Polymer Solid-phase Extraction Research Articles

Tyramine detection using PEDOT:PSS/AuNPs/1-methyl-4-mercaptopyridine modified screen-printed carbon electrode with molecularly imprinted polymer solid phase extraction

Tyramine (4-hydroxyphenethylamine), which is a monoamine metabolized by monoamine oxidase (MAO), exists widely in plants, animals, fermented foods, and salted foods. The incidence of hypertension, or “cheese effect”, which is associated with a large dietary intake of tyramine while taking MAO inhibitors has been reported; therefore, the measurement of tyramine is an urgent concern. Herein, an efficient approach that integrates a molecular imprinting polymer for solid phase extraction (MISPE) technique with a sensitive electrochemical sensing platform (SPCE/PEDOT: PSS/AuNP/1-m-4-MP) for the quantification of tyramine is presented. Enhanced electrode conductivity was achieved sequentially by constructing a conductive polymer (PEDOT: PSS) on a screen-printed carbon electrode (SPCE), followed by electrodeposition with gold nanoparticles (AuNPs) and, finally, by modification with positively charged 1-methyl-4-mercaptopyridine (1-m-4-MP) using an Au–S bond. Tyramine was isolated selectively and pre-concentrated by the MISPE technique; electroanalysis that used differential pulse voltammetry (DPV) in NaOH (0.1M, pH 13) was conducted successively. Experimental parameters (such as modes of electrode modification, ratio of PEDOT: PSS, pH of electrolyte, time required for AuNP deposition, and 1-m-4-MP concentrations) that were associated with optimal detection conditions were evaluated also. We obtained a linear concentration range (5–100nM, R2=0.9939) with LOD and sensitivity at 2.31nM, and 3.11μAnM−1cm−2, respectively. The applicability of our technique was demonstrated by analyzing tyramine in spiked serum and milk. The feature of our newly developed analytical methods that coupled sample pre-treatment (sample clean-up and pre-concentration) with sensitive detection makes it a promising tool for quantifying of tyramine.

Recent advances and progress in the detection of bisphenol A.

Bisphenol A (BPA) is an important industrial chemical used as a plasticizer in polycarbonate and epoxy resins in the plastic and paper industries. Because of its estrogenic properties, BPA has attracted increasing attention from many researchers. This review focuses primarily on analytical methods for BPA detection that have emerged in recent years. We present and discuss the advantages and disadvantages of sample preparation techniques (e.g., solvent extraction, solid-phase extraction, molecularly imprinted polymer solid-phase extraction, and micro-extraction techniques) and analytical methods (e.g., liquid chromatography, liquid chromatography-mass spectrometry, gas chromatography-mass spectrometry, capillary electrophoresis, immunoassay, and several novel sensors). We also discuss expected future developments for the detection of BPA. Graphical Abstract This review focuses primarily on the recent development in the detection of bisphenol A including sample pre-treatment and analytical methods.

Molecularly imprinted polymer-high performance liquid chromatography for the determination of tetracycline drugs in animal derived foods

In this study, a molecularly imprinted polymer solid phase extraction method combining high performance liquid chromatography was developed to determine the residues of tetracycline drugs in animal derived foods. The polymer was synthesized with chlortetracycline as template molecule, methacrylic acid as functional monomer at template/monomer ratio of 1:4. The prepared solid phase extraction column was able to capture four tetracyclines simultaneously with high adsorption capacities (3560–4700 ng) and high recoveries (>87%), and was able to be reused for at least thirty times. The limits of detection were in a range of 20–40 ng/g, and the recoveries from fortified blank samples (milk, egg and pork) were in a range of 74%–93%. Furthermore, the polymer-based column achieved better purification effect than three commercial solid phase extraction columns. This is the first study reporting the use of chlortetracycline based molecularly imprinted polymer for determination of tetracyclines in animal derived foods.

Simultaneous preconcentration and determination of malachite green and fuchsine dyes in seafood and environmental water samples using nano-alumina-based molecular imprinted polymer solid-phase extraction

ABSTRACTMolecular imprinted polymer for determination of malachite green (MG) and fuchsine basic (FU) dyes by spectrophotometry has been used, to develop a novel simultaneous extraction and preconcentration method. Molecularly imprinted layer-coated nano-alumina (MIP@Nano-Al2O3) as adsorbent was prepared by surface molecular imprinting technique, and characterised by FTIR spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis (EDAX) and thermogravimetric analysis (TGA). The method is based on simultaneous extraction of MG and FU dyes from aqueous solution by using molecularly imprinted polymer and measuring the absorbance at 617 and 546 nm for MG and FU, respectively. Parameters which affect the extraction efficiency such as pH, volume of eluent and amount of adsorbent were investigated and optimised. Linear calibration curves were obtained in the range of 2–750 ng mL−1 for MG and 1–240 ng mL−1 for FU under optimum conditions. Detection limit based on three times the standard deviation of the blank (3Sb) was 0.655 and 0.245 ng mL−1 (n = 10) for MG and FU, respectively. The relative standard deviation (RSD) for 100 ng mL−1 of MG and FU was 2.35 and 3.06% (n = 7), respectively. The method was applied to the simultaneous determination of the dyes in different seafood and environmental water samples.

Trace residue analysis of dicyandiamide, cyromazine, and melamine in animal tissue foods by ultra-performance liquid chromatography

An effective sample preparation procedure using an accelerated solvent extraction (ASE) procedure, followed by cleaning with melamine molecularly imprinted polymers solid-phase extraction (MISPE) was developed. A novel and highly sensitive ASE–MISPE–ultra-performance liquid chromatography (UPLC) method was developed for effective separation and simultaneous determination of dicyandiamide (DCD), cyromazine (CYR), and melamine (MEL) in complex animal tissue foods. Under optimized conditions, good linearity was achieved with a correlation coefficient (r) of 0.9999 in the range of at least two orders of magnitude. The limit of quantification of the method was 1.7 μg/kg, 5.0 μg/kg, and 3.2 μg/kg for DCD, MEL, and CYR, which was three orders of magnitude smaller than the maximum residue limits (MRLs). The intra- and inter-day precisions (in terms of the relative standard deviation, RSD) of the three analytes were in the range of 1.7–3.1% and 3.1–6.3%, respectively. The average recoveries of analytes from blank chicken, beef, mutton, pork, and pig liver samples spiked with the three levels varied from 91.2% to 107% with RSD of 1.7–8.3% for DCD, 89.0–104% with RSD of 2.1–6.1% for CYR, and 94.8–105% with RSD of 1.1–6.6% for MEL. The proposed method has the characteristics of speed, sensitivity, and accuracy, and can be used for the routine determination of DCD, CYR, and MEL at the μg/kg level in complex animal tissue foods.

Development of Molecularly Imprinted Polymers for Solid Phase Extraction of Parabens in Plasma Samples and Analysis by UHPLC-MS/MS

Two molecularly imprinted polymers (MIPs) were synthesized, by sol-gel and radical polymerization procedures. These MIPs were evaluated as selective stationary phases for miniaturized solid phase extraction (MISPE) to determine parabens in plasma samples by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Selective cavities of the MIPs, based on molecular recognition (hydrogen bonds), were revealed after removal of the template (benzylparaben). Both MIPs were characterized by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR). MIP prepared by radical process presented higher selective binding capacity for the target parabens than MIP prepared by sol-gel. Several variables that influence MISPE performance, including sample pH, sorbent washing, elution solvent, and elution solvent volume were also evaluated. According to the analytical validation parameters, the MISPE/UHPLC-MS/MS method is suitable for the analysis of parabens in plasma samples. The effectiveness of this method was demonstrated through the analyses of the umbilical plasma samples from postpartum women.

Development of magnetic molecularly imprinted polymers for solid phase extraction of cocaine and metabolites in urine before high performance liquid chromatography – tandem mass spectrometry

A magnetic molecularly imprinted polymer (MMIP) has been synthesized and applied for cocaine (COC) and metabolites (benzoylecgonine, BZE; cocaethylene, CE; and ecgonine methyl ester, EME) recognition/pre-concentration in urine samples. The MMIP has been prepared using COC as a template molecule, ethylene dimethacrylate (EDMA) as a functional monomer, divinylbenzene (DVB) as a cross-linker, Fe3O4 magnetite as a magnetic component, and 2,2′-azobisisobutyronitrile (AIBN) as an initiator. The best results (MIP layer on the surface of the magnetic nanoparticles) and physical properties of the prepared MMIP were obtained when assisting the synthesis procedure with ultrasounds (325W, 37kHz, 30°C, 4h). After solid phase extraction (SPE) with the prepared adsorbent material, analytes were determined by high performance liquid chromatography – tandem mass spectrometry (HPLC–MS/MS). Variables affecting the SPE process (batch mode) were fully evaluated. Optimum retention of analytes (1.8mL of urine and 50mg of MMIP) was achieved by fixing the urine pH at 5.5 (use of a KH2PO4/NaOH, pH 5.5 buffer solution), and magnetic stirring (25°C, 700rpm) for 10min. Elution was performed by using 2mL of a dichloromethane/2-propanol/ammonium hydroxide (75:20:5) mixture under ultrasounds (325W, 35kHz, room temperature) for 5min. The method was validated according to the guidance for bioanalytical method validation of the US Department of Health and Human Services, Food and Drug Administration. The detection limits were in the range of 0.39–1.4ngL−1. The relative standard deviations of intra- and inter-day tests ranged from 5 to 11% and from 3 to 11%, respectively. Analytical recoveries were in the range of 79–106% when spiking drug-free urine samples at three concentration levels. Good results were also obtained after analyzing an FDT +25% control material. The applicability of the method was proved for screening/quantifying COC, BZE, CE and EME in several samples from poly-drug abusers.

Synthesis and Application of Glibenclamide Imprinted Polymer for Solid Phase Extraction in Serum Samples Using Itaconic Acid as Functional Monomer

Synthesis and Application of Glibenclamide Imprinted Polymer for Solid Phase Extraction in Serum Samples Using Itaconic Acid as Functional Monomer

Determination of Allura Red in Food by Ionic Liquid ß-Cyclodextrin-Cross-Linked Polymer Solid Phase Extraction and High-Performance Liquid Chromatography

ABSTRACTNovel solid phase extraction using an α-picoline ionic liquid-β-cyclodextrin-cross-linked polymer is reported with high-performance liquid chromatography for the determination of allura red. The linear dynamic range, limit of detection, limit of quantitation, and relative standard deviation values were 5.0–2.5 × 104 µg L−1, 0.35 µg L−1, 1.17 µg L−1, and 0.47%, respectively. The preconcentration factor of method was approximately fourteen, and the α-picoline based ionic liquid-β-cyclodextrin polymer may be used for up to thirteen times. The mechanism of adsorption was investigated by kinetic modeling and the inclusion interaction of the ionic liquid-β-cyclodextrin-cross-linked polymer with allura red was characterized. This method was employed for the determination of allura red in food with satisfactory results.

Simultaneous analysis of Alternaria toxins and citrinin in tomato: an optimised method using liquid chromatography-tandem mass spectrometry

Alternaria toxins and citrinin are mycotoxins produced by fungi growing on different raw materials and agricultural commodities. Maximum levels of these toxins in foods are currently under consideration by the European Commission as a risk management measure. In this study, a new quantitative method is described for the determination of five Alternaria toxins and citrinin in tomato and tomato juice samples based on LC-MS/MS detection. Samples were extracted with pure methanol, followed by a derivatisation step with 2,4-dinitrophenylhydrazine to improve the determination of tenuazonic acid and to decrease the wide polarity difference between the compounds of interest. Samples were purified on hydrophilic-modified styrene polymer solid-phase extraction cartridges. High-performance liquid chromatographic columns packed with different core–shell materials were tested for the separation of toxins and a C-18 phase was in the final method applied to achieve sufficient separation of all relevant analytes. A key element of this approach was to prove successful transferability of the method to three different triple quadrupole mass spectrometers. A full single laboratory method validation was performed on two LC-MS/MS systems and performance characteristics met the predefined requirements. Moreover, the method was used in an international proficiency test and the satisfactory z-scores obtained (−0.1 to 0.8 in tomato juice samples) demonstrated the reliability of the approach described. The method will be validated in an inter-laboratory collaborative study and if the criteria for method precision are met, the method will be proposed as a new Work Item to the European Committee for Standardisation.

Synthesis and application of cephalexin imprinted polymer for solid phase extraction in milk

Molecular imprinted polymer (MIP) against cephalexin was synthesized by co-polymerization of functional monomer, cross-linker, radical initiator, along with target molecule (cephalexin) in a porogenic material. Binding of cephalexin towards prepared MIP was studied in different solvents (water, methanol, 1M NaCl, acetone and acetonitrile) and best binding was observed in methanol. Partition coefficient and selectivity of prepared imprint and non-imprint was also studied. Cross reactivity in terms of binding efficiency was also assessed with other antibiotics. Chromatographic study of MIP was carried out by packing prepared imprint into glass column. MIP was used as matrix in solid phase extraction (SPE) for recovery of cephalexin from spiked milk samples for further estimation by high performance liquid chromatography. No interference was observed from milk components after elution of cephalexin from MIP, indicating selectivity and affinity of MIP. On the other hand, interference was observed in eluate obtained from C18 SPE column.

Preparation of 17β-estradiol-imprinted material by surface-initiated atom transfer radical polymerization and its application.

A novel 17β-estradiol molecularly imprinted polymer was grafted onto the surface of initiator-immobilized silica by surface-initiated atom transfer radical polymerization. The resulting molecularly imprinted polymer was characterized by elemental analysis and thermogravimetric analysis. The binding property of molecularly imprinted polymer for 17β-estradiol was also studied with both static and dynamic methods. The results showed that the molecularly imprinted polymer possessed excellent recognition capacity for 17β-estradiol (180.65 mg/g at 298 K), and also exhibited outstanding selectivity for 17β-estradiol over the other competitive compounds (such as testosterone and progesterone). Then, the determination of trace 17β-estradiol in beef samples was successfully developed by using molecularly imprinted polymer solid-phase extraction coupled with high-performance liquid chromatography. The limit of detection was 0.25 ng/mL, and the amount of 17β-estradiol in beef samples was detected at 2.83 ng/g. This work proposed a sensitive, rapid, reliable, and convenient approach for the determination of trace 17β-estradiol in complicated beef samples.

Ionic-Liquid-Loaded β-Cyclodextrin-Cross-Linked Polymer Solid-Phase Extraction for the Separation/Analysis of Linuron in Fruit and Vegetable Samples

A novel method for the separation/analysis of linuron in fruit and vegetable samples is described. The work is based on the utilization of ionic liquid ([C6min][PF6])-loaded β-cyclodextrin cross-linked polymer (IL-β-CDCP) for the effective adsorption of linuron coupled with ultraviolet spectrophotometry. The inclusion interaction of IL-β-CDCP with linuron is studied with FTIR and inclusion constants. Under optimum conditions, the preconcentration factor achieved for this method is approximately 10. Linear range, limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation are 0.08–15.00 μg/mL, 5.8 ng/mL, 17.5 ng/mL and 0.96 % (n = 3, c = 4.0 μg/mL), respectively. This technique is successfully applied for determination of linuron in real samples.

A novel 2-cyanobenzothiazole-based (18)F prosthetic group for conjugation to 1,2-aminothiol-bearing targeting vectors.

In a bid to find an efficient means to radiolabel biomolecules under mild conditions for PET imaging, a bifunctional (18)F prosthetic molecule has been developed. The compound, dubbed [(18)F]FPyPEGCBT, consists of a 2-substituted pyridine moiety for [(18)F]F(-) incorporation and a 2-cyanobenzothiazole moiety for coupling to terminal cysteine residues. The two functionalities are separated by a mini-PEG chain. [(18)F]FPyPEGCBT could be prepared from its corresponding 2-trimethylammonium triflate precursor (100 °C, 15 min, MeCN) in preparative yields of 11% ± 2 (decay corrected, n = 3) after HPLC purification. However, because the primary radiochemical impurity of the fluorination reaction will not interact with 1,2-aminothiol functionalities, the (18)F prosthetic could be prepared for bioconjugation reactions by way of partial purification on a molecularly imprinted polymer solid-phase extraction cartridge. [(18)F]FPyPEGCBT was used to (18)F-label a cyclo-(RGDfK) analogue which was modified with a terminal cysteine residue (TCEP·HCl, DIPEA, 30 min, 43 °C, DMF). Final decay-corrected yields of (18)F peptide were 7% ± 1 (n = 9) from end-of-bombardment. This novel integrin-imaging agent is currently being studied in murine models of cancer. We argue that [(18)F]FPyPEGCBT holds significant promise owing to its straightforward preparation, 'click'-like ease of use, and hydrophilic character. Indeed, the water-tolerant radio-bioconjugation protocol reported herein requires only one HPLC step for (18)F peptide purification and can be carried out remotely using a single automated synthesis unit over 124-132 min.

Molecularly Imprinted Solid-Phase Extraction: Extraction of Traditional Chinese Medicine Active Ingredients

Molecular imprinting technology (MIT) is a developing technique with high recognition which is just like the recognition between enzymes and antibodies in the organism. Molecularly imprinted polymers (MIPs), synthetic materials obtained using the imprinting technology, have played a huge advantage and been used in many fields. Especially, MIPs have been applied to the extraction and separation of analytes as the selective adsorbent of solid-phase extraction (SPE), which is known as molecularly imprinted polymer solid-phase extraction (MISPE) in recent years. In the present review, the methodology of MIPs preparation and evaluation are explained. Moreover, recent great developments of SPE and MISPE are discussed, and the potential application of MISPE in extraction of traditional Chinese medicine (TCM) active ingredients are also presented briefly.

Surface Plasmon Resonance‐based Inhibitive Immunoassay Coupled with Dummy Template Molecularly Imprinted Polymer Solid Phase Extraction for On‐line Analysis of Trace Clenbuterol

AbstractA new indirect inhibitive immunoassay using surface plasmon resonance (SPR) coupled with molecularly imprinted polymer (MIP) was developed and applied for the analysis of trace clenbuterol (CL). A MIP coating using phenylephrine as the dummy template was synthesized in a flexible quartz capillary (30 cm×0.25 mm i.d.) by in situ polymerization technique, which then was used as the online solid phase extraction (SPE) tube before SPR detection. The thickness of the coating was 198 nm on average, illustrated by scanning electron microscope (SEM) image. The mechanism for adsorption of CL on dummy template MIP was found to be a Freundlich isotherm and pseudo‐second‐order model. The immunoassay was conducted on BIAcore 3000 biosensor automatically without pre‐treatment. The calibration curve was generated by linear fit in the range of 0.1–10 ng L‐1 and 10–100 ng L‐1. The detection limit was 0.1 ng L–1, which is super sensitive. This method was directly applied for the analysis of real‐world samples without pretreatment.

Use of Modified Diethylamine Phosphorus-containing Polymer for Solid Phase Extraction of Cobalt and Lead in Fruit Samples Employing Flame Atomic Absorption Spectrometry

Use of Modified Diethylamine Phosphorus-containing Polymer for Solid Phase Extraction of Cobalt and Lead in Fruit Samples Employing Flame Atomic Absorption Spectrometry

Selective and simultaneous determination of NSAIDs in equine plasma by HPLC with molecularly imprinted solid-phase extraction.

Detection of nonsteroidal anti-inflammatory drugs (NSAIDs) in equine plasma is a significant analytical problem in veterinary anti-doping controls. A new HPLC method coupled to selective extraction with molecularly imprinted polymers was developed for the simultaneous determination in equine plasma of the NSAIDs phenylbutazone, flunixin, oxyphenbutazone, ketoprofen and naproxen. The analytical performances of the method have been evaluated both in standard solutions and equine plasma samples. Recovery: Molecularly imprinted polymers solid-phase extraction for all NSAIDs was >94% with intra-day values below 15.0% and inter-day values below 20%. Method quantification limit was 0.01 μg/ml. The developed method could be considered as a useful alternative to existing screening methods for the determination of NSAIDs in the context of studies of pharmacokinetics and anti-doping controls.

Molecularly imprinted polymers for solid phase extraction of orghanophosphorus pesticides

Molecularly imprinted polymer-solid phase extraction (MIP-SPE) adsorbent was prepared for the analysis of selected organophosphorus pesticides(OPPs) in environmental sample. In this work, the influence of process parameters on the preparation of imprinted polymer is presented. In theprocedure of polymerization, molecularly imprinted bulk polymer was prepared using quinalphos and methacrylic acid (MAA) as template molecule and functional monomer, respectively. The influence of the following parameters on recognition properties was investigated namely, types of crosslinker (ethylene glycol dimethacrylate (EGDMA) or divinylbenzene (DVB)) and porogenic solvents (acetonitrile, dichloromethane, toluene, chloroform). Molar ratio of template:functional monomer:cross linker was fixed at 1:4:20. Soxhlet extraction method was conducted to remove the imprint molecule in order to create the recognition sites. A blank/non-imprinted polymer (NIP) was produced simultaneously using identical procedure except in the absence of template molecule.

Molecularly Imprinted Polymer for Solid-Phase Extraction of Phenolic Acids from Salicornia herbacea L.

This paper reports the application of a molecularly imprinted polymer (MIP) for the extraction and separation of phenolic acids from Salicornia herbacea L. (S. herbacea) using a solid phase extraction (SPE) system. The template of the MIP for phenolic acid extraction and separation was selected experimentally as one of seven templates. The obtained material with Benzoic acid (BA) as a template had the best extraction capacity of phenolic acids from S. herbacea. Water and methanol/HCl were selected as a washing solvent and elution solvent, respectively. The good linearity was obtained for the three targets, ranging from 10 to 500 μg mL−1 (R2 > 0.999), with relative standard deviations ≤ 5.0%. Overall, the proposed method using MIPs is expected to have a wide range of applications.