Solid-phase extraction of tramadol from plasma and urine samples using a novel water-compatible molecularly imprinted polymer

In this study, a novel method is described for the determination of tramadol in biological fluids using molecularly imprinted solid-phase extraction (MISPE) as the sample clean-up technique combined with high-performance liquid chromatography (HPLC). The water-compatible molecularly imprinted polymers (MIPs) were prepared using methacrylic acid as functional monomer, ethylene glycol dimethacrylate as cross-linker, chloroform as porogen and tramadol as template molecule. The novel imprinted polymer was used as a solid-phase extraction (SPE) sorbent for the extraction of tramadol from human plasma and urine. Various parameters affecting the extraction efficiency of the polymer have been evaluated. The optimal conditions for the MIP cartridges were studied. The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of tramadol. The limit of detection (LOD) and limit of quantification (LOQ) for tramadol in urine samples were 1.2 and 3.5 μg L⁻¹, respectively. These limits for tramadol in plasma samples were 3.0 and 8.5 μg L⁻¹, respectively. The recoveries for plasma and urine samples were higher than 91%.     

Application of Factorial Design and Box–Behnken Matrix in the Optimization of a Magnetic Nanoparticles Procedure for Copper Determination in Water and Biological Samples

This study describes the development by response surface methodology (RSM) of a procedure for copper determination by inductively coupled plasma optical emission spectrometry (ICP-OES) in water and biological samples after extraction by magnetic nanoparticles. Four variables such as, pH of solution, amount of extractant, amount of nanoparticles, and time were regarded as factors in the optimization study. Results of the two-level full factorial design (2⁴) based on an analysis of variance demonstrated that only the pH, amount of extractant (E), and amount of nanoparticles (N) were statistically significant. Optimal conditions for the extraction of copper samples were obtained by using Box–Behnken design. Optimum conditions were 5.1, 7.2 mg, and 9.6 mg, for pH of solution, amount of nanoparticles, and amount of extractant, respectively. Under the optimized experimental conditions, the detection limit of the proposed method followed by ICP-OES was found to be 0.9?µg L^?1. The method was applied to the determination of copper in water and biological samples.     

Molecularly imprinted electrochemiluminescence sensor based on ZIF-8 doped with CdSe quantum dots for the detection of trace estriol

A composite of the metal–organic framework compound ZIF-8 doped with CdSe quantum dots (QDs) with sensitive and stable luminescence was synthesized, and a molecularly imprinted electrochemiluminescence (ECL) sensor was constructed based on this composite. The ZIF-8@CdSe molecularly imprinted ECL sensor combines the high sensitivity of ECL and the high selectivity of molecular imprinting to realize the sensitive and specific detection of estriol. CdSe QDs and gold nanoparticles were encapsulated within ZIF-8 to obtain the ZIF-8@CdSe QDs/GNP (ZIF@CdSe/GNP) composite. Subsequently, the GNPs were further loaded on the surface of this composite to obtain the GNP/ZIF@CdSe/GNP composite. l -Cysteine was used to immobilize the GNP/ZIF@CdSe/GNP composite on the surface of a gold electrode to obtain the GNP/ZIF@CdSe/GNP-modified gold electrode. A molecularly imprinted polymer (MIP) film was prepared on the surface of the modified electrode by electropolymerization with o-phenylenediamine as the functional monomer and estriol as the template molecule. After elution, estriol could be specifically recognized by the cavities. The readsorption of estriol by the MIP can prevent the coreactant from reaching the electrode surface through the cavities, thereby weakening ECL. A good linear relationship existed between the ∆ECL and lg C of estriol concentrations of 1 × 10⁻¹⁴ to 1 × 10⁻⁹ mol·L⁻¹. The detection limit was as low as 8.9 × 10⁻¹⁶ mol·L⁻¹. The sensor was applied in the determination of estriol in serum samples with a recovery of 97.0–102%.     

Highly selective determination of phenolphthalein by flow injection chemiluminescence method based on a molecular imprinting polymer

The phenolphthalein‐imprinted polymer was prepared with methacrylic acid as functional monomer and ethylene glycol dimethacrylate as cross‐linker. Taking advantage of the quenching effect of phenolphthalein on the potassium permanganate–HCl–anhydrous alcohol chemiluminescence system, a new model was established to determine phenolphthalein by a highly selective flow injection chemiluminescence method. The traditional flow‐though cell was replaced with a novel flow path using a Y‐shaped polymethyl methacrylate column, through which the three reactants were injected simultaneously. The linear range of this assay was from 1.0 × 10^?8 to 1.0 × 10^?6 g/mL (r = 0.9978). The limit of detection was 8.9 × 10^?9 g/mL. The relative standard deviation for the determination of 1.0 × 10^?8 g/mL phenolphthalein solution was below 2.9% (n = 11). The proposed method was applied to the determination of phenolphthalein in real samples with satisfactory results. Copyright © 2009 John Wiley & Sons, Ltd.     

Class-specific molecularly imprinted polymers for the selective extraction and determination of sulfonylurea herbicides in maize samples by high-performance liquid chromatography–tandem mass spectrometry

A novel method based on the molecularly imprinted solid-phase extraction (MISPE) procedure has been developed for the simultaneous determination of concentrations of sulfonylurea herbicides such as chlorsulfuron (CS), monosulfuron (MNS), and thifensulfuron methyl (TFM) in maize samples by liquid chromatography–tandem quadrupole mass spectrometry (LC–MS/MS). The molecularly imprinted polymer (MIP) for sulfonylurea herbicides was synthesized by precipitation polymerization using chlorsulfuron as the template molecule, 2-(diethylamino)ethyl methacrylate (DEAMA) as the functional monomer, and trimethylolpropane trimethacrylate (TRIM) as the cross-linker. The selectivities of the chlorsulfuron template and its analogs on the molecularly imprinted polymer were evaluated by high-performance liquid chromatography (HPLC). The extraction and purification procedures for the solid-phase extraction (SPE) cartridge with a molecularly imprinted polymer as the adsorbent for the selected sulfonylurea herbicides were then established. A molecularly imprinted solid-phase extraction method followed by high-performance liquid chromatography–tandem mass spectrometry for the determination of chlorsulfuron, monosulfuron, and thifensulfuron methyl was also established. The mean recoveries of these compounds in maize were in the range 75–110% and the limits of detection (LOD) of chlorsulfuron, monosulfuron, and thifensulfuron methyl were 0.02, 0.75, and 1.45 μg kg⁻¹, respectively. It was demonstrated that the MISPE–HPLC–MS/MS method could be applied to the determination of chlorsulfuron, monosulfuron, and thifensulfuron methyl in maize samples.     

Task-specific ionic liquid-assisted extraction and separation of astaxanthin from shrimp waste

Astaxanthin, as an outstanding antioxidant reagent, was successfully extracted from shrimp waste by the ionic liquids based ultrasonic-assisted extraction. Seven kinds of imidazolium ionic liquids with different cations and anions were investigated in this work and one task-specific ionic liquid in ethanol with 0.50 mol L⁻¹ was selected as the solvent. At the optimized ultrasonic extraction conditions, the extraction amount of astaxanthin increased 98% (92.7 μg g⁻¹) compared to the conventional method (46.7 μg g⁻¹). Furthermore, the extracted solution was isolated through the solid-phase extraction with a molecularly imprinted polymer sorbent. After loading the samples on molecularly imprinted polymer cartridge, the different washing and elution solvents, such as water, methanol, n-hexane, acetone and dichloromethane, were evaluated, and finally, astaxanthin was separated from the shrimp waste extract.     

Synthesis of nano‐sized hydrogen phosphate‐imprinted polymer in acetonitrile/water mixture and its use as a recognition element of hydrogen phosphate selective all‐solid state potentiometric electrode

Herein, a new recipe is introduced for the preparation of hydrogen phosphate ion‐imprinted polymer nanoparticles (nano‐IIP) in acetonitrile/water (63.5:36.5) using phosphoric acid as the template. The nano‐IIP obtained was used as the recognition element of a carbon paste potentiometric sensor. The IIP electrode showed a Nernstian response to hydrogen phosphate anion; whereas, the non‐imprinted polymer (NIP)‐based electrode had no considerable sensitivity to the anion. The presence of both methacrylic acid and vinyl pyridine in the IIP structure, as well as optimization of the functional monomers‐template proportion, was found to be important to observe the sensing capability of the IIP electrode. The nano‐IIP electrode showed a dynamic linear range of 1 × 10^?5‐1 × 10^?1 mol L‐1, Nernstian slope of 30.6 ± (0.5) mV decade ^?1, response time of 25 seconds, and detection limit of 4.0 × 10^?6 mol L^?1. The utility of the electrodes was checked by potentiometric titration of hydrogen phosphate with La³⁺ solution.     

Molecularly imprinted polymer for analysis of zidovudine and stavudine in human serum by liquid chromatography–mass spectrometry

A molecularly imprinted polymer (MIP) using zidovudine (AZT) as template and methacrylic acid as monomer was prepared. The synthesis of the MIP was performed in acetonitrile. The synthesized material was then tested for the solid-phase extraction of AZT from different media (pure organic solvents and hydro-organic mixtures). An optimised procedure was developed for the selective extraction of AZT with a recovery of 96% using the MIP and only 3% on a non-imprinted polymer used as control polymer. A specific capacity of 0.2 μmol g^?1 was determined. The specificity of the MIP was evaluated by studying the retention behaviour of two others nucleoside analogues. The feasibility of the MIP to selectively extract AZT and stavudine (d4T) from human serum was also demonstrated with recoveries of 80 and 85% respectively. The lower limit of quantification (LLOQ) and the lower limits of detection (LLOD) for AZT were 5.10^?7 and 10^?7 M respectively.     

Synthesis and evaluation of a selective molecularly imprinted polymer for the contraceptive drug levonorgestrel

A molecularly imprinted polymer (MIP) has been prepared using levonorgestrel (LEV) as template. The polymer was synthesised in a non-covalent approach using methacrylic acid (MAA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as cross-linking monomer via a free radical polymerization. An equivalent blank polymer was also synthesised in the absence of the template compound. Batch adsorption experiments were used to evaluate the binding affinity of the imprinted polymer. After packing MIP into a stainless steel column (150 mm x 4.6 mm i.d.), retention and elution of the template and related compounds were evaluated by high-performance liquid chromatography (HPLC). This LEV imprinted polymer was further applied for selective solid phase extraction (SPE) of LEV from human serum. It was confirmed that the binding ability of the prepared MIP for LEV was essentially sufficient in the presence of other compounds coexisting in serum sample. Therefore, as a selective and efficient solid phase material, LEV imprinted polymer has a high potential application in analysis of this steroidal hormone in clinical purposes.     

Chiral determination of cinchonine using an electrochemiluminescent sensor with molecularly imprinted membrane on the surfaces of magnetic particles

A novel molecular imprinting electrochemiluminescence sensor for detecting chiral cinchonine molecules was developed with a molecularly imprinted polymer membrane on the surfaces of magnetic microspheres. Fe₃O₄@Au nanoparticles modified with 6‐mercapto‐beta‐cyclodextrin were used as a carrier, cinchonine as a template molecule, methacrylic acid as a functional monomer and N ,N ′‐methylenebisacrylamide as a cross‐linking agent. Cinchonine was specifically recognized by the 6‐mercapto‐beta‐cyclodextrin functional molecularly imprinted polymer and detected based on enhancement of the electrochemiluminescence intensity caused by the reaction of tertiary amino structures of cinchonine molecules with Ru(bpy)₃²⁺. Cinchonine concentrations of 1 × 10^?10 to 4 × 10^?7 mol/L showed a good linear relationship with changes of the electrochemiluminescence intensity, and the detection limit of the sensor was 3.13 × 10^?11 mol/L. The sensor has high sensitivity and selectivity, and is easy to renew. It was designed for detecting serum samples, with recovery rates of 98.2% to 107.6%.     

Determination of phenformin hydrochloride using molecular imprinting technology coupled with flow-injection chemiluminescence

A novel method was developed using molecular imprinting technology (MIT) coupled with flow‐injection chemiluminescence (FI‐CL) for highly sensitive detection of phenformin hydrochloride (PH). The phenformin imprinted polymer was synthesized with methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate (EGDMA) as a cross‐linker. Newly synthesized molecularly imprinted polymer (MIP) particles were packed into a column as a selective recognition element for determination of PH. A CL method for the determination of PH was developed based on the CL reaction of PH with N‐bromosuccinimide sensitized by eosin Y in basic media. The optimization of detection conditions was investigated. The CL intensity responded linearly to the concentration of PH in the range 0.09–2.0 µg/mL, with a correlation coefficient of 0.9920. The detection limit was 0.031 µg/mL. The relative standard deviation for the determination of 1.0 µg/mL PH solution was 1.0% (n = 11). The method was applied to the determination of PH in urine samples, with satisfactory results. Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of nicotine,anabasine, and cotinine in urine and saliva samples using single-drop microextraction

A simple, sensitive, and inexpensive singe-drop microextraction (SDME) followed by gas chromatography and flame-ionization detection (GC-FID) was developed for determination of nicotine, anabasine, and cotinine in human urine and saliva samples. The target compounds were extracted from alkaline aqueous sample solution into an organic acceptor drop suspended on the tip of a 25-μL GC microsyringe in the aqueous sample solution. This microsyringe was also used for direct injection after extraction. Under optimized experimental conditions, calibration plots were found to be linear in the range of 0.5–25.0, 0.5–65.0, and 0.5–45.0 mg L^?1 for nicotine, anabasines and cotinine, respectively. The method detection limit values were in the range of 0.33–0.45 mg L^?1. Intra-day and inter-day precisions for peak area ratios were in the range of 1.3–9.2% and 2.0–7.0%, respectively. The proposed procedure was successfully applied to the determination of analytes in spiked urine and saliva samples with satisfactory results. The mean relative recoveries of spiked water samples ranged over 71.2–111.0%, with relative standard deviations varying from 2.3% to 10.0%.     

PREPARATION OF GLUTATHIONE IMPRINTED POLYMER

Glutathione imprinted polymer was prepared using 1-vinyl imidazole and ethylene glycol dimethacrylate as the functional monomer and crosslinker, respectively, in dimethyl sulfoxide. The adsorption selectivity of glutathione-imprinted polymer was tested by reduced glutathione, oxidized glutathione, and L-Gly-Leu-Tyr in 30% phosphate buffer (0.01 M, pH 5.0)–70% acetonitrile and binding affinity values were compared. Reusability of molecularly imprinted polymer particles was also investigated. Molecularly imprinted polymer particles were found to be stable and to maintain glutathione adsorption capacity at 95% when washed with methanol–acetic acid (10%) after seven usages. Functional monomer 1-vinyl imidazole and cross linker ethylene glycol dimethacrylate-based glutathione imprinted polymer could be used as solid phase extraction material for recognition of glutathione in biological samples.     

Molecularly imprinted microspheres as SPE sorbent for selective extraction of four Sudan dyes in catsup products

A highly selective molecularly imprinted solid-phase extraction (MISPE) coupled with high performance liquid chromatography (HPLC) ultraviolet-visible detection was developed for the simultaneous isolation and determination of four Sudan dyes (I, II, III and IV) in catsup products. The novel molecularly imprinted microspheres (MIM) were synthesized by aqueous suspension polymerization using phenylamine and naphthol as template, which showed high affinity to Sudan dyes in aqueous solution. In order to develop a selective extraction protocol for simultaneous determination the four Sudan dyes from catsup products, the molecular recognition properties of MIM as a SPE sorbent were evaluated. Under the optimized condition, good linearity was obtained from 0.01 to 2.5 μg g(-1) (r(2)≥ 0.9990) with the relative standard deviations of less than 3.4%. This proposed MISPE-HPLC procedure eliminated the effect of template leakage on quantitative analysis and could be applied to direct determination of four Sudan dyes in complicated food samples.     

Simultaneous speciation of chromium by spectrophotometry and multicomponent analysis

Abstract

A simple, fast and sensitive spectrophotometric method for the simultaneous determination of Cr(III) and Cr(VI) in effluents and contaminated waters using a UV-visible spectrophotometer, which operates with an advanced software for multicomponent analysis, is proposed. The method consists in the complexation of Cr (III) with EDTA and reaction of Cr(VI) with diphenylcarbazide (DPC). Variables, such as pH and colour stability time, were studied. The effect of concomitant ions on the simultaneous Cr(III) and Cr(VI) determination was also investigated. The sums of the chromium species concentrations obtained by the proposed method were compared with the total chromium concentrations found by electrothermal atomic absorption spectrometry. Recoveries of the chromium species between 75 and 136% were obtained for spiked samples. The linear working range for Cr(III) was 0.5-30 mg L^?1, while for Cr(VI) was 0.005-0.30 mg L^?1. The detection limits were 0.3 mg L^?1 for Cr(III) and 0.003 mg L^?1 for Cr(VI) while the quantification limits were 1.0 mg L^?1 for Cr(III) and 0.01 mg L^?1 for Cr(VI).     

A novel reductive graphene oxide‐based magnetic molecularly imprinted poly(ethylene‐co‐vinyl alcohol) polymers for the enrichment and determination of polychlorinated biphenyls in fish samples

The novel reductive graphene oxide‐based magnetic molecularly imprinted poly(ethylene‐co‐vinyl alcohol) polymers (rGO@m‐MIPs) were successfully synthesized as adsorbents for six kinds of polychlorinated biphenyls (PCBs) in fish samples. rGO@m‐MIPs was prepared by surface molecular imprinting technique. Besides, Fe₃O₄ nanoparticles (NPs) were employed as magnetic supporters, and rGO@Fe₃O₄ was in situ synthesis. Different from functional monomer and cross‐linker in traditional molecularly imprinted polymer, here, 3,4‐dichlorobenzidine was employed as dummy molecular and poly(ethylene‐co‐vinyl alcohol) was adopted as the imprinted polymers. After morphology and inner structure of the magnetic adsorbent were characterized, the adsorbent was employed for disperse solid phase extraction toward PCBs and exhibited great selectivity and high adsorption efficiency. This material was verified by determination of PCBs in fish samples combined with gas chromatography‐mass spectrometry (GC‐MS) method. According to the detection, the low detection limits (LODs) of PCBs were 0.0035–0.0070 µg l⁻¹ and spiked recoveries ranged between 79.90 and 94.23%. The prepared adsorbent can be renewable for at least 16 times and expected to be a new material for the enrichment and determination of PCBs from contaminated fish samples. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemiluminescence sensor for sulfonylurea herbicide using molecular imprinted microspheres as recognition element

Uniform molecular imprinting microspheres were prepared using precipitation polymerization with thifensulfuron‐methyl (TFM) as template, acrylamide as functional monomer and ethylene glycol dimethacrylate as cross‐linker. TFM could be selectively adsorbed on the molecularly imprinted polymers (MIPs) matrix through the hydrogen bonding interaction and the adsorbed TFM could be sensed by its strikingly enhancing effect on the weak chemiluminescence (CL) reaction between luminol and hydrogen peroxide. On this basis, a novel CL sensor for the determination of TFM using MIPs as recognition elements was established. The logarithm of net CL intensity (ΔI) is linearly proportional to the logarithm of TFM concentration (C) in the range from 1.0 × 10^?9 to 5.0 × 10^?5 mol L^?1 with a detection limit of 8.3 × 10^?10 mol L^?1 (3σ). The results demonstrated that the MIP–CL sensor was reversible and reusable and that it could strikingly improve the selectivity and sensitivity of CL analysis. Furthermore, it is suggested that the CL enhancement of luminol–H₂O₂ by TFM might be ascribed to the enhancement effect of CO₂, which came from TFM hydrolysis in basic medium. Copyright © 2010 John Wiley & Sons, Ltd.     

Room temperature synthesis and binding studies of solution‐processable histamine‐imprinted microspheres

Accurate quantification of histamine levels in food and in biological samples is important for monitoring the quality of food products and for the detection of pathophysiological conditions. In this study, solution processable histamine‐imprinted microspheres were synthesized at 30°C via dilute free radical phototochemical polymerization technique using ethylene glycol dimethacrylate (EGDMA) as the crosslinker and methacrylic acid (MAA) as the monomer. The processability of the resulting polymer is dictated by the monomer feed concentration (eg, 4 wt% 80:20 EGDMA:MAA formulation) and solvent (acetonitrile). Whereas, the particle size is influenced by the monomer feed concentration, the presence of template molecule, and independent of the crosslinker content. Evaluation of the binding performance of the photochemically imprinted polymers (PCP) with different crosslinker content (80 and 90 wt%) indicated that the selective binding capacity was notably higher in PCP‐80 (N= 16.0 μmol/g) compared to PCP‐90 (N= 10.1 μmol/g) when analyzed via frontal analysis capillary electrophoresis (FACE) using Freundlich isotherm. In addition, PCP‐80 microspheres are more selective toward histamine than conventional thermal polymers (CTP‐80) prepared at 60°C in the presence of structural analogs such as histidine, imidazole, and tryptamine under cross‐rebinding and competitive conditions. These results demonstrated that histamine‐selective imprinted polymers can be obtained readily using room temperature photochemical polymerization where these materials can be subsequently used as recognition element for optical‐based histamine sensing.     

The Use of Fungal Biomass Agaricus bisporus Immobilized on Amberlite XAD-4 Resin for the Solid-Phase Preconcentration of Thorium

Solid-phase extraction method was developed for the preconcentration of thorium (Th). Fungal biomass Agaricus bisporus was immobilized to Amberlite XAD-4 as solid-phase sorbent. The critical parameters such as pH of the sample solution, flow rate of the sample, volume of the sample, and the effect of major ions that affect the preconcentration of thorium in this system were evaluated. The optimum pH for the sorption of Th is 6.0, and quantitative elution occurs with 1.0 mol L^?1HCl. The loading capacity was determined as 0.079 mmol g^?1. The optimized method was validated through analysis of the certified reference material of tea leaves (NCS ZC73014) and successfully applied to the determination of Th in a real ore sample with satisfactory results.     

Utility of solid-phase spectrophotometry to determine trace amounts of zinc in environmental and biological samples

A solid-phase spectrophotometric analysis has been proposed for preconcentration and determination of Zn(II) in real samples. The procedure is based on sorption of zinc(II) as 5-(2-benzothiazolylazo)-8-hydroxyquinoline (BTAHQ) complex on dextran-type anion-exchange gel (Sephadex DEAE A-25). The influences of the analytical parameters, including pH of the aqueous solution, amounts of BTAHQ, and sample volume, were investigated. The absorbance of the gel at 675 and 750 nm, packed in a 1.0-mm cell, was measured directly. The molar absorptivities were found to be 2.50 × 10⁷ and 9.55 × 10⁷ L mol⁻¹ cm⁻¹ for 500 and 1000 ml, respectively. Calibration was linear over the range of 0.05–1.10 μg L⁻¹ with a relative standard deviation of less than 1.60% (n = 10). The detection and quantification limits of the 500-ml sample method were 12 and 40 ng L⁻¹ on using 50 mg. For the 1000-ml sample, the detection and quantification limits were 7.5 and 25 ng L⁻¹ using a 50-mg exchanger. Increasing the sample volume can enhance sensitivity. No considerable interferences were observed from other investigated anions and cations on the Zn(II) determination. The proposed method was applied to determine zinc in environmental samples, including natural water, food, certified reference materials, meat, and biological samples, comparing the results simultaneously with those obtained using a flame atomic absorption spectrophotometer, whereby the validity of the method was tested.