Determination of dicofol in aquatic products using molecularly imprinted solid-phase extraction coupled with GC-ECD detection

The novel molecularly imprinted microsphere (MIM) that could be applied as special sorbent was synthesized by aqueous suspension polymerization using 1,1-bis(4-chlorophenyl)-1,2,2,2-tetrachloroethane (α-chloro-DDT) as the dummy template. The obtained MIM exhibited good recognition and selectivity to dicofol and it was successfully applied as selective sorbent of solid-phase extraction for the determination of dicofol from aquatic products. At the optimum conditions of the molecularly imprinted solid-phase extraction (MISPE) coupled with GC-ECD, good linearity for dicofol was achieved in a range of 0.4-100 ng g⁻¹ (r² = 0.9995) and the recoveries at three spiked levels were ranged from 85.8% to 101.2% for aquatic products with the relative standard deviation (RSD) less than 5.6%. The presented MISPE-GC-ECD method exhibited the advantages of simplicity, selectivity and sensitivity, and could be potentially applied to the determination of dicofol in complicated aquatic products.     

Sampling 4-chlorophenol in water by DGT technique with molecularly imprinted polymer as binding agent and nylon membrane as diffusive layer

For the first time, a diffusive gradients in thin films (DGT) device using molecularly imprinted polymer (MIP) as the binding agent and nylon membrane (NM) as the diffusive layer (NM-MIP-DGT) has been developed for sampling 4-chlorophenol (4-CP) in water. The MIP was prepared by precipitation polymerization with methacrylic acid as monomer and ethyleneglycoldimethacrylate as cross-linker. The diffusion coefficient of 4-CP through NM was obtained to be 0.788 ± 0.040 μ cm² s⁻¹ by diffusion cell method. The ratio was 1.01 ± 0.05 (mean ± standard deviation) for the concentration of 4-CP sampled by NM-MIP-DGT and analyzed by HPLC method to the total concentration of 4-CP in the synthetic solution where free 4-CP species dominated. The results showed that NM-MIP-DGT could sample 4-CP in synthetic solution accurately. The performance of NM-MIP-DGT for sampling 4-CP was independent of pH in the range of 3–7 and ionic strength in the range of 0.0001–0.1 mol L⁻¹ NaCl solution. The concentration of free form of 4-CP sampled by NM-MIP-DGT decreased with the increasing concentration of dissolved organic carbon in different water samples due to the electrostatic interaction of natural organic compounds with 4-CP. 1.8 mg L⁻¹ of the free form of 4-CP was determined by HPLC which was sampled by NM-MIP-DGT in an intermediate untreated industrial effluent. The NM-MIP-DGT can be a potential passive tool for sampling the free form of 4-CP in water.     

Molecularly imprinted solid-phase extraction for the selective determination of bromhexine in human serum and urine with high performance liquid chromatography

In this work, a novel method is described for the determination of bromhexine in biological fluids using molecularly imprinted solid-phase extraction as the sample cleanup 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 bromhexine as the template molecule. The novel imprinted polymer was used as a solid-phase extraction sorbent for the extraction of bromhexine from human serum and urine. Various parameters affecting the extraction efficiency of the polymer have been evaluated. The optimal conditions for molecularly imprinted solid-phase extraction (MISPE) consisted of conditioning 1 mL methanol and 1 mL of deionized water at neutral pH, loading of 5 mL of the water sample (25 μg L⁻¹) at pH 6.0, washing using 2 mL acetonitrile/acetone (1/4, v/v) and elution with 3× 1 mL methanol/acetic acid (10/1, v/v). The MIP selectivity was evaluated by checking several substances with similar molecular structures to that of bromhexine. Results from the HPLC analyses showed that the calibration curve of bromhexine using MIP from human serum and urine is linear in the ranges of 0.5-100 and 1.5-100 μg L⁻¹ with good precisions (3.3% and 2.8% for 5.0 μg L⁻¹), respectively. The recoveries for serum and urine samples were higher than 92%.     

Determination of trace bisphenol A in complex samples using selective molecularly imprinted solid-phase extraction coupled with capillary electrophoresis

The highly selective, fast and effective sample pretreatment technique molecularly imprinted solid-phase extraction (MISPE) can overcome the low sensitivity of the highly efficient capillary electrophoresis-UV method (CE-UV). In this work, narrowly dispersible bisphenol A (BPA)-imprinted polymeric microspheres with a high capacity factor of k′ = 6.8 and an imprinted factor of I = 6.53 were investigated as selective solid-phase extraction (SPE) sorbents for use in extraction of BPA from different sample matrices (tap water, wastewater, Yangtze River water, soil from the Yangtze River, shrimp and human urine). Washing and eluting protocols of MISPE were optimized. Under optimal conditions, recoveries of MISPE were investigated. Recoveries were basically constant and the relative standard deviation (RSD) was lower than 5.8% when loading volumes changed from 1 to 50 mL. Recoveries ranged from 71.20% to 86.23% for different sample matrices. Compared with C18 SPE, MISPE had higher selectivity and recovery for BPA. BPA was determined with good accuracy and precision in different complex samples using CE-UV coupled with MISPE. Spiked recoveries ranged from 95.20% to 105.40%, and the RSD was less than 7.2%. Because a large loading volume was achieved, the enrichment efficiency of pretreatment and the sensitivity of this method were improved. The limits of detection of this MISPE-CE-UV method for BPA in tap water, wastewater, Yangtze River water, soil from the Yangtze River, shrimp and human urine were 3.0 μg L^− 1, 5.4 μg L^− 1, 6.9 μg L^− 1, 2.1 μg L^− 1, 1.8 μg L^− 1 and 84 μg L^− 1, respectively.     

Development of a group selective molecularly imprinted polymers based solid phase extraction of malachite green from fish water and fish feed samples

A group selective molecularly imprinted solid phase extraction (MISPE) for malachite green (MG) from fish water and fish feed samples was developed. Using MG as template molecule, methacrylic acid as functional monomer, ethylene glycoldimethacrylate as linking agent and bulk polymerization as synthetic method, the molecularly imprinted polymers (MIPs) were synthesized and characterized with rebinding experiment. The Scatchard polt's analysis revealed that the template-polymer system showed the two-site binding behavior with dissociation constants of 0.3194 μmol L⁻¹ and 15.70 μmol L⁻¹, respectively. MG and two structurally related compounds, leucomalachite green (LMG) and crystal violet (CV) were employed for selectivity test. The MIPs exhibited the highest selective rebinding to MG, but also displayed 83.0% and 87.5% of cross-reactivity with LMG and CV, demonstrating that MIPs could be used as group recognition sorbents in solid phase extraction. The extraction conditions of MISPE column for MG were optimized. Tap water samples spiked with MG at concentration of 0.5-10 ng mL⁻¹ were extracted by MISPE column and analyzed by high performance liquid chromatography. The recoveries of MISPE column for MG extraction were found to be 76.8-93.7% with the relative standard deviations of 2.12-10.09%, indicating the feasibility of the prepared MIPs for MG extraction. No detectable MG was observed in one fish farming water sample and two fish feed samples; while the MG concentrations in two pet fishpond water samples were found at 1.50 ng mL⁻¹ and 0.67 ng mL⁻¹, respectively.     

Use of a bisphenol-A imprinted polymer as a selective sorbent for the determination of phenols and phenoxyacids in honey by liquid chromatography with diode array and tandem mass spectrometric detection

An extraction-preconcentration procedure based on the use of a molecularly imprinted polymer (MIP) as selective sorbent has been developed for the determination of several phenolic compounds (bisphenol-A, bisphenol-F and 4-nitrophenol) and phenoxyacid herbicides (2,4-D, 2,4,5-T and 2,4,5-TP) in honey samples. Liquid chromatography with diode array detection (LC-DAD) and electrospray ionisation-ion trap mass spectrometry (LC-IT-MS) were used for the separation, identification and quantification of these analytes.The molecularly imprinted polymer was obtained by precipitation polymerisation with bisphenol-A (BPA) as template and 4-vinylpyridine as the functional monomer. The behaviour of this sorbent was compared with those of other materials frequently used in SPE. The selectivity of the BPA-MIP for the target analytes was tested in samples containing other pesticides in common use. The recoveries achieved for all six compounds were in the 81-96% range.By applying the proposed procedure prior to LC-IT-MS, the limits of detection achieved in commercial honey samples were in the 0.1-3.8 ng g⁻¹ range, with relative standard deviations of 12-24%.     

A new strategy for synthesis of an in-tube molecularly imprinted polymer-solid phase microextraction device: Selective off-line extraction of 4-nitrophenol as an example of priority pollutants from environmental water samples

In this study a novel preparation protocol has been developed for the construction of an in-tube molecularly imprinted polymer-solid phase microextraction (MIP-SPME) device. Open tubular capillaries have been molded from a polymer sorbent imprinted for 4-nitrophenol as target molecule. Different parameters like inner diameter and volume of the polymer, porogen volume, swelling and shrinking effects of the polymer tubes, polymerization time, pH of the sample, extraction time, ‘salting out’ effect and serial connection of the tubes were evaluated and optimized. Particularly, an optimized polymer preparation process and extraction condition enhanced the final extraction recovery of 4-nitrophenol substantially. Using this new MIP-SPME technique with high-performance liquid chromatography-ultraviolet (HPLC-UV) analysis of the extracts, the linear range and the limits of detection and quantification are 0.001–10 mg L⁻¹, 0.33 μg L⁻¹ and 1.1 μg L⁻¹ respectively. At optimized conditions, a mixture of nitrophenols, alkylated and chlorinated phenols spiked into municipal waste water were analyzed to evaluate the matrix effects and cross selectivity of the new MIP capillary tubes.     

Molecularly imprinted nano particles combined with miniaturized homogenous liquid–liquid extraction for the selective extraction of loratadine in plasma and urine samples followed by high performance liquid chromatography-photo diode array detection

In this work a molecularly imprinted polymer was developed as a selective sorbent for extraction of loratadine (as a model) in complex matrices followed by miniaturized homogeneous liquid–liquid extraction (MHLLE) for the first time. The molecularly imprinted polymer (MIP) which is based on loratadine as the template was synthesized successfully by precipitation polymerization and was used as a selective sorbent. This technique was applied for preconcentration, sample preparation, and determination of loratadine using high performance liquid chromatography-photo diode array detection (HPLC-PDA). Optimization of various parameters affecting molecular imprinted solid phase extraction (MISPE), such as pH of adsorption, composition and volume of eluent, adsorption and desorption times were investigated. Besides, in the subsequent stage (MHLLE) the type and volume of extraction solvent, sodium hydroxide amount, surfactant concentration, and extraction time were investigated and optimized. Under the optimal condition, maximum enrichment capacity and Langmuir constant were 91 mg g⁻¹ and 0.014 L mg⁻¹, respectively. Furthermore, enrichment factor and extraction recovery of MIP-MHLLE method were 30 and 90%, respectively. The LOD of the proposed method was 0.2 μg L⁻¹ and a linear dynamic range of 1–1000 μg L⁻¹ was obtained with correlation coefficient of greater than 0.998. The present method was applied for extraction and determination of loratadine in plasma and urine samples in μg L⁻¹ levels and satisfactory results were achieved (RSD <8% based on three replicate measurements).     

Molecularly imprinted solid-phase extraction for the selective determination of 17β-estradiol in fishery samples with high performance liquid chromatography

A molecularly imprinted polymer (MIP) has been synthesized by a thermo-polymerization method using methacrylic acid (MAA) as functional monomer, ethylene glycol dimethacrylate (EGDMA) as cross-linker, acetonitrile as porogenic solvent, and 17β-estradiol as template. The MIP showed obvious affinity for 17β-estradiol in acetonitrile solution, which was confirmed by absorption experiments. After optimization of molecularly imprinted solid-phase extraction (MISPE) conditions, three structurally related estrogenic compounds (17β-estradiol, estriol, and diethylstilbestrol) were used to evaluate the selectivity of the MIP cartridges. The MIP cartridges exhibited highly selectivity for E₂, the recoveries were 84.8 ± 6.53% for MIPs and 19.1 ± 1.93% for non-imprinted polymer (NIP) cartridges. The detection and quantification limits correspond to 0.023 and 0.076 mg L⁻¹. Furthermore, the MISPE methods were used to selectively extract E₂ from fish and prawn tissue prior to HPLC analysis. This MISPE-HPLC procedure could eliminate all matrix interference simultaneously and had good recoveries (78.3-84.5%).     

Synthesis and characterization of a novel molecularly imprinted polymer for simultaneous extraction and determination of water-soluble and fat-soluble synthetic colorants in chilli products by solid phase extraction and high performance liquid chromatography

A sorbent was synthesized and investigated for molecularly imprinted solid phase extraction (MISPE). Molecularly imprinted polymers (MIP) were synthesized via precipitation polymerization procedure, where 4-vinyl pyridine (4-VP) was used as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The imprinting effect of the MISPE was evaluated by elution experiments. The resulting MISPE showed high extraction selectivity to water-soluble and fat-soluble synthetic colorants. The determination of multi-residue for three kinds of water-soluble and six kinds of fat-soluble synthetic colorants in chilli products was also investigated by HPLC coupled with MISPE. The mean recoveries calculated by solvent calibration curve for water-soluble and fat-soluble synthetic colorants were from 72.1% to 95.6% for chilli spice and 72.1% to 92.3% for chilli powder. The decision limit (CCα) and the detection capability (CCβ) obtained for water-soluble and fat-soluble synthetic colorants were in the range of 1.2–1.6 and 1.9–2.4 μg kg⁻¹ in chilli spice and chilli powder. The resulting MISPE was successfully used off-line for the determination of nine kinds of synthetic colorants in chilli products.     

Molecularly imprinted polymer for the extraction of parabens from environmental solid samples prior to their determination by high performance liquid chromatography-ultraviolet detection

An analytical methodology incorporating a molecularly imprinted solid-phase extraction procedure (MISPE) has been developed for the determination of parabens in environmental solid samples. Four different polymers were prepared combining the use of acetonitrile or toluene as porogen, and 4-vinylpyridine (VP) or methacrylic acid (MAA) as monomer, using benzylparaben (BzP) as a template molecule. Although all the polymers were able to recognize the template in rebinding experiments, the MIP prepared in toluene using MAA showed better performance. This polymer was also capable of recognizing other parabens (methyl, ethyl, isopropyl, propyl, isobutyl, butyl and benzylparaben) allowing to develop an appropriated MISPE procedure for this family of compounds. The extraction of the parabens from environmental solid samples was performed by ultrasonic assisted extraction in small columns (SAESC), and this procedure next to MISPE as clean-up step followed by HPLC-UV determination was successfully used for the determination of parabens in soil and sediment samples of different locations. Recoveries ranging from 80% to 90% have been achieved depending on the compound and the samples, and limits of detection (LODs) were under 1 ng g⁻¹ for all the compounds, making this method suitable for the determination of parabens in environmental solid matrices. The method was further applied to the determination of paraben contents in real samples, founding levels up to 11.5 ng g⁻¹ in sea sediments.     

A 3,3′-dichlorobenzidine-imprinted polymer gel surface plasmon resonance sensor based on template-responsive shrinkage

Molecularly imprinted polymer gel film on the gold substrate of a chip was prepared with minute amount of cross-linker for the fabrication of a surface plasmon resonance (SPR) sensor sensitive to 3,3′-dichlorobenzidine. The molecularly imprinted gel film was anchored on a gold chip by a surface-bound photo-radical initiator. The sensing of 3,3′-dichlorobenzidine is based on responsive shrinkage of the imprinted polymer gel film that is triggered by target binding. This change can improve the responsiveness of the imprinted SPR sensor to 3,3′-dichlorobenzidine. The molecularly imprinted polymer gel film was characterized with contact angle measurements, electrochemical impedance spectroscopy, cyclic voltammogram, swelling measurements and atomic force microscopy. The changes of SPR spectroscopy wavenumber shifts revealed that the imprinted gel sensing film can ‘memorize’ the binding of 3,3′-dichlorobenzidine compared to non-imprinted one. The imprinted gel-SPR sensor showed a linear response in the range of 9.0 × 10⁻¹² to 5.0 × 10⁻¹⁰ mol L⁻¹ (R² = 0.9998) for the detection of 3,3′-dichlorobenzidine, and it also exhibited high selectivity to 3,3′-dichlorobenzidine compared to its structurally related analogues. We calculated the detection limits to be 0.471 ng L⁻¹ for tap water and 0.772 ng kg⁻¹ for soil based on a signal to noise ratio of 3. The method showed good recoveries and precision for the samples spiked with 3,3′-dichlorobenzidine. This suggest that the imprinted gel-SPR sensing method can be used as a promising alternative for the detection of 3,3′-dichlorobenzidine.     

An optical sensor for the determination of digoxin in serum samples based on a molecularly imprinted polymer membrane

This paper reports the synthesis and testing of a molecularly imprinted polymer membrane for digoxin analysis. Digoxin-specific bulk polymer was obtained by the UV initiated co-polymerisation of methacrylic acid and ethylene glycol dimethacrylate in acetonitrile as porogen. After extracting the template analyte, the ground polymer particles were mixed with plasticizer polyvinyl chloride to form a MIP membrane. A reference polymer membrane was prepared from the same mixture of monomers but with no template. The resultant membrane morphologies were examined by scanning electron microscopy. The imprinted membrane was tested as the recognition element in a digoxin-sensitive fluorescence sensor; sensor response was measured using standard solutions of digoxin at concentrations of up to 4 × 10⁻³ mg L⁻¹. The detection limit was 3.17 × 10⁻⁵ mg L⁻¹. Within- and between-day relative standard deviations RSD (n = 5) were in the range 4.5-5.5% and 5.5-6.5% respectively for 0 and 1 × 10⁻³ mg L⁻¹ digoxin concentrations. A selectivity study showed that compounds of similar structure to digoxin did not significantly interfere with detection for interferent concentrations at 10, 30 and 100 times higher than the digoxin concentration. This simply manufactured MIP membrane showed good recognition characteristics, a high affinity for digoxin, and provided satisfactory results in analyses of this analyte in human serum.     

A novel molecularly imprinted polymer for simultaneous extraction and determination of sudan dyes by on-line solid phase extraction and high performance liquid chromatography

A novel molecularly imprinted polymer was synthesized with attapulgite employed as matrix, which is simple and time-saving. In this method, sudan I was chosen as template molecule, 2-vinylpyridine as functional monomer and ethylene glycol dimethacrylate as cross-linking agent, respectively. The imprinted polymer was characterized by the infrared spectroscopy and transmission electron microscopy. Then the selectivity experiments were performed on sudan dyes and the recognition coefficients for sudan I, sudan II, sudan III and sudan IV were 2.9, 1.9, 1.9 and 2.3, respectively. As the packing material of solid-phase extraction, the imprinted polymer has been applied to on-line concentration of the four sudan dyes in samples from Yellow River water, tomato sauce and sausage. The corresponding analytical methods to determine these sudan dyes have been developed. The limits of detection for these sudan dyes were in the range of 0.01–0.05 ng mL⁻¹ for Yellow River water, 1.0–3.0 ng g⁻¹ for tomato sauce and 0.8–3.0 ng g⁻¹ for sausage.     

Determination of multi-residue for malachite green,gentian violet and their metabolites in aquatic products by high-performance liquid chromatography coupled with molecularly imprinted solid-phase extraction

A sorbent was synthesized and investigated for molecularly imprinted solid-phase extraction (MISPE). Molecularly imprinted polymers (MIPs) were synthesized via precipitation polymerization procedure, where methacrylic acid (MAA) was used as functional monomer and ethylene glycol dimethacrylate (EDMA) as cross-linking agent. The imprinting effect and selectivity of the MISPE were evaluated by elution experiments. The resulting MISPE showed high extraction selectivity to malachite green, gentian violet and their metabolites, which may be caused by both the ion exchange and the hydrophobic interactions. The determination of multi-residue for malachite green, gentian violet and their metabolites in aquatic products by HPLC coupled with MISPE was also investigated. The mean recoveries calculated by solvent calibration curve for malachite green (MG), gentian violet (GV), leucomalachite green (LMG) and leucogentian violet (LGV) were from 89.8% to 99.1% for grass carp, 90.6% to 101.2% for shrimp and 91.3% to 96.3% for shellfish. The decision limit (CCα) and the detection capability (CCβ) obtained for MG, GV, LMG and LGV were in the range of 0.11–0.14 and 0.19–0.24 μg kg⁻¹ for grass carp, shrimp and shellfish. The MISPE was successfully used off-line for the determination of MG, GV and their metabolites in aquatic products.     

Synthesis by precipitation polymerisation of molecularly imprinted polymer microspheres for the selective extraction of carbamazepine and oxcarbazepine from human urine

Two molecularly imprinted polymers (MIPs), in the physical form of well-defined polymer microspheres, were synthesised via precipitation polymerisation (PP) using an antiepileptic drug, carbamazepine (CBZ), as template molecule, methacrylic acid as functional monomer and either divinylbenzene 80 (DVB-80) or a mixture of DVB-80 and ethylene glycol dimethacrylate (EGDMA) as crosslinking agents. The MIP obtained using DVB-80 alone as crosslinking agent (MIP A) had a narrow particle size distribution (9.5 ± 0.5 μm) and a well-developed permanent pore structure (specific surface area in the dry state = 758 m² g⁻¹), whereas when a mixture of DVB-80 and EGDMA (MIP B) were used as crosslinking agents, the polymer obtained had a broader particle size distribution (6.4 ± 1.8 μm) and a relatively low specific surface area (23 m² g⁻¹). The molecular recognition character of both polymers was evaluated by means of LC and then a molecularly imprinted solid-phase extraction (MISPE) protocol; CBZ was recognised by both polymers, and useful cross-selectivity for oxcarbazepine (OCBZ), which is the main metabolite of CBZ, also observed. In a detailed bioanalytical study, MIP A was selected in preference to MIP B since MIP A enabled a high volume of sample to be extracted such that lower limits of detection were achievable using this polymer. High recoveries of CBZ and OCBZ were obtained in a MISPE protocol when 50 mL of human urine spiked at 0.2 mg L⁻¹ were percolated through MIP A (90% and 83%, respectively).     

Molecularly imprinted polymer coated magnetite nanoparticles as an efficient mefenamic acid resonance light scattering nanosensor

In this work, a mefenamic acid (MFA) nanosensor was synthesized by the aid of molecularly imprinted polymer (MIP) technique. MIP layer was coated on magnetite nanoparticles as magnetic nano-carriers. Synthesized nanoparticles were characterized using various measurements techniques. Light scattering properties of the synthesized nanoparticles in the presence or absence of MFA have been selected as the detection signal. In this regard, resonance light scattering has been used as the detection method. Various factors that can potentially affect light scattering efficiency (i.e., pH, ultrasonication time and nanoparticle dosage) were optimized using “one-at-a-time” method. A linear dynamic range was established from 100.0 to 2000.0 ng L⁻¹ of MFA and the limit of detection was found to be 50.0 ng L⁻¹ using the proposed method.     

Amperometric determination of chloroguaiacol at submicromolar levels after on-line preconcentration with molecularly imprinted polymers

In this study, a sorbent flow preconcentration system coupled to amperometric detector for the chloroguaiacol (4-chloro-2-methoxyphenol) determination at submicromolar levels is described. The satisfactory selectivity of the proposed method was attained by means of the use of a chloroguaiacol-imprinted polymer, whose the synthesis was carried out by bulk polymerization. Flow and chemical parameters associated to the preconcentration system, such as sample pH, preconcentration and elution flow rates, concentration of the carrier solution (KCl) and eluent volume were investigated through multivariate analysis. The flow preconcentration of chloroguaiacol was not affect by equimolar presence of structurally similar phenolic compounds including catechol, 4-chloro-3-methylphenol, 4-aminophenol and 2-cresol, thus showing the good performance of the imprinted polymer. Under the best experimental conditions, it was obtained a preconcentration factor of 110-fold and low detection and quantification limits of 27 and 78 nmol L⁻¹, respectively. The analytical curve covered a wide linear range from 0.05 up to 5.0 μmol L⁻¹ (r > 0.999) and satisfactory precision (n = 8) evaluated by relative standard deviation (R.S.D.) were respectively, 5.5 and 4.2%, for solutions of 1.0 and 5.0 μmol L⁻¹ chloroguaiacol. Other parameters related to the performance of the flow system were also evaluated including concentration efficiency of 27.5 min⁻¹ and consumptive index of 0.09 mL. Recoveries varying from 93 up to 112% for water samples (tap water and river water) spiked with chloroguaiacol concentration were achieved, thus assuring the accuracy of the proposed flow preconcentration system.     

Solid-phase molecularly imprinted pre-concentration and spectrophotometric determination of isoxicam in pharmaceuticals and human serum

A selective molecularly imprinted polymer (MIP) has been synthesized for isoxicam pre-concentration, followed by its spectrophotometric determination based on hydrogen bonding interactions between examined drug and alizarin yellow GG. This method is able to evaluate isoxicam in range of 1.0 × 10⁻³ to 20.0 μg mL⁻¹, with a limit of determination of 1.0 ng mL⁻¹. The retention capacity and pre-concentration factor of prepared sorbent are 18.5 mg g⁻¹ and 200, respectively; and the prepared MIPs can be reused at least for five times. The MIP capability for isoxicam selection and extraction from the solution is higher than non-imprinted polymer (NIP). Under optimum conditions, this procedure can be successfully applied to assay trace amounts of isoxicam in pharmaceutical and biological samples.     

Selective solid-phase extraction of dibutyl phthalate from soybean milk using molecular imprinted polymers

An analysis method is reported for dibutyl phthalate and related compounds with high selectivity and sensitivity by using the selective molecularly imprinted solid-phase extraction (MISPE) technique. In this report, dibutyl phthalate (DBP) is employed as the template molecule, and the molecularly imprinted polymers (MIPs) are synthesized through the bulk polymerization of methacrylic acid (MAA). The Scatchard plot suggests that the template-polymer system has two-site binding behavior with the dissociation constants of 0.5187 and 0.01898 mmol L⁻¹, respectively. The rebinding test, based on the MISPE column technique, shows the recoveries of soybean milk samples spiked with 5 phthalates are in the range of 75.8-107.5% with the relative standard deviations of 1.80-10.08%, indicating the feasibility of the prepared MIPs for phthalates extraction. Finally, the method is used to analyze the trace level of phthalates in commercial soybean milk.