Imprinted Stir Bar Sorptive Extraction Research Articles

Anisotropic emulsion constructed boronate affinity imprinted Janus nanosheets for stir bar sorptive extraction of cis-diol-containing catechol

Molecularly imprinted stir bar sorptive extraction (MI-SBSE) is a powerful method for synchronously achieving rapid mixing and selective enrichment. Herein, boronate affinity imprinted Janus nanosheets for stir bar sorptive extraction of cis-diol-containing catechol is reported. In this work, Janus nanosheets (NS-2) with amino groups on one side and vinyl groups on the other side are firstly prepared by self-organized interfacial sol-gel process from O/W anisotropic emulsion templates. Then, boronate affinity imprinted polymer layer is grafted onto the vinyl groups of NS-2 by initiating a precipitation polymerization (NS-2-MIPs). Finally, NS-2-MIPs are attached to the aldehyde functionalizedglass tube with the magnetic inner core. Finally, MI-SBSE was used for selective enrichment of catechol, which is a typical endocrine disrupting chemical. The effects of solution pH, adsorption kinetics, isotherms, selectivity as well as the regeneration on the catechol adsorption onto the NS-2-MIPs are investigated in detail. NS-2-MIPs show largely enhanced adsorption capacity and good selectivity toward catechol than non-imprinted nanosheets (NS-2-NIPs). The maximum adsorption capacities achieve 286.3 μmol g−1 at 308 K and 263.0 μmol g−1 at 298 K, and the quick adsorption equilibrium reach within 30 min by accomplishing 98% of removal ratio. Moreover, chemical adsorption via boronate affinity mainly dominate the binding process and catechol is homogenously captured onto the binding sites with uniform distribution by a monolayer adsorption. Furthermore, 87.97% of catechol is captured after the effective mixing and selective enrichment by MI-SBSE by accelerating mass transfer. The findings of the present work not only provides insights to develop nanosheet-based stir bar using imprinted Janus nanosheets, but also presents a new method for catechol separation.

Molecularly Imprinted Stir Bar Sorptive Extraction Coupled with High‑Performance Liquid Chromatography for Trace Analysis of Diclofenac in Different Real Samples

A novel molecularly imprinted polymer-coated stir bar has been used to selectively extract diclofenac (DFC) directly from real samples. DFC was used as template molecule for preparation of MIP coating. The effect of different parameters on the extraction efficiency were studied and the optimum conditions were established as: the absorption and desorption times were fixed at 10 min, stirring speed was 600 rpm, pH was adjusted to 5.1, the amount of NaCl was 0.35 mol/L and extraction process was performed at a temperature of 45 °C. Under the optimum conditions, the linear range of method was 0.5- 500.0 µg/L for DFC and the detection limit was calculated to be 0.15 µg/L with an enrichment factor of 242 folds. The technique was successfully applied for the analysis of trace amounts of DFC in seawater and commercial tablet samples. The mean recoveries of spiking real samples with DFC at 10.0 µg/L level were between 94.2-100.0 % with a mean RSD of 0.7-4.6%.

Response Surface Methodology of Pre-Concentration of Chorophenols from Seawater Samples by Molecularly Imprinted Stir Bar Sorptive Extraction Combined with HPLC: Box-Behnken Design.

A novel molecularly imprinted polymer coated stir bar was prepared using 2-chlorophenol (2-CP) as template molecule and used for selective extraction of phenolic compounds including chlorophenols (CPs) directly from seawater samples. Various parameters affecting extraction have been evaluated using one variable-at-a-time and Box-Behnken design. A three-level Box-Behnken experimental design by six factors, which combined the response surface methodology, was used to optimize the selective extraction of the CPs. Six independent variables, including the absorption and desorption times (ranging from 15 to 25 min), stirring speed (ranging from 550 to 650 rpm), pH of solution (ranging from 4.0 to 6.0), amount of NaCl (ranging from 0.30 to 0.40 mol/L) and temperature of extraction process (ranging from 40 to 50°C) were coded as A, B, C, D, E and F at three various levels (-1, 0 and 1). Under the optimum conditions, the detection limits calculated were 0.17, 0.33 and 0.38 μg/L, respectively, for 2-CP, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The linear ranges of method were 1.0-100.0 μg/L for all CPs studied. This method was employed for the direct extraction and determination of three CPs in seawater samples.

Determination of β-Agonist Residues in Animal-Derived Food by a Liquid Chromatography-Tandem Mass Spectrometric Method Combined with Molecularly Imprinted Stir Bar Sorptive Extraction.

A novel clenbuterol molecularly imprinted polymer (MIP)-coated stir bar was prepared and applied to the determination of six β-agonists in animal-derived food. Characterization and various parameters affecting adsorption and desorption behaviours were investigated. The extraction capacities of clenbuterol, salbutamol, ractopamine, mabuterol, brombuterol, and terbutaline for MIP coating were 3.8, 2.9, 3.1, 3.5, 3.2, and 3.3 times higher, respectively, than those of the NIP coating, respectively. The method of MIP-coated SBSE coupled with HPLC-MS/MS was developed. The recoveries in pork and liver samples were 75.8–97.9% with RSD from 2.6 to 5.3%. Limits of detection (LODs) and limits of quantification (LOQs) were 0.05–0.15 μg/kg and 0.10–0.30 μg/kg, respectively. Good linearities were obtained for six β-agonists with correlation coefficients (R 2) higher than 0.994. These results indicated the superiority of the proposed method in the analysis of β-agonists in a complex matrix.

Determination of semicarbazide in fish by molecularly imprinted stir bar sorptive extraction coupled with high performance liquid chromatography

A novel molecularly imprinted stir bar (MI-SB) for sorptive extraction of semicarbazide (SEM) was prepared in present paper. The coating of the stir bar was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, dynamic adsorption and static adsorption tests. The saturated adsorption of MI-SB was about 4 times over that of non-imprinted stir bar (NI-SB). The selectivity of MI-SB for SEM was much better than NI-SB. A method to determine SEM was established by coupling MI-SB sorptive extraction with HPLC-UV. The liner range was 1–100ng/mL for SEM with a correlation coefficient of 0.9985. The limit of detection was about 0.59ng/mL, which was below the minimum required performance limit of SEM in meat products regulated by European Union. The method was applied to the determination of SEM in fish samples with satisfactory results.

Determination of semicarbazide in fish by molecularly imprinted stir bar sorptive extraction coupled with high performance liquid chromatography

Determination of semicarbazide in fish by molecularly imprinted stir bar sorptive extraction coupled with high performance liquid chromatography

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.

Determination of melamine in powdered milk by molecularly imprinted stir bar sorptive extraction coupled with HPLC

A novel molecularly imprinted stir bar (MIP-SB) was developed with melamine (MA) as the template molecule in this study. The sorptive capacity of MIP-SB was nearly three times over that of non-imprinted stir bar (NIP-SB). The MIP-SB presented much better selectivity than NIP-SB when used to absorb MA and its analogues. An analytical method to determine MA in powdered milk was established by combining MIP-SB sorptive extraction with HPLC. The liner range was 0.0631–12.6ng/mL with good correlation coefficient of 0.9983, and the limit of detection was 0.0127ng/mL based on three times ratio of signal to noise. This method was successfully applied to the determination of MA in powdered milk with satisfactory results. The method built is simple and suitable for the determination of MA in milk products which is of great significance for quality control of milk products.

Novel molecularly imprinted stir bar sorptive extraction based on an 8-electrode array for preconcentration of trace exogenous estrogens in meat

A novel 8-electrode array as stir bar was designed for selective extraction of trace level exogenous estrogens from food samples, followed by liquid desorption and HPLC-photodiode array detection. The array consisted of 8 screen-printed electrodes and each electrode was modified with Fe3O4@meso-/macroporous TiO2 microspheres and molecularly imprinted film (m-TiMIF). The fabrication of the imprinted film coating was very simple without organic solvents and chemical grafting. Both bisphenol A (BPA) and diethylstilbestrol (DES) were employed as templates in m-TiMIF fabrication in order to enrich both targets simultaneously. Interestingly, the imprinted stir bar array showed higher extraction capacity and selectivity for BPA and DES than the non-imprinted counterpart. Meanwhile, it exhibited fast adsorption and desorption kinetics due to increased mass transport in the ultra-thin film. Importantly, the m-TiMIF coating was robust enough for at least 20 uses without obvious alteration in extraction performance. The main parameters affecting the extraction efficiency, including stir speeding, sample pH, ionic strength, extraction time, desorption solvent and time, were optimized. Under optimal experimental conditions, the limits of detection (S/N=3) of the developed method were 0.28 and 0.47μgL−1 for BPA and DES respectively, with enrichment factors of 32.6 and 52.8-fold. The linear ranges were 3.0–1500μgL−1 and 4.0–1500μgL−1 for BPA and DES, respectively. The m-TiMIF-coating conferred better recovery and selectivity, compared with the commercial stir bar coating. The new method was successfully applied to assess BPA and DES in pork and chicken samples with satisfactory recovery.

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.

Molecularly Imprinted Polymers for the Analysis of Environmental Estrogen Bisphenol A

Molecularly imprinted polymer (MIP) has the characteristics of predetermination, specific recognition and practicability. It can eliminate the interference of complicated matrix. It has been widely used as selective adsorption material in sample preparation. Bisphenol A is a common endocrine disruptor in environment. Its toxic effects and analysis have attracted widespread concern. In this paper, the molecularly imprinted sample preparation techniques for bisphenol A were comprehensively reported, including molecularly imprinted microspheres extraction, molecularly imprinted solid phase extraction, molecularly imprinted solid phase microextraction, molecularly imprinted stir bar sorptive extraction and molecularly imprinted membrane extraction. Moreover, the trends of BPA-molecularly imprinted techniques are prospected.

Highly selective and sensitive analysis of dopamine by molecularly imprinted stir bar sorptive extraction technique coupled with complementary molecularly imprinted polymer sensor

This paper reports a combination of molecularly imprinted stir bar sorptive extraction and complementary molecularly imprinted polymer-sensor for the analysis of dopamine as a biomarker of several neurodegenerative diseases occurred at ultra trace level. This exploited iniferter initiated polymerization via “surface grafting-from” approach onto magnetic stir bar (for sorptive extraction) and multiwalled carbon nanotubes-ceramic electrode (for detection). Such hyphenation helped dual pre-concentration of dopamine in aqueous, biological and pharmaceutical samples. This enabled high sensitivity to achieve the stringent limit [limit of detection: 4.9ngL−1, RSD=2.4%, S/N=3, cerebrospinal fluid] of clinical detection, without any problems of non-specific contributions and cross-reactivity.

Molecularly imprinted stir bar sorptive extraction coupled with atomic absorption spectrometry for trace analysis of copper in drinking water samples

In this work, a novel molecularly imprinted polymer (MIP) coated stir bar was fabricated and used for the extraction of trace amounts of Cu from drinking water. Cu–morin complex was used as template molecule which was chemically bonded to a glass stir bar and was employed for stir bar sorptive extraction of trace amounts of copper ions. The effects of different parameters such as pH, adsorption and desorption time, stirring rate, temperature and amount of ligand (morin) were evaluated on the extraction efficiency and the optimum conditions were established: the extraction and desorption times were fixed respectively at 20 and 30 min, mole ratio of ligand to the analyte was selected as 2, stirring speed was 700 rpm, pH was adjusted to 5 and the extraction process was performed at a temperature of 45 °C. Under these conditions, a pre-concentration factor of 25 was achieved and the total capacity of the stir bar for copper uptake was found to be 1200 μg. A non-imprinted polymer coating was used for comparison. The MIP stir bar showed sufficient mechanical and chemical stability and was able to perform more than 50 extractions without any damage to the polymer phase. The reproducibility between stir bars (n = 5) was 8.9%. The detection limit of the proposed method was found to be 0.38 μg L−1 with a relative standard deviation within 0.56–5.3% and a dynamic range between 1 and 1000 μg L−1. The method was successfully applied to the pre-concentration and determination of copper in a few different water samples.

Online desorption of molecularly imprinted stir bar sorptive extraction coupled to high performance liquid chromatography for the trace analysis of triazines in rice

Based on a special homemade interface, the molecularly imprinted stir bar sorptive extraction was coupled to high performance liquid chromatography for the online desorption and analysis. During desorption, the analytes desorbed from stir bar were delivered to a sample loop and then was introduced into liquid chromatography for further analysis. The online desorption and introduction processes were real-time monitored by the ultraviolet detector of the liquid chromatography system. In this way, the method sensitivity and reproducibility was improved for the introduction timing of the desorption solvent with greatest concentration of the target analytes was accurately controlled. To demonstrate the feasibility of the method, terbuthylazine imprinted stir bar was synthesized and used for the analysis of nine triazines in rice. Under the optimized conditions, limits of detection of 0.02-0.11 μg/L and precision within 4.3-7.2% were achieved. The new method was compared with other two traditional offline desorption procedures, i.e. ultrasonic-assisted desorption and static thermal desorption. The comparison results showed that the proposed method is accurate, precise, fast, and suitable for the trace analysis of complex samples.

Preparation of Trimethoprim Molecularly Imprinted Stir Bar Sorptive Extraction and Its Application for Trace Analysis of Trimethoprim and Sulfonamides in Complex Samples

Abstract Trimethoprim molecularly imprinted polymer (MIP) was prepared as the coating of stir bar sorptive extraction (SBSE) and applied to the trace analysis of trimethoprim and three sulfonamides in complex samples. The MIP-coating was about 21.5 μm thickness with the relative standard deviations (RSD) of 5.9% ( n = 10). It was homogeneous and dense with good thermal and chemical stability. The extraction capability of the MIP-coating was 1.7 times over that of the non-imprinted polymer (NIP) coating. The MIP-coating exhibited selective adsorption ability to sulfonamides, triazines and methotrexate besides antibacterial synergists. The methods for the determination of trimethoprim and three sulfonamides by MIP-coated stir bar sorptive extraction coupled with HPLC were developed. It was successfully applied to the trace trimethoprim analysis in spiked urine and plasma samples. The linear range was 5-200 μg L −1 and the detection limit was 1.6 μg L −1 . The recoveries in urine and plasma samples were 84.5% to 91.7% with RSDs of 2.9%–4.4%, 71.9% to 85.1% with RSDs of 3.0%–7.3%, respectively. The trimethoprim MIP-coated stir bar was also applied to the trace sulfonamides analysis in spiked milk sample. The linear range was 10–200 μg L −1 , the detection limit was within the range of 4.5–6.1 μg L −1 , and the recovery was 83.2%–110.2% with RSDs of 4.1%–8.0%.

Determination of ractopamine in pork by using electrochemiluminescence inhibition method combined with molecularly imprinted stir bar sorptive extraction

Ractopamine (RAC) was observed to quench the electrochemiluminescence (ECL) of Ru ( bpy ) 3 2 + –DBAE system at a glassy carbon electrode (GCE). Based on the ECL signal changes, a detection method for RAC in pork was established. Under the optimized conditions, the linear range is from 1.0 × 10 −10 to 5.0 × 10 −8 mol L −1, and the detection limit is 3.5 × 10 −12 mol L −1, which are better than other previously reported methods. Molecularly imprinted polymer (MIP) was synthesized as coating of the stir bar sorptive extraction (SBSE), and MISBSE was used for the selective extraction and purification of RAC in real samples. The ECL method combined with MISBSE pre-treatment was applied for determination of RAC in pork, and the result was satisfactory with the recoveries being 99.7–115.0% and the RSDs being <5% respectively. A possible mechanism of Ru ( bpy ) 3 2 + –DBAE/RAC system was proposed based on UV absorption spectra, cyclic voltammograms and I ECL– E curves.

Molecularly imprinted stir bar sorptive extraction coupled with high performance liquid chromatography for trace analysis of sulfa drugs in complex samples

A novel sulfamethazine molecularly imprinted polymer (MIP)-coated stir bar for sorptive extraction of eight sulfa drugs from biological samples was prepared. The MIP-coating was about 20μm thickness with the relative standard deviation (RSD) of 6.7% (n=10). It was characterized by scanning electron microscope, infrared spectrum, thermogravimetric analysis, and solvent-resistant investigation, respectively. The non-imprinted polymer (NIP)-coating was used for comparison. The adsorptive capacity and selectivity of MIP-coating were evaluated in detail. The MIP-coating showed higher adsorption capability and selectivity than the NIP-coating. The saturated adsorption amount of the MIP-coating was 4.6 times over that of the NIP-coating in toluene. Sulfamethazine could be detected after the MIP-coated stir bar sorptive extraction even at a low concentration of 0.2μg/L. The MIP-coating also exhibited selective adsorption ability to analogues of the template. A method for the determination of eight sulfa drugs in biological samples by MIP coated stir bar sorptive extraction coupled with high performance liquid chromatography (HPLC) was developed. The extraction conditions, including extraction solvent, extraction time, desorption solvent, desorption time and stirring speed, were optimized. The linear ranges were 1.0–100μg/L and 2.0–100μg/L for eight sulfonamides, respectively. The detection limits were within the range of 0.20–0.72μg/L. The method was successfully applied to simultaneous multi-residue analysis of eight sulfonamides in spiked pork, liver and chicken samples with the satisfactory recoveries.

Investigation of ractopamine molecularly imprinted stir bar sorptive extraction and its application for trace analysis of β 2-agonists in complex samples

In this paper, a novel molecularly imprinted polymer (MIP) coated stir bar with ractopamine as template by glass capillary filling with magnetic core as substrate was prepared reproducibly. The ractopamine MIP coating was homogeneous and porous with the average thickness of 20.6 μm. The extraction apparatus for the stir bar was improved to avoid coating loss. The MIP-coated stir bar showed better extraction capacity and good selectivity than that of non-imprinted polymer (NIP) coated stir bar to ractopamine and its analogues. The extraction capacities of ractopamine, isoxsuprine, clenbuterol and fenoterol for MIP-coated stir bar were 3.3, 3.1, 2.8 and 2.4 times as much as that of the NIP coated stir bar, respectively. The MIP-coated stir bars could be used at least 40 times without apparent damage and kept in dried air for 8 months without reduce of extraction ability. A method for the determination of β 2-agonists in complex samples by MIP-coated stir bar sorptive extraction coupled with high-performance liquid chromatography (HPLC) was developed. The linear ranges were 0.5–40 μg/L for ractopamine and 1.0–40 μg/L for isoxsuprine and clenbuterol. The detection limits were within the range of 0.10–0.21 μg/L. The method was successfully applied to the analysis of β 2-agonists in spiked pork, liver and feed samples with the recoveries of 83.7–92.3%, 80.5–90.2% and 73.6–86.2%, respectively. The RSDs was within 2.9–8.1%. The method is very suitable for the determination of trace β 2-agonists in pork, liver and feed samples.