Application of response surface modeling optimization in UV spectrophotometric determination of 4-aminobenzoic acid by molecularly imprinted polypyrrole.

Selective determination of 4-aminobenzoic acid (ABA) in pharmaceutical and human serum samples was performed by molecularly imprinted polypyrrole and ultraviolet (UV) spectrophotometry, based on precipitation polymerization. The molecularly imprinted polymer (MIP) was prepared using pyrrole functional monomer and ABA template molecules. The significant factors controlling the performance of the synthesized ABAMIP sorbent were screened and optimized using Plackett- Burman design (PBD) and central composite design (CCD), respectively. The model was used to obtain the optimal values of the significant response factors. The predicted MIP to NIP response ratio demonstrated an approximate deviation of 5 % from the experimental value. Under the obtained optimal conditions, the calibration curve showed a linear range of 0.05-2 mM with a correlation coefficient (r2) of 0.9920 and a limit of detection (LOD) of 0.0310 mM. The method recovery for the analyte was obtained 88.10-100.5 in the investigated real samples. The proposed ABA-MIP sorbent showed an acceptable selectivity in the presence of some pharmaceuticals.

Application of gas flow headspace liquid phase micro extraction coupled with gas chromatography-mass spectrometry for determination of 4-methylimidazole in food samples employing experimental design optimization.

BACKGROUND: 4-Methylimidazole (4-MeI) or 4-methyl-1H-imidazole, a slightly yellowish solid with molecular formula C4H6N2, is a heterocyclic compound which supposedly does not exist as a natural product and is formed when carbohydrates are heating with ammonium compounds. This compound is used in pharmaceuticals, agriculture and photography chemicals, dyes and pigments, and rubber manufacturing. In the present study, a simple and efficient sample preparation method designated gas flow headspace liquid phase microextraction (GF-HS-SDME) was employed for the extraction and preconcentration of 4-methylimidazole (4-MeI) from food and beverage samples, before its determination by gas chromatography-mass spectrometry. RESULT: To investigate the optimal conditions for the extraction process in GF-HS-SDME method, factors affecting extraction, including selection of extraction solvent, vial volume, extraction solvent ratio, position of extracting solvent, drop volume, sample volume, stirring speed, temperature, extraction time, sample pH, ionic strength of the sample solution and gas flow rate were optimized by utilizing both one-variable-at-a-time method and Plackett-Burman design. The investigation of protocol was carried out by using a standard solution containing 100.0 µg L-1 of 4-MeI in deionized water. CONCLUSION: In this study, a simple and green analytical method based on GF-HS-SDME was proposed for the extraction and preconcentration of 4-MeI from foodstuffs, followed by GC-MS determination. The main advantage of this method is its high preconcentration factor and fastness due to the application of an inert gas stream during microextraction.

Selective determination of closantel by artificial neural network-genetic algorithm optimized molecularly imprinted polypyrrole using UV-visible spectrophotometry.

A molecularly imprinted polymer (MIP) for the selective solid-phase extraction (SPE) was prepared applying polymerization of pyrrole monomer in the presence of closantel (CLS) as a template molecule. The quantitative measurements were carried out using UV-Vis spectrophotometry. Several important parameters control the performance of polypyrrole sorbent. The influence of seven factors including loading time, polymerization time, amount of sorbent, stirring rate, desorption time, initiator concentration and monomer to template ratio were investigated. The optimization of parameters was performed using Plackett-Burman design (PBD), central composite design (CCD), artificial neural network (ANN) and genetic algorithm (GA). The Pareto plot showed that the effects of loading time, reaction time and amount of sorbent are most important to the process. These significant factors were investigated using CCD and the obtained data were used to train the ANN. The predicted model obtained from the trained ANN was introduced to GA as the fitness function to be optimized. The calibration curve demonstrated linearity over a concentration range of 0.010-10 mM with a correlation coefficient (R2) of 0.9833 under optimal condition. The synthesized MIP sorbent showed a good selectivity and sensitivity toward CLS. The limit of detection (LOD) for CLS was obtained 1.0 µM. The real sample analysis was performed to determine CLS in pharmaceutical and human serum samples.

A new molecularly imprinted polymer for selective extraction and pre-concentration of guaifenesin in different samples: Adsorption studies and kinetic modeling.

This paper describes the synthesis of a molecularly imprinted polymer by chemical oxidation of pyrrole as the functional monomer, and at the presence of guaifenesin as the template. The prepared polymer was used as adsorbent in molecularly imprinted solid-phase extraction followed by spectrophotometric determination. Different parameters in the solid-phase extraction including sample pH, adsorbent weight, washing solution, and elution solvent were studied to determine optimum conditions for isolation and enrichment of guaifenesin. The results showed guaifenesin was quantitatively adsorbed on the molecularly imprinted polymer at pH 6.0 and completely eluted with an ethanol-water solution (50% v/v). An enrichment factor of four with satisfactory recoveries (87.0-95.0%) was obtained. The solid-phase extraction columns could be used for up to six consecutive elution-loading cycles without significant decreases in the analyte recoveries. The method had a dynamic range of 3.0 × 10-6 -1.5 × 10-4  mol/L with a limit of detection and limit of quantification of 1.4×10-6 and 4.5×10-6  mol/L, respectively. The proposed procedure was used for the extraction and determination of guaifenesin in different pharmaceutical formulations, with satisfying results being achieved.

Nanogram/mL detection of nortriptyline: Preparation of a molecularly imprinted polymer for spectrophotometric determination of nortriptyline based on multivariate optimization methods.

In this work, the molecularly imprinted polymer was used as a selective sorbent in solid-phase extraction method for the spectrophotometric determination of nortriptyline at 239 nm. Molecularly imprinted polymer was synthesized by pyrrole as a functional monomer in the presence of nortriptyline as a template. Several factors, consist of the concentration of the monomer to template ratio, amount of initiator, stirring rate, reaction time, the pH of the buffer solution, amount of sorbent, loading time, shaking rate of loading, extraction time, and shaking rate of extraction were evaluated due to their effectiveness in the preparation and extraction capability of molecularly imprinted polymer. Multivariate optimization methods, such as Plackett-Burman and central composite designs, were employed to find and optimize the significant factors. Under the selected optimal conditions, molecularly imprinted polymer showed a linear range from 0.1 to 100 µmol/L (0.026 to 26 µg/mL) nortriptyline, a detection limit of 10.3 nmol/L (2.7 ng/mL), a highly repeatable (relative standard deviation of 3.7%) and reproducible response (relative standard deviation of 4.6%), and a good selectivity in the presence of structurally related molecules. Furthermore, molecularly imprinted polymer showed high extraction efficiency and was successfully used for the determination of nortriptyline in real samples.

Determination of methimazole based on electropolymerized-molecularly imprinted polypyrrole modified pencil graphite sensor.

Preparation of a molecularly imprinted polymer (MIP) film and its recognition property for methimazole (MMZ) was investigated. The polypyrrole (PPy) film was prepared by the cyclic voltammetric deposition of pyrrole in the presence of a supporting electrolyte (NaClO4·H2O) with and without MMZ through on a pencil graphite electrode (PGE). A computational study based on density functional theory was developed to evaluate the template-monomer geometry and interaction energy in the prepolymerization mixture. The performance of MIP sensor and non-imprinted polymer (NIP) film was evaluated by differential pulse voltammetry (DPV). The most important parameters controlling the performance of sensor were investigated and optimized. The prepared electrode was used for MMZ measurement by a three-step procedure, including analyte extraction in the electrode, electrode washing and electrochemical measurement of MMZ. The molecularly imprinted film exhibited a high selectivity and sensitivity toward methimazole in the experimental conditions. The calibration curve demonstrated linearity over a concentration range of 0.007-6mM with a correlation coefficient (r2) of 0.9808. The accuracy of the method was studied through spiking blank samples showed recovery of 98% with precision of 4%. Limit of detection based on S/N=3 was obtained 3×10-6M. The proposed sensor was applied successfully to determine MMZ in biological model samples and pharmaceuticals.

Spectrophotometric determination of fluoxetine by molecularly imprinted polypyrrole and optimization by experimental design, artificial neural network and genetic algorithm.

A selective method based on molecularly imprinted polymer (MIP) solid-phase extraction (SPE) using UV-Vis spectrophotometry as a detection technique was developed for the determination of fluoxetine (FLU) in pharmaceutical and human serum samples. The MIPs were synthesized using pyrrole as a functional monomer in the presence of FLU as a template molecule. The factors that affecting the preparation and extraction ability of MIP such as amount of sorbent, initiator concentration, the amount of monomer to template ratio, uptake shaking rate, uptake time, washing buffer pH, take shaking rate, Taking time and polymerization time were considered for optimization. First a Plackett-Burman design (PBD) consists of 12 randomized runs were applied to determine the influence of each factor. The other optimization processes were performed using central composite design (CCD), artificial neural network (ANN) and genetic algorithm (GA). At optimal condition the calibration curve showed linearity over a concentration range of 10-7-10-8M with a correlation coefficient (R2) of 0.9970. The limit of detection (LOD) for FLU was obtained 6.56×10-9M. The repeatability of the method was obtained 1.61%. The synthesized MIP sorbent showed a good selectivity and sensitivity toward FLU. The MIP/SPE method was used for the determination of FLU in pharmaceutical, serum and plasma samples, successfully.

Bioactive sesquiterpene lactone from Artemisia santolina / Lactona sesquiterpénica bioactiva de Artemisia santolina

Most species of genus Artemisia L. (Compositae) are medicinal herbswith several uses in the folk medicine worldwide. In the present study, methanol extract of Artemisia santolina has been subjected for isolation of its metabolites along with evaluation of cytotoxic activity against Artemia salina larvae. The structures of the compounds determined by 1H-and 13C-NMR, HMQC, HMBC, 1H-1H COSY and Mass spectral analysis. Two sesquiterpenes, 1,5-dihydroxy- 4(15)eudesman-12,6-olid (artemin) (1), 2-hidroxy-2,6,10-trimethyl-7,10- oxide-3,11-dodecadien-5-one (2) and one flavonoid, 5,7,4'-trihydroxy-6,3'-dimethoxyflavone (jaceosidin) (3) have been successfully characterized. Cytotoxicity of the sesquiterpene lactone (1), was assessed on Artemia salina larvae and resulted in IC50 value of 6.44 µg/mL, which was more potent compared to the positive standard berberine hydrochloride (IC50 = 26 µg/mL). In this study, the separation and identification of two sesquiterpenes and one flavone from the aerial parts of A. santolina is described. Among them the compound artemin (1) showed a toxicity effect against A. salina nauplii.

La mayoría de las especies del género Artemisia L. (Compositae) son hierbas medicinales con varios usos en la medicina popular en todo el mundo. En el presente estudio, el extracto metanólico de Artemisia santolina ha sido sometido al aislamiento de sus metabolitos junto con la evaluación de la actividad citotóxica contra las larvas de Artemia salina. Las estructuras de los compuestos se determinaron mediante RMN 1H y 13C, HMQC, HMBC, 1H-1H COZY y análisis espectral de masas. Dos sesquiterpenos, 1,5-dihidroxi-4 (15) eudesman- 12,6-olid (artemin) (1), 2-hidroxi-2,6,10-trimetil-7,10-óxido-3,11-dodecadien-5-ona (2) y un flavonoide, 5,7,4'-trihidroxi-6,3'- dimetoxiflavona (jaceosidina) (3). Se evaluó la citotoxicidad de la lactona sesquiterpénica (1) en larvas de Artemia salina y resultó en un valor de CI50 de 6,44 µg/ml, que era más potente en comparación con el clorhidrato de berberina estándar positivo (CI50 = 26 µg/ml). En este estudio se describe la separación e identificación de dos sesquiterpenos y una flavona de las partes aéreas de A. santolina. Entre ellos, el compuesto artemin (1) mostró un efecto de toxicidad contra los nauplios de A. salina.

An innovative method for analysis of Pb (II) in rice, milk and water samples based on TiO2 reinforced caprylic acid hollow fiber solid/liquid phase microextraction.

In the present study, nano-sized titanium oxides were applied for preconcentration and determination of Pb(II) in aqueous samples using hollow fiber based solid-liquid phase microextraction (HF-SLPME) combined with flame atomic absorption spectrometry (FAAS). In this work, the nanoparticles dispersed in caprylic acid as an extraction solvent was placed into a polypropylene porous hollow fiber segment supported by capillary forces and sonification. This membrane was in direct contact with solutions containing Pb (II). The effect of experimental conditions on the extraction, such as pH, stirring rate, sample volume, and extraction time were optimized. Under the optimal conditions, the performance of the proposed method was investigated for the determination of Pb (II) in food and water samples. The method was linear in the range of 0.6-3000µgmL-1. The relative standard deviations and relative recovery of Pb (II) was 4.9% and 99.3%, respectively (n=5).

Magnetically responsive polycaprolactone nanoparticles for progesterone screening in biological and environmental samples using gas chromatography.

A new Fe3O4/poly(є-caprolactone) (PCL) magnetite nanocomposite was fabricated and used as a sorbent for magnetically mediated PCL microspheres solid-phase extraction (MM-PCL-SPE) followed by gas chromatography-flame ionization detection (GC-FID) for monitoring of progesterone (PGN) hormone in biological and environmental matrices, namely blood serum, tap water, urine, and hospital wastewater. The nanomagnetite core of the sorbent was synthesized by a co-precipitation method. Magnetic nanoparticles (MNPs) were then microencapsulated with PCL microspheres using emulsion polymerization. The nanocomposite was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The magnetite sorbent can be effectively dispersed in aqueous solution and attracted to an external magnetic field. The MM-PCL-SPE process for PGN assay involved (a) dispersion of the sorbent in the donor phase aqueous solution with sonication, (b) exposure to a magnetic field to collect sorbent that had adsorbed the analyte, and (c) solvent desorption of extracted PGN for GC-FID analysis. The work demonstrates the usefulness of MM-PCL-SPE in the rapid and sensitive monitoring of trace amounts of PGN in real samples. The limit of detection (LOD) and limit of quantification (LOQ) were 1.00 and 3.30 ng/mL, respectively. The relative recoveries in real samples were adequate. Linearity was observed over a wide range of 2.2-10,000.0 ng/mL in aqueous media and urine and 0.01-70.0 µg/mL in blood serum. Graphical Abstract In this research new Fe3O4/poly(є-caprolactone) (PCL) magnetite microspheres were developed as an efficient sorbent for solid-phase extraction of progesterone hormone in biological and environmental matrices.

Computational design and multivariate optimization of an electrochemical metoprolol sensor based on molecular imprinting in combination with carbon nanotubes.

This work describes the development of an electrochemical sensor based on a new molecularly imprinted polymer for detection of metoprolol (MTP) at ultra-trace level. The polypyrrole (PPy) was electrochemically synthesized on the tip of a pencil graphite electrode (PGE) which modified whit functionalized multi-walled carbon nanotubes (MWCNTs). The fabrication process of the sensor was characterized by cyclic voltammetry (CV) and the measurement process was carried out by differential pulse voltammetry (DPV). A computational approach was used to screening functional monomers and polymerization solvent for rational design of molecularly imprinted polymer (MIP). Based on computational results, pyrrole and water were selected as functional monomer and polymerization solvent, respectively. Several significant parameters controlling the performance of the MIP sensor were examined and optimized using multivariate optimization methods such as Plackett-Burman design (PBD) and central composite design (CCD). Under the selected optimal conditions, MIP sensor was showed a linear range from 0.06 to 490 µmol L(-1) MTP, a limit of detection of 2.88 nmol L(-1), a highly reproducible response (RSD 3.9%) and a good selectivity in the presence of structurally related molecules. Furthermore, the applicability of the method was successfully tested with determination of MTP in real samples (tablet, and serum).

1,4-dihydroxyanthraquinone electrochemical sensor based on molecularly imprinted polymer using multi-walled carbon nanotubes and multivariate optimization method.

The present work describes development of a simple and cost-effective electrochemical sensor for determination of 1,4-dihydroxyanthraquinone (1,4-DAQ) based on molecularly imprinted polypyrrole (PPY). The molecularly imprinted polymer (MIP) was electrochemically synthesized onto surface of multi-walled carbon-nanotubes-modified pencil graphite electrode (MWCNs-PGE). A computational approach was employed to select the best functional monomer for rational design of MIP. Based on the computational results, pyrrole (PY) was selected as functional monomer. Plackett-Burman design (PBD) was used for selecting the variables which affected the analytical response (current). After screening, the main factors that affect on the MIP-MWCNTs-PGE response efficiency were also optimized using central composite design (CCD). Under the optimized conditions, calibration curve of the imprinted sensor showed a linear concentration range from 10 nmol L(-1) to 100 µmol L(-1), with the limit of detection (LOD) of 4.15 nmol L(-1). The imprinted sensor showed the advantages of high porous surface structure, ease of preparation, good reproducibility and repeatability, high selectivity and sensitivity. Furthermore, the proposed method was successfully extended for the determination of 1,4-DAQ in serum and plasma real samples.

Electrochemical preparation of a molecularly imprinted polypyrrole modified pencil graphite electrode for the determination of phenothiazine in model and real biological samples.

A sensitive electrochemical sensor for determination of phenothiazine (PTZ) was introduced based on molecularly imprinted polymer (MIP) film. A computational study was performed to evaluate the template-monomer geometry and interaction energy in the prepolymerization mixture. The electrode was prepared during electropolymerization of pyrrole (Py) on a pencil graphite electrode (PGE) by cyclic voltammetry (CV) technique. The quantitative measurements were performed using differential pulse voltammetry (DPV) in Britton-Robinson (BR) buffer solutions using 60% (v/v) acetonitrile-water (ACN/H2O) binary solvent. The effect of important parameters like pH, monomer concentration, number of cycles, etc on the efficiency of MIP electrode was optimized and the calibration curve was plotted at optimal conditions. Two dynamic linear ranges of 1-300 µmol L(-1) and 0.5-10 mmol L(-1) were observed. The detection limit (based on S/N=3) of PTZ was obtained 3×10(-7) mol L(-1). The MIP/PGE has been successfully applied as a selective sensor for fast and accurate determination of PTZ in some model and real biological samples.