Coated Stir Bar Research Articles

Membrane protected C18 coated stir bar sorptive extraction combined with high performance liquid chromatography-ultraviolet detection for the determination of non-steroidal anti-inflammatory drugs in water samples

By wrapping a porous membrane around the coated stir bar, a novel membrane protected stir bar sorptive extraction (MPSBSE) was proposed to filter out the high molecular weight interferences (such as humic acid), resulting in the analysis of real environmental water samples without filtration or centrifugation. Hydrophilic and hydrophobic membranes were compared and hydrophobic polytetrafluoroethylene (PTFE) membrane impregnated with methanol was employed to protect the C18 coated stir bar. The impregnated methanol improves the transfer of target analytes from sample solution to the pores and lumen of the membrane, and then to the coated stir bar inside. By combining C18-MPSBSE with HPLC-UV, a method was proposed for the direct determination of two common non-steroidal anti-inflammatory drugs, Ketoprofen (KEP) and Naproxen (NAP) in complex water samples. Under the optimized conditions, the limit of detections of KEP and NAP are 7.89, 9.52μgL−1 in the waste water and 7.69, 6.90μgL−1 in the pure water, respectively, with the enrichment factors of 32.0–49.1-fold. Besides, the lifetime of the prepared C18 stir bar protected by PTFE membrane (50 times) is longer than that of C18 stir bar without membrane protection (20 times), indicating that the friction damage of SBSE coating during extraction was effectively avoided. The developed method was successfully applied to the analysis of KEP and NAP in domestic sewage and campus lake water samples.

ICE Concentration Linked with Extractive Stirrer (ICECLES)

Trace and ultra-trace analysis can be difficult to achieve, especially for polar, more volatile, and/or thermally unstable analytes. A novel technique, coined ICE Concentration Linked with Extractive Stirrer (ICECLES), may help address this problem. The implementation of ICECLES described here combines stir bar sorptive extraction (SBSE) with freeze concentration (FC), where an aqueous solution is frozen during SBSE in order to concentrate analytes into a polydimethylsiloxane (PDMS) coated stir bar. Five test probe molecules with a range of log Kows (2-butanol, benzyl alcohol, benzaldehyde, dimethyl trisulfide and bromobenzene) were prepared from aqueous solutions using ICECLES. Thermal desorption gas–chromatography mass–spectrometry was then used to quantify these analytes. Parameters affecting the performance of ICECLES (e.g., freeze rate) were evaluated, with extraction at lower speeds resulting in higher extraction efficiencies, whereas the freeze rate and initial analyte concentration only had a minor effect. ICECLES produced much higher extraction efficiencies than SBSE alone, with signal enhancements of up to 474× SBSE. ICECLES also provided excellent reproducibility and lower LODs than SBSE for all compounds tested. ICECLES performed well when used to analyze multiple triazine pesticides and breakdown products in environmental surface waters. Overall, the ICECLES technique was excellent at preparing aqueous samples for trace analysis and shows promise as a novel analytical sample preparation technology.

Development of Carbon Nanotube-Polyamide Nanocomposite-based Stir Bar Sorptive Extraction Coupled to HPLC-UV Applying Response Surface Methodology for the Analysis of Bisphenol A in Aqueous Samples.

A novel nanocomposite based on reinforcing of multiwalled carbon nanotubes in polyamide (PA) was prepared by solvent exchange method as stir bar coating. The morphology and surface characteristic of PA and CNT/PA coated stir bars were investigated using scanning electron microscopy. The stir bar coated by CNT/PA nanocomposite was used as an extraction device for stir bar sorptive extraction of bisphenol A from aqueous samples followed by high performance liquid chromatography-UV detection. The effect of CNTs doping level and oxidation of CNTs on the extraction capability of the coating was investigated. Response surface methodology applying central composite design was used for modeling and optimization of important factors influencing the extraction and desorption processes including extraction time, salt and methanol content, desorption solvent, its volume and desorption time. Limit of detection and linear dynamic range of the method were 0.3 ng mL-1 and 1-10 ng mL-1, respectively. The method precision (RSD%) with four replicate determinations was 4.9% for distilled water at the concentration level of 10 ng mL-1 The obtained RSD% for reproducibility of stir bars was 7.4%. The developed method was successfully applied to the bottled mineral water samples, while the relative recoveries (RR%) were obtained to be in the range of 92.0-101.9%.

Coupling of multi-walled carbon nanotubes/polydimethylsiloxane coated stir bar sorptive extraction with pulse glow discharge-ion mobility spectrometry for analysis of triazine herbicides in water and soil samples

An analytical method based on stir bar sorptive extraction (SBSE) coupled with pulse glow discharge-ion mobility spectrometry (PGD-IMS) was developed for analysis of three triazine pesticide residues in water and soil samples. An injection port with sealing device and stir bars hold device were designed and constructed to directly position the SBSE fiber including the extracted samples into the heating device, making desorption and detection of analytes proceeded simultaneously. The extraction conditions such as SBSE solid phase material, extraction time, extraction temperature, pH value and salt concentration were optimized. Mixture of MWCNTs-COOH and PDMS were shown to be effective in enriching the triazines. The LODs and LOQs of three triazines were found to be 0.006–0.015μgkg−1 and 0.02–0.05μgkg−1, and the linear range was 0.05–10μgL−1 with determination coefficients from 0.9987 to 0.9993. The SBSE-PGD-IMS method was environmentally friendly without organic solvent consumption in the entire experimental procedures, and it was demonstrated to be a commendable rapid analysis technique for analysis of triazine pesticide residues in environmental samples on site. The proposed method was applied for the analysis of real ground water, surface water and soil samples.

Preparation and Application of Polyimide Coated Stir Bar for Extraction of Phenols in Environmental Water Samples

Abstract A polyimide coated stir bar for sorptive extraction (SBSE) was prepared by immersion precipitation method and evaluated by using 5 phenols and chlorinated phenols as model samples. The highest extraction efficiency was achieved among all commercial extraction phases of SBSE reported. Experimental parameters including stirring speed, ionic strength, extraction temperature, extraction time, desorption temperature and time were optimized. Under the optimal conditions such as 100 mL of sample, 30% NaCl, extraction time of 30 min, stirring speed of 800 rpm and extraction temperature of 25 °C, the target compounds were recovered by thermal desorption at 300 °C for 4 min. More than two orders of magnitude of linearity were obtained (R ≥ 0.9995). LOQs (S/N = 10) were 0.028–0.123 μg L−1, and RSDs were in the range of 1.6%–9.7%. The polyimide SBSE coupled with gas chromatography-mass spectrometry was applied to the extraction and analysis of phenols in real samples, including tap water, sea water, and waste water. It was found that the polyimide SBSE showed high selectivity towards polar compounds and high thermostability up to 350 °C.

Polydimethylsiloxane/metal-organic frameworks coated stir bar sorptive extraction coupled to gas chromatography-flame photometric detection for the determination of organophosphorus pesticides in environmental water samples

In this work, the metal-organic frameworks (MOFs), MIL-101-Cr-NH2 was synthesized via a direct hydrothermal method, and a polydimethylsiloxane (PDMS)/MIL-101-Cr-NH2 coated stir bar was prepared by sol-gel technique. Good reproducibility was obtained for the preparation of PDMS/MIL-101-Cr-NH2 coated stir bar with the relative standard deviations (RSDs) ranging from 3.7 to 5.2% (n=7) in one batch, and from 5.4 to 9.2% (n=7) among different batches. With the high surface area and rich benzene ring structure of MIL-101-Cr-NH2, the prepared PDMS/MIL-101-Cr-NH2 coated stir bar presented higher extraction efficiency for target organophosphorus pesticides (OPPs, including phorate, diazinon, malathion, fenthion, quinalphos and ethion) over PDMS coated stir bar. Based on it, a new method of PDMS/MIL-101-Cr-NH2 coated stir bar sorptive extraction (SBSE) coupled to gas chromatography-flame photometric detection (GC-FPD) was proposed for the determination of six OPPs in environmental water samples. The operation parameters affecting the extraction efficiency of SBSE, including extraction time, stirring rate, desorption time and ionic strength, were investigated. Under the optimal conditions, the limits of detection (S/N=3) were found to be in the range of 0.043–0.085μgL−1 for the six target OPPs, and the linear range was 0.5–100μgL−1 for malathion and 0.2–100μgL−1 for other five OPPs. The RSDs of the proposed method evaluated at 1µgL−1 for each OPP were in the range of 5.9–8.7% (intra-day, n=7) and 6.1–10.7% (inter-day, n=5), respectively. The enrichment factors were varied from 110 to 151-fold (theoretical enrichment factor was 200-fold). The proposed method was applied to the analysis of OPPs in East Lake and pond water samples with recoveries in the range of 89.3–115% and 80.0–113% for the spiked East Lake and pond water samples, respectively.

Water-compatible graphene oxide/molecularly imprinted polymer coated stir bar sorptive extraction of propranolol from urine samples followed by high performance liquid chromatography-ultraviolet detection

Due to the high selectivity and stability, molecularly imprinted polymers (MIPs) have been successfully applied in stir bar sorptive extraction (SBSE) as a special coating to improve the selective extraction capability for target analytes. However, traditional MIPs usually suffer from incompatibility in aqueous media and low adsorption capacity, which limit the application of MIP coated stir bar in aqueous samples. To solve these problems, a water-compatible graphene oxides (GO)/MIP composite coated stir bar was prepared in this work by in situ polymerization. The prepared water-compatible GO/MIP coated stir bar presented good mechanical strength and chemical stability, and its recognition ability in aqueous samples was improved due to the polymerization of MIP in water environment, the adsorption capacity for target analytes was also increased by the addition of GO in MIP pre-polymer solution. Based on it, a method of water-compatible GO/MIP coated stir bar sorptive extraction combined with high performance liquid chromatography-ultraviolet detector (HPLV-UV) was proposed for the analysis of propranolol (PRO) in aqueous solution. The influencing factors of SBSE, such as sample pH, salt effect, stirring rate, extraction time, desorption solvent and desorption time, were optimized, and the analytical performance of the developed SBSE-HPLC-UV method was evaluated under the optimized conditions. The limit of detection (LOD) of the proposed method for PRO was about 0.37μgL−1, and the enrichment factor (EF) was 59.7-fold (theoretical EF was 100-fold). The reproducibility was also investigated at concentrations of 5μgL−1 and the relative standard deviation (RSD) was found to be 7.3% (n=7). The proposed method of GO/MIP coating-SBSE-HPLC-UV was successfully applied for the assay of the interested PRO drug in urine samples, and further extended to the investigation of the excretion of the drugs by monitoring the variation of the concentration of PRO in urine within 10h after drug-taking.

Polydimethylsiloxane/covalent triazine frameworks coated stir bar sorptive extraction coupled with high performance liquid chromatography-ultraviolet detection for the determination of phenols in environmental water samples

In this work, covalent triazine frameworks (CTFs) were introduced in stir bar sorptive extraction (SBSE) and a novel polydimethylsiloxane(PDMS)/CTFs stir bar coating was prepared by sol–gel technique for the sorptive extraction of eight phenols (including phenol, 2-chlorophenol, 2-nitrophenol, 4-nitrophenol, 2,4-dimethylphenol, p-chloro-m-cresol and 2,4-dichlorophenol, 2,4,6-trichlorophenol) from environmental water samples followed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection. The prepared PDMS/CTFs coated stir bar showed good preparation reproducibility with the relative standard deviations (RSDs) ranging from 3.5 to 5.7% (n=7) in one batch, and from 3.7 to 9.3% (n=7) among different batches. Several parameters affecting SBSE of eight target phenols including extraction time, stirring rate, sample pH, ionic strength, desorption solvent and desorption time were investigated. Under the optimal experimental conditions, the limits of detection (LODs, S/N=3) were found to be in the range of 0.08–0.30μg/L. The linear range was 0.25–500μg/L for 2-nitrophenol, 0.5–500μg/L for phenol, 2-chlorophenol, 4-nitrophenol as well as 2,4-dimethylphenol, and 1–500μg/L for p-chloro-m-cresol, 2,4-dichlorophenol as well as 2,4,6-trichlorophenol, respectively. The intra-day relative standard deviations (RSDs) were in the range of 4.3–9.4% (n=7, c=2μg/L) and the enrichment factors ranged from 64.9 to 145.6 fold (theoretical enrichment factor was 200-fold). Compared with commercial PDMS coated stir bar (Gerstel) and PEG coated stir bar (Gerstel), the prepared PDMS/CTFs stir bar showed better extraction efficiency for target phenol compounds. The proposed method was successfully applied to the analysis of phenols in environmental water samples and good relative recoveries were obtained with the spiking level at 2, 10, 50μg/L, respectively.

Polyaniline/cyclodextrin composite coated stir bar sorptive extraction combined with high performance liquid chromatography-ultraviolet detection for the analysis of trace polychlorinated biphenyls in environmental waters

A novel polyaniline/α-cyclodextrin (PANI/α-CD) composite coated stir bar was prepared by sol–gel process for the analysis of polychlorinated biphenyls (PCBs) in this work. The preparation reproducibility of the PANI/α-CD-coated stir bar was good, with relative standard deviations (RSDs) ranging from 2.3% to 3.7% (n=7) and 2.0% to 3.8% (n=7) for bar to bar and batch to batch, respectively. Based on it, a novel method of PANI/α-CD-coated stir bar sorptive extraction (SBSE) followed by high performance liquid chromatography-ultraviolet (HPLC-UV) detection was developed for the determination of trace PCBs in environmental waters. To obtain the best extraction performance for target PCBs, several parameters affecting SBSE, such as extraction time, stirring rate, and ionic strength were investigated. Under optimal experimental conditions, the limits of detection (LODs) of the proposed method for seven PCBs were in the range of 0.048–0.22μg/L, and the RSDs were 5.3–9.8% (n=7, c=1μg/L). Enrichment factors (EFs) ranging from 39.8 to 68.4-fold (theoretical EF, 83.3-fold) for target analytes were achieved. The proposed method was successfully applied for the determination of seven target PCBs in Yangtze River water and East Lake water, and the recoveries were in the range of 73.0–120% for the spiked East Lake water samples and 82.7–121% for the spiked Yangtze River water samples, respectively.

Molecularly imprinted stir bar sorptive extraction coupled with high-performance liquid chromatography for trace analysis of naphthalene sulfonates in seawater

In this paper, a novel molecularly imprinted polymer coated stir bar has been used to selectively extract naphthalene sulfonates (NSs) directly from seawater sample. 1-Naphthalene sulfonic acid (1-NS) was used as template molecule. The effects of different parameters were optimized on the extraction efficiency and the optimum conditions were established as: the absorption and desorption times were fixed, respectively, at 10 and 15 min, stirring speed was 700 rpm, pH was adjusted to 4.1, amount of NaCl was 1 mol L−1 and extraction process was performed at a temperature of 50 °C. The linear ranges were 2–250 µg L−1 for 3,6-NDS-1-OH (1-naphthol-3,6-disulfonic acid), 4–250 µg L−1 for 2-NS (2-naphthalene sulfonate) and 3–250 µg L−1 for 1-NS. The detection limits were within the range of 0.32–0.95 µg L−1. Under optimum conditions, the detection limits of the NSs were 0.84, 0.95 and 0.32 µg L−1 with the enrichment factor of 117-, 41- and 77-fold for 2-NS, 1-NS, and 6-NDS-1-OH, respectively. The repeatability of the method was satisfactory (0.53 ≤ RSD ≤6.0 %, n = 10). The method has been successfully applied for the analysis of trace amounts of three naphthalene sulfonates in seawater of Chabahar Bay.

Graphene oxide/polyethyleneglycol composite coated stir bar for sorptive extraction of fluoroquinolones from chicken muscle and liver

Graphene oxide (GO) is an ideal adsorbent for polar and less polar compounds due to its hexagonal carbon network structure with oxygen-containing groups, while its strong hydrophilicity and water solubility limited its application in sample pretreatment techniques. Herein, GO was composited with polyethyleneglycol (PEG) or polyaniline (PAN) through intermolecular interactions to improve its stability, and the GO/PEG and GO/PAN composite coated stir bars were prepared by sol–gel technique. Compared with GO/PAN composite and polydimethylsiloxane (PDMS) coated stir bar, the prepared GO/PEG composite coated stir bar exhibited higher extraction efficiency for five fluoroquinolones (FQs). Based on it, a method of GO/PEG composite coated stir bar sorptive extraction (SBSE) combined with high-performance liquid chromatography-fluorescence detector (HPLC-FLD) was proposed. The factors influencing SBSE, such as sample pH, salt effect, stirring rate, extraction time, desorption solvent and desorption time, were optimized, and the analytical performance of the developed SBSE-HPLC-FLD method was evaluated. The limits of detection (LODs) for five FQs were in the range of 0.0045–0.0079μgL−1, and the enrichment factors (EFs) were in the range of 41.5–65.5-fold (theoretical enrichment factor was 100-fold). The reproducibility was also investigated at concentrations of 0.05μgL−1 and the relative standard deviations (RSDs, n=6) were found to be in the range of 4.6–12.1%. The proposed method was successfully applied for the determination of FQs in chicken muscle and chicken liver samples.

MIL-101/GO Coated Stir Bar for SBSE to Determine Azo Dyes in Water Samples by UV–Vis Spectrophotometric Method

A composite of chromium (III) terephthalate metal-organic framework and graphene oxide (MIL-101/GO) coated stir bar was prepared by sol–gel technique for the first time and was employed for stir bar sorptive extraction (SBSE) of trace azo dyes amaranth, sunset yellow and carmine from water samples followed by UV–Vis spectrophotometric detection. A MIL-101/GO coating was first created on the glass bar surface. MIL-101/GO and MIL-101/GO coated stir bars were characterized. The enrichment factors of azo dyes by SBSE have been investigated in detail, and the optimized experimental parameters were obtained. Under the optimal conditions, a method for determination of trace amount of azo dyes was setup, and the detection limits of amaranth, sunset yellow and carmine were 2.3 ng/mL, 1.7 ng/mL and 1.6 ng/mL. The proposed method was successfully applied for the analysis of the three azo dyes in water samples.

Magnetic metal-organic frameworks coated stir bar sorptive extraction coupled with GC–MS for determination of polychlorinated biphenyls in fish samples

In this work, several kinds of the metal-organic framework (MOF) were evaluated the adsorption performance to PCB. Finally, MOF-5(Fe) was introduced in stir bar sorptive extraction (SBSE) as the adsorbent to extract six polychlorinated biphenyls (PCBs). Nd–Fe–B permanent magnet was employed as stir bar, which was then coated with Fe3O4-MOF-5(Fe) composite magnetic material, which was prepared by solvothermal method. The stir bar was then employed to extract and enrich six indicator PCBs (2,2′,5,5′-tetrachlorobiphenyl, 2,2′,4,5,5′-pentachlorobiphenyl, 2,2′,3,4,4′,5-hexachlorobiphenyl, 2,3,4,4,5-pentachlorobiphenyl, 2,2′,4,4′,5,5′-hexachlorobiphenyl, 2,2′,3,4,4′,5,5′-heptachlorobiphenyl) under stirring, then eluted by n-hexane under ultrasound. Its saturated adsorption amount was found to be 17.0–17.8mgg−1 and only 30min were needed to reach adsorption equilibrium. The MOF-stir bar can be reused for 60 times with the recovery above 80%, which exhibited good stability. Under the optimal experimental conditions, MOF-5(Fe) based SBSE was coupled with GC–MS for detecting six PCBs. The limits of detection (S/N=3) of the developed method were 0.061–0.096ngg−1, with enrichment factors of 50–100 fold. And the linear ranges were 0.01–500μgL−1. The new method was successfully applied to assess PCBs in fish samples with satisfactory recovery ranging from 94.3% to 97.5%.

Estimates of Octanol-Water Partitioning for Thousands of Dissolved Organic Species in Oil Sands Process-Affected Water.

In this study, the octanol-water distribution ratios (DOW, that is, apparent KOW at pH 8.4) of 2114 organic species in oil sands process-affected water were estimated by partitioning to polydimethylsiloxane (PDMS) coated stir bars and analysis by ultrahigh resolution orbitrap mass spectrometry in electrospray positive ((+)) and negative ((-)) ionization modes. At equilibrium, the majority of species in OSPW showed negligible partitioning to PDMS (i.e., DOW <1), however estimated DOW's for some species ranged up to 100,000. Most organic acids detected in ESI- had negligible partitioning, although some naphthenic acids (O2(-) species) had estimated DOW ranging up to 100. Polar neutral and basic compounds detected in ESI+ generally partitioned to PDMS to a greater extent than organic acids. Among these species, DOW was greatest among 3 groups: up to 1000 for mono-oxygenated species (O(+) species), up to 127,000 for NO(+) species, and up to 203,000 for SO(+) species. A positive relationship was observed between DOW and carbon number, and a negative relationship was observed with the number of double bonds (or rings). The results highlight that nonacidic compounds in OSPW are generally more hydrophobic than naphthenic acids and that some may be highly bioaccumulative and contribute to toxicity.

Determination of Carvedilol Enantiomers in Pharmaceutical Dosages by SBSE-HPLC Based on Diastereomer Formation.

A sensitive, selective and simple method for the simultaneous determination of carvedilol enantiomers in aqueous solution has been developed using stir bar sorptive extraction (SBSE) followed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. This method is based on the reaction of carvedilol enantiomers with (-)-menthyl chloroformate (MCF) after extraction by the SBSE method to produce diastereomeric derivatives. The separation was achieved by use of a C18 analytical column and the influence of mobile phase composition on the enantioseparation of carvedilol was studied. The applicability of two sorptive phases, poly(methyl methacrylate/ethyleneglycol dimethacrylate) (PA-EG) and polydimethylsiloxane, were tested for extraction of carvedilol enantiomers from aqueous samples. The obtained results showed excellent linear dynamic ranges and precisions for each of them. The least limit of detection for (S)- and (R)-carvedilol obtained 8 and 11 µg L(-1), respectively, using the PA-EG sorptive phase. Inter- and intra-mean recoveries were also satisfactory, ranging from 98 to 103%, with coefficient of variation in the range of 1-5% at three fortified levels using a PA-EG coated stir bar. The proposed SBSE (PA-EG)-MCF derivatization-HPLC-UV method was successfully applied to enantioselective analysis of carvedilol in water and pharmaceutical dosages, confirming the application of this method.

C18-coated stir bar sorptive extraction combined with HPLC-ICP-MS for the speciation of butyltins in environmental samples

A simple, rapid and sensitive method of C18-SBSE-HPLC-ICP-MS for the speciation of butyltins in environmental waters and sediments.

Cyromazine imprinted polymers for selective stir bar sorptive extraction of melamine in animal feed and milk samples.

In this work, a molecularly imprinted polymer (MIP) coated stir bar was prepared using a self-designed polytetrafluoroethylene (PTFE) mold and in situ polymerization, with cyromazine as the dummy template for the target melamine. The prepared MIP coated stir bar presented a uniform and porous surface as well as good chemical stability and selectivity for melamine. Based on it, a method of MIP coated stir bar sorptive extraction (SBSE) combined with high performance liquid chromatography-ultraviolet detection (HPLC-UV) was developed for the quantification of melamine in food samples. Significant factors affecting the extraction efficiency of melamine by MIP-SBSE, such as the extraction solvent and time, stirring rate, desorption solvent and time, were investigated thoroughly. Under the optimal conditions, the analytical performance of this method was evaluated. The detection limit of the developed method was 0.54 μg L(-1) for melamine with an enrichment factor of 42-fold and the relative standard deviation (RSD) of 6.1% (c = 5 μg L(-1), n = 7), and the linear range was 2-200 μg L(-1). The established method was applied for the determination of melamine in a variety of real samples including cat food, dog food, chicken feed A, chicken feed B and milk powder, and the recoveries for melamine in the spiked samples were in the range of 76.2-98.2%, 80.0-85.5%, 89.5-113%, 85.0-95.5% and 65.0-111%, respectively. The proposed method presented a good specific recognition ability and matrix interference resistance, and was demonstrated to be effective and sensitive for the analysis of melamine in animal food and milk samples.

Development of dual-templates molecularly imprinted stir bar sorptive extraction and its application for the analysis of environmental estrogens in water and plastic samples

In this study, a novel dual-template molecularly imprinted polymer (MIP)-coated stir bar was prepared and coupled with high-performance liquid chromatography (HPLC) for the analysis of environmental estrogens in complex samples. Dual-template MIP coating was homogeneous and porous with an average thickness of 5μm. Moreover, it could be used for at least 50 times and be kept for at least 12 months in a dryer without any damage. The MIP-coated stir bar showed excellent selectivity to bisphenols and steroids. The method for the determination of bisphenols and steroids in complex samples via MIP-coated stir bar sorptive extraction coupled with HPLC was developed. The method was successfully applied in the analysis of five estrogens in lake and river water samples with recoveries of 71.2– 96.4% and 62.8–98.0%, respectively. The method was also successfully applied to the analysis of five estrogens in three plastic samples with recoveries of 67.7–99.1%, 68.8–99.9%, and 74.8–101.8%. The limit of quantitation was 1.0–5.0μg/L. The proposed method is suitable for the simultaneous determination of multiple trace environmental estrogens in water and plastic samples.

Sorptive extraction using polydimethylsiloxane/metal–organic framework coated stir bars coupled with high performance liquid chromatography-fluorescence detection for the determination of polycyclic aromatic hydrocarbons in environmental water samples

In this work, metal–organic frameworks (MOFs, Al-MIL-53-NH2) were synthesized via the hydrothermal method, and novel polydimethylsiloxane/metal–organic framework (PDMS/MOFs, PDMS/Al-MIL-53-NH2)-coated stir bars were prepared by the sol–gel technique. The preparation reproducibility of the PDMS/MOFs-coated stir bar was good, with relative standard deviations (RSDs) ranging from 4.8% to 14.9% (n=7) within one batch and from 6.2% to 16.9% (n=6) among different batches. Based on this fact, a new method of PDMS/MOFs-coated stir bar sorptive extraction (SBSE) and ultrasonic-assisted liquid desorption (UALD) coupled with high performance liquid chromatography-fluorescence detection (HPLC-FLD) was developed for the determination of polycyclic aromatic hydrocarbons (PAHs) in environmental water samples. To obtain the best extraction performance for PAHs, several parameters affecting SBSE, such as extraction time, stirring rate, and extraction temperature, were investigated. Under optimal experimental conditions, wide linear ranges and good RSDs (n=7) were obtained. With enrichment factors (EFs) of 16.1- to 88.9-fold (theoretical EF, 142-fold), the limits of detection (LODs, S/N=3) of the developed method for the target PAHs were found to be in the range of 0.05–2.94ng/L. The developed method was successfully applied to the analysis of PAHs in Yangtze River and East Lake water samples.

Preparation of a stir bar coated with molecularly imprinted polymer and its application in analysis of dopamine in urine

A molecularly imprinted polymer coated stir bar (MIP-SB) using dopamine as a template was fabricated. The adsorptive capacity of the MIP-SB was almost 4 times over that of non-imprinted stir bar. The MIP-SB showed good extracting selectivity for dopamine when used to adsorb dopamine and its analogs. An analytical method to determine dopamine in urine sample was established by combining MIP-SB sorptive extraction with HPLC-fluorescence detector. The linear range of dopamine concentration was 0.378–18.9ng/ml with correlation coefficient of 0.9990, and the limit of quantification was about 0.0945ng/ml (S/N=10). The recoveries of dopamine with spiked urine samples at three different levels were between 92.3 and 106.9%, and the relative standard deviations were within 13.2% (n=3). The method is simple and suitable for the determination of dopamine in human urine for clinical application.