductively coupled plasma mass spectrometry determination of Hg(II) in food and water samples. Combining the advantages of magnetic separation with selective extraction of thionin towards Hg(II), the material exhibits enhanced enrich selectivity and efficiency for Hg(II). The experimental parameters influencing Hg(II) extraction efficiency, including pH of the aqueous solution, the dosage of the adsorbent, extraction time and sample volume, were systematically investigated. Under the optimised conditions, concentration of Hg(II) at 1.0 μg L^?1 can be successfully enriched by the material without the interference of the common co-existing ions. The enrichment factor and adsorption capacity were 250 and 75.2 mg g^?1, and precise of the method was confirmed by analysing the spiked food, water samples and standard water reference samples with the recoveries of 92.5–101.8%.     

Development of a solid-phase extraction with capillary liquid chromatography tandem mass spectrometry for analysis of estrogens in environmental water samples

Capillary liquid chromatography (cLC) hyphenated with tandem mass spectrometry (MS-MS) was used to separate and quantitate trace concentrations of five estrogens in aqueous samples. New C(18)-based sorption materials bound to the silica support by monomeric and polymeric mechanisms were compared and tested for solid-phase extraction (SPE) of selected analytes with respect to optimization of their preconcentration yield. Application of an endcapped, monomer-bound preconcentration Discovery DSC-18Lt column under the optimized conditions provides yields in the range from 95 to 100% with a high repeatability (n=3, RSD≤7.2%). Using the electrospray ionization in the positive mode (ESI+), the cLC-MS-MS system (the Zorbax SB C18 capillary column and a binary mobile phase of acetonitrile and water containing 0.1% formic acid in both the components) was optimized to attain a sufficient retention of the early eluting estriol, a satisfactory resolution of the analytes and the maximum sensitivity of the determination. Both the isocratic and gradient elution were used and the optimized gradient method permitted analyses of aqueous environmental samples in 14 min within a linearity range from 6.1 to 25.0 (LOQ of analytes) to 500 ng/L and with a very good linearity (r>0.9981) for all the estrogens studied. The detection limits are in the range from 3.0 to 6.8 ng/L (1 μL injection volume). Six environmental water samples were analyzed and the studied estrogens were found in the Vltava river sample collected in Prague (13.2 ng/L for 17β-estradiol) and in the inlet to the wastewater treatment plant in Prague, at an overall concentration of 371.4 ng/L.     

Preparation and application of solid-phase microextraction fiber based on molecularly imprinted polymer for determination of anabolic steroids in complicated samples

A relatively selective, chemically and physically robust SPME fiber was developed in a simple way with testosterone-imprinted polymer, and then directly coupled with gas chromatography-mass spectrometry (GC-MS) for selective extraction and analysis of anabolic steroids. The factors influencing polymerization (i.e., cross-linker, polymerization solvent, polymerization time) were optimized in detail and the polymer was characterized by scanning electron microscope, infrared spectrometer and thermogravimetric analyzer. Furthermore, the extraction performance of the MIP-coated SPME fibers such as extraction ability and selectivity was evaluated. Moreover, the interaction mode between target analytes and fiber coating was deducted. Finally, the method for extraction and determination of androsterone, stanolone, androstenedione and methyltestosterone by the homemade MIP-coated SPME fibers with GC-MS was obtained. It was applied to the simultaneous analysis of four anabolic steroids in the spiked human urine with the satisfactory recoveries.     

Octyl‐modified magnetic graphene as a sorbent for the extraction and simultaneous determination of fragrance allergens,musks, and phthalates in aqueous samples by gas chromatography with mass spectrometry

An effective, simple, and low‐cost sample preparation method based on dispersive SPE followed by GC with MS is developed for the multianalyte determination of fragrance allergens, musks, and phthalates, at sub‐ppb levels. The extraction procedure is based on a novel magnetic graphene sorbent, which is functionalized with octylamine, taking advantage of the functionalization's hydrophobic properties and π–π interactions with the analytes. Two alkyl amines, the octylamine and octadecylamine are studied to introduce alkyl chains in the basal plane of graphene. Magnetic graphene‐ octadecylamine is proved to be highly hydrophobic to such a degree that is hard to disperse in the bulk aqueous matrixes. Because of this behavior, its extraction efficiency for the target analytes is low. The synthesis and applicability of the magnetic graphene‐octylamine as more favored sorbent are optimized in terms of the most determining experimental conditions. The detection and quantification limits, which are calculated based on S/N ratio of 3 and 10, respectively, ranged from 0.29 to 3.2 ng L^?1 and from 0.89 to 9.6, respectively. The dispersive SPE is successfully applied to routine analysis for the determination of the target analytes in samples from municipal treatment plant of Ioannina (Greece), from Pamvotis Lake and baby bathwater. The reproducibility of the spiked biological treatment plant water sample is evaluated and the relative standard deviation values range between 2.1 and 9.4%.     

Selective enrichment of glycopeptides for mass spectrometry analysis using C18 fractionation and titanium dioxide chromatography

Comprehensive glycoprotein characterization based on mass spectrometry (MS) is challenging because of low concentration of glycopeptides and suppression effect of abundant non-glycosylated peptides in MS. Therefore, it is vital to enrich glycopeptides before MS analysis. A new method was developed to selectively enrich glycopeptides from complex sample by coupling C18 fractionation with titanium dioxide (TiO(2)) enrichment. The new method allows to selectively enrich N-linked glycopeptides with various glycan forms and different sequence lengths. Compared with single TiO(2) method, the established method demonstrated higher glycopeptide selectivity and higher glycosylation heterogeneity coverage. Further application of this method to mixture of non-glycosylated protein and glycoprotein digests at different levels reveals the feasibility of enrichment of tryptic glycopeptides from simple proteomics samples.     

Development of a stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry method for determining synthetic musks in water samples

This study presents the development of an analytical method for determining 9 synthetic musks in water matrices. The developed method is based on stir bar sorptive extraction (SBSE), coated with polydimethylsiloxane, and coupled with a thermal desorption–gas chromatography–mass spectrometry system (TD–GC–MS). SBSE can efficiently trap and desorb the analytes providing low limits of detection (between 0.02 ng L⁻¹ and 0.3 ng L⁻¹). Method validation showed good linearity, repeatability and reproducibility for all compounds. Furthermore, the limited manipulation of the sample required in this method implies a significant decrease of the risk of external contamination of the samples. The performance of the method in real samples was evaluated by analysing biological wastewater treatment plant (WWTP) influent and effluent samples, reverse osmosis treatment plant effluents and river waters. The most abundant musk was galaxolide with values up to 2069 ng L⁻¹ and 1432 ng L⁻¹ in the influent and effluent of urban WWTP samples, respectively. Cashmeran, Pantolide and Tonalide were also detected in all the matrices with values up to 94 ng L⁻¹, 26 ng L⁻¹ and 88 ng L⁻¹, respectively. Although in Europe the use of nitromusks in cosmetics is prohibited, musk xylene and musk ketone were detected both in the WWTP and in the river samples. As far as we know, this is the first time than a SBSE method coupled with TD is applied for the determination of synthetic musks in water samples.     

A fully automated system with on-line micro solid-phase extraction combined with capillary liquid chromatography-tandem mass spectrometry for high throughput analysis of microcystins and nodularin-R in tap water and lake water

Microcystins and nodularins are cyclic peptide hepatotoxins and tumour promoters from cyanobacteria. The present study describes the development, validation and practical application of a fully automated analytical method based on on-line micro solid-phase extraction-capillary liquid chromatography-tandem mass spectrometry for the simultaneous determination of seven microcystins and nodularin-R in tap water and lake water. Aliquots of just 100 μL of water samples are sufficient for the detection and quantification of all eight toxins. Selected reaction monitoring was used to obtain the highest sensitivity. Good linear calibrations were obtained for microcystins (50-2000ng/L) and nodularin-R (25-1000 ng/L) in spiked tap water and lake water samples. Excellent interday and intraday repeatability were achieved for eight toxins with relative standard deviation less than 15.7% in three different concentrations. Acceptable recoveries were achieved in the three concentrations with both tap water matrix and lake water matrix and no significant matrix effect was found in tap water and lake water except for microcystin-RR. The limits of detection (signal to noise ratio=3) of toxins were lower than 56.6 ng/L which is far below the 1 μg/L defined by the World Health Organization provisional guideline for microcystin-LR. Finally, this method was successfully applied to lake water samples from Tai lake and proved to be useful for water quality monitoring.     

Preparation of C18 composite solid-phase microextraction fiber and its application to the determination of organochlorine pesticides in water samples

In this work, a C18 composite solid-phase microextraction (SPME) fiber was prepared with a new method and applied to the analysis of organochlorine pesticides (OCPs) in water sample. A stainless steel wire (o.d. 127 μm) was used as the substrate, and a mixture of the C18 particle (3.5 μm) and the 184 silicone was used as the coating material. During the process of fiber preparation, a section of capillary column was used to fix the mixture onto the stainless steel wire and to ensure the constant of coating thickness. The prepared fiber showed excellent thermal stability and solvent resistance. By coupling with gas chromatography–mass spectrometry (GC–MS), the fiber exhibited wide linearity (2–500 ng L⁻¹) and good sensitivity for the determination of six OCPs in water samples, the OCPs tested included hexachlorobezene, trans-chlordane, cis-chlordane, o,p-DDT, p,p-DDT and mirex. Not only the extraction performance of the newly prepared fiber was more than seven times higher than those of commercial fibers, the limits of detections (LODs) (0.059–0.151 ng L⁻¹) for OCPs achieved under optimized conditions were also lower than those of reported SPME methods. The fiber was successfully applied to the determination of OCPs in real water samples by using developed SPME–GC–MS method.