A micellar electrokinetic chromatography method for the determination of sumatriptan succinate in pharmaceutical formulations was developed. The effects of several factors such as pH, surfactant and buffer concentration, applied voltage, capillary temperature, and injection time were investigated. Separation took about 5 min using phenobarbital as internal standard. The separation was carried out in reversed polarity mode at 20 °C, 26 kV and using hydrodynamic injection for 10s. Separation was achieved using a bare fused-silica capillary 50 μm×40 cm and background electrolyte of 25 mM sodium dihydrogen phosphate-adjusted with concentrated phosphoric acid to pH 2.2, containing 125 mM sodium dodecyl sulfate and detection was at 226 nm. The method was validated with respect to linearity, limits of detection and quantification, accuracy, precision and selectivity. The calibration curve was linear over the range of 100-2000 μg mL(-1). The relative standard deviations of intra-day and inter-day precision for migration time, peak area, corrected peak area, ratio of corrected peak area and ratio of peak area were less than 0.68, 3.48, 3.28, 2.97 and 2.83% and 2.01, 5.50, 4.46, 4.92 and 4.07%, respectively. The proposed method was successfully applied to the determinations of the analyte in tablet. Forced degradation studies were conducted by introducing a sample of sumatriptan succinate standard solution to different forced degradation conditions using neutral (water), basic (0.1 M NaOH), acidic (0.1 M HCl), oxidative (10% H(2)O(2)) and photolytic (exposure to UV light at 254 nm for 2 h). It is concluded that the stability-indicating method for sumatriptan succinate can be used for the analysis of the drug in various samples.
A three-phase hollow fiber liquid-phase microextraction method coupled with CE was developed and used for the determination of partition coefficients and analysis of selected nitrophenols in water samples. The selected nitrophenols were extracted from 14 mL of aqueous solution (donor solution) with the pH adjusted to pH 3 into an organic phase (1-octanol) immobilized in the pores of the hollow fiber and finally backextracted into 40.0 microL of the acceptor phase (NaOH) at pH 12.0 located inside the lumen of the hollow fiber. The extractions were carried out under the following optimum conditions: donor solution, 0.05 M H(3)PO(4), pH 3.0; organic solvent, 1-octanol; acceptor solution, 40 microL of 0.1 M NaOH, pH 12.0; agitation rate, 1050 rpm; extraction time, 15 min. Under optimized conditions, the calibration curves for the analytes were linear in the range of 0.05-0.30 mg/L with r(2)>0.9900 and LODs were in the range of 0.01-0.04 mg/L with RSDs of 1.25-2.32%. Excellent enrichment factors of up to 398-folds were obtained. It was found that the partition coefficient (K(a/d)) values were high for 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,6-dinitrophenol and that the individual partition coefficients (K(org/d) and K(a/org)) promoted efficient simultaneous extraction from the donor through the organic phase and further into the acceptor phase. The developed method was successfully applied for the analysis of water samples.
A simple, rapid and validated capillary electrophoretic method has been developed for the separation and determination of ofloxacin and ornidazole in pharmaceutical formulations with detection at 230 nm. Optimal conditions for the quantitative separations were investigated. Analysis times shorter than 4 min were obtained using a background electrolyte solution consisting of 25 mmol/L phosphoric acid adjusted with 1 M Tris buffer to pH 8.5, with hydrodynamic injection of 5 s and 20 kV separation voltage. The validation criteria for accuracy, precision, linearity and limits of detection and quantitation were examined and discussed. An excellent linearity was obtained in concentration range 25-250 microg/mL. The detection limits for ofloxacin and ornidazole were 1.03 +/- 0.11 and 1.80 +/- 0.06 microg/mL, respectively. The proposed method has been applied for the analysis of ofloxacin and ornidazole both individually and in a combined dosage tablet formulation. The proposed validated method showed recoveries between 96.16 and 105.23% of the nominal contents.
A micellar electrokinetic chromatography (MEKC) method for the simultaneous determination of the antiviral drugs acyclovir and valacyclovir and their major impurity, guanine, was developed. The influences of several factors (surfactant and buffer concentration, pH, applied voltage, capillary temperature and injection time) were studied. Using tyramine hydrochloride as internal standard, the analytes were all separated in about 4 min. The separation was carried out in reversed polarity mode at 28 degrees C, 25 kV and using hydrodynamic injection (15 s). The separation was effected in a fused-silica capillary 100 microm x 56 cm and a background electrolyte of 20 mM citric acid-1 M Tris solution (pH 2.75), containing 125 mM sodium dodecyl sulphate and detection at 254 nm. The method was validated with respect to linearity, limit of detection and quantification, accuracy, precision and selectivity. Calibration curves were linear over the range 0.1-1 microg/mL (guanine) and from 0.1 to 120 microg/mL for both valacyclovir and acyclovir. The relative standard deviations of intra- and inter-day migration times and corrected peak areas were less than 5.0%. The proposed method was successfully applied to the determination of the analytes in tablets and creams. From the previous study it is concluded that the stability-indicating method developed for acyclovir and valacyclovir can be used for analysis of the drug in various stability samples.
An efficient method for the simultaneous enantioseparation of cyproconazole, bromuconazole, and diniconazole enantiomers was developed by CD-modified MEKC using a dual mixture of neutral CDs as chiral selector. Three neutral CDs namely hydroxypropyl-beta-CD, hydroxypropyl-gamma-CD, and gamma-CD were tested as chiral selectors at different concentrations ranging from 10, 20, 30 and 40 mM, but enantiomers of the studied fungicides were not completely separated. The best dual chiral recognition mode for the simultaneous separation of cyproconazole, bromuconazole, and diniconazole enantiomers was achieved with a mixture of 27 mM hydroxypropyl-beta-CD and 3 mM hydroxypropyl-gamma-CD in 25 mM phosphate buffer (pH 3.0) containing 40 mM SDS to which methanol-acetonitrile (10%:5% v/v) was added as organic modifiers. The best separation was based on the appearance of 10 peaks simultaneously, with good resolution (R(s) 1.1-15.9), and peak efficiency (N>200,000). Good repeatabilities in the migration time, peak area, and peak height were obtained in terms of RSD ranging from (0.72 to 1.06)%, (0.39 to 3.49)%, and (1.90 to 4.84)%, respectively.
Seven flavonoid compounds have been isolated from the aerial parts of tiger's betel (Piper porphyrophyllum), which were identified as 5,7-dimethoxyflavone, 4',5,7-trimethoxy-flavone, 3',4',5,7-tetramethoxyflavone, 4'-hydroxy-3',5,7-trimethoxyflavone, 5-hydroxy-3',4',7-trimethoxyflavone, 4',5-dihydroxy-3',7-dimethoxyflavone and 5-hydroxy-7-methoxyflavanone. The identification of all compounds was achieved by physical properties and spectroscopically. These data were also confirmed by comparison with previously reported spectral data. Flavonoid compounds with high content in P. porphyrophyllum can probably be used as a chemical marker for this Piper species.
A liquid-phase microextraction coupled with LC method has been developed for the determination of organophosphorus pesticides (methidation, quinalphos and profenofos) in drinking water samples. In this method, a small amount (3 microL) of isooctane as the acceptor phase was introduced continually to fill-up the channel of a 1.5 cm polypropylene hollow fiber using a microsyringe while the hollow fiber was immersed in an aqueous donor solution. A portion of the acceptor phase (ca. 0.4 microL) was first introduced into the hollow fiber and additional amounts (ca. 0.2 microL) of the acceptor phase were introduced to replenish at intervals of 3 min until set end of extraction (40 min). After extraction, the acceptor phase was withdrawn and transferred into a 2 mL vial for a drying step prior to injection into a LC system. Parameters that affect the extraction efficiency were studied including the organic solvent, length of fiber, volume of acceptor and donor phase, stirring rate, extraction time, and effect of salting out. The proposed method provided good enrichment factors of up to 189.50, with RSD ranging from 0.10 to 0.29%, analyte recoveries of over 79.80% and good linearity ranging from 10.0 to 1.25 mg/L. The LOD ranged from 2.86 to 82.66 microg/L. This method was applied successfully to the determination of organophosphorus pesticides in selected drinking water samples.
A capillary electrophoretic (CE) method for the baseline separation of the enantiomers of primaquine diphosphate (PQ) and quinocide (QC) (a major contaminant) in pharmaceutical formulations is proposed. Both components were separated under the following conditions: 50 mm tris phosphate buffer (pH 3.0) containing 15 mm hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD) as background electrolyte; applied voltage, 16 kV; capillary temperature, 25 degrees C; detection wavelength, 254 nm; hydrostatic injection, 10 s. The separations were conducted using a 35 cm length and 50 microm i.d. uncoated fused silica capillary column. Under the optimized conditions, the components were successfully separated in about 5 min. Intraday precision of migration time and corrected peak areas when expressed as relative standard deviation ranged from 0.17 to 0.45 and 2.60 to 3.94%, respectively, while the interday precision ranged from 2.59 to 4.20 and 3.15 to 4.21%, respectively. After the validation exercise, the proposed method was applied for the determination of QC impurity in PQ formulations.
A capillary zone electrophoretic method has been developed and validated for the determination of the impurity quinocide (QC) in the antimalarial drug primaquine (PQ). Different buffer additives such as native cyclodextrins and crown ethers were evaluated. Promising results were obtained when either beta-cyclodextrin (beta-CD) or 18-crown-6 ether (18C6) were used. Their separation conditions such as type of buffer and its pH, buffer additive concentration, applied voltage capillary temperature and injection time were optimized. The use of 18C6 offers slight advantages over beta-CD such as faster elution times and improved resolution. Nevertheless, migration times of less than 5 min and resolution factors (R(s)) in the range of 2-4 were obtained when both additives were used. The method was validated with respect to selectivity, linearity, limits of detection and quantitation, analytical precision (intra- and inter-day variability) and repeatability. Concentrations of 2.12 and 2.71% (w/w) of QC were found in pharmaceutical preparations of PQ from two different manufacturers. A possible mechanism for the successful separation of the isomers is also discussed.
This review tracks a decade of dynamic kinetic resolution developments with a biocatalytic inclination using enzymatic/microbial means for the resolution part followed by the racemization reactions either by means of enzymatic or chemocatalyst. These fast developments are due to the ability of the biocatalysts to significantly reduce the number of synthetic steps which are common for conventional synthesis. Future developments in novel reactions and products of dynamic kinetic resolutions should consider factors that are needed to be extracted at the early synthetic stage to avoid inhibition at scale-up stage have been highlighted.
A new mesoporous silica based on the sol-gel material cyanopropyltriethoxysilane (CNPrTEOS) was successfully synthesized by the hydrolysis and condensation of CNPrTEOS in the presence of ammonium solution as catalyst and methanol as solvent. It was used as a solid-phase extraction sorbent for the simultaneous extraction of three organophosphorus pesticides, namely, polar dicrotophos and non-polar diazinon and chlorpyrifos. Analysis was performed using high-performance liquid chromatography with UV detection. CNPrTEOS was characterized by FTIR spectroscopy, field-emission scanning electron microscopy and nitrogen gas adsorption. The surface area and average pore diameter of the optimum sol-gel CNPrTEOS are 379 m(2) /g and 4.7 nm (mesoporous), respectively. The proposed solid-phase extraction based on CNPrTEOS exhibited good linearity in the range of 0.8-100 μg/L, satisfactory precision (1.15-3.82%), high enrichment factor (800) and low limit of detection (0.072-0.091 μg/L). The limits of detection obtained using the proposed solid-phase extraction method are well below the maximum residue limit set by European Union and are also lower (13.6-48.5×) than that obtained by using a commercial CN-SPE cartridge (0.98-4.41 μg/L). The new mesoporous sol-gel CNPrTEOS showed promising alternative as SPE sorbent material for the simultaneous extraction of polar and non-polar organophosphorus pesticides.
Recently, a simple, rapid, high-efficiency, selective, and sensitive method for isolation, preconcentration, and enrichment of analytes has been developed. This new method of sample handling is based on ferum oxides as magnetic nanoparticles (MNPs) and has been used for magnetic solid-phase extraction (MSPE) of various analytes from various matrices. This review focuses on the applications of modified ferum oxides, especially modified Fe3O4 MNPs, as MSPE adsorbent for pesticide isolation from various matrices. Further perspectives on MSPE based on modified Fe3O4 for inorganic metal ions, organic compounds, and biological species from water samples are also presented. Ferum(III) oxide MNPs (Fe2O3) are also highlighted.
In view of several disadvantages as well as adverse effects associated with the use of chemical processes for producing esters, alternative techniques such as the utilization of enzymes on multi-walled carbon nanotubes (MWCNTs), have been suggested. In this study, the oxidative MWCNTs prepared using a mixture of HNO3 and H2SO4 (1:3 v/v) were used as a supportive material for the immobilization of Candida rugosa lipase (CRL) through physical adsorption process. The resulting CRL-MWCNTs biocatalysts were utilized for synthesizing geranyl propionate, an important ester for flavoring agent as well as in fragrances. Enzymatic esterification of geraniol with propionic acid was carried out using heptane as a solvent and the efficiency of CRL-MWCNTs as a biocatalyst was compared with the free CRL, considering the incubation time, temperature, molar ratio of acid:alcohol, presence of desiccant as well as its reusability. It was found that the CRL-MWCNTs resulted in a 2-fold improvement in the percentage of conversion of geranyl propionate when compared with the free CRL, demonstrating the highest yield of geranyl propionate at 6h at 55°C, molar ratio acid: alcohol of 1:5 and with the presence of 1.0g desiccant. It was evident that the CRL-MWCNTs biocatalyst could be reused for up to 6 times before a 50% reduction in catalytic efficiency was observed. Hence, it appears that the facile physical adsorption of CRL onto F-MWCNTs has improved the activity and stability of CRL as well as served as an alternative method for the synthesis of geranyl propionate.
An alternative environmentally benign support was prepared from chitosan-chitin nanowhiskers (CS/CNWs) for covalent immobilization of Rhizomucor miehei lipase (RML) to increase the operational stability and recyclability of RML in synthesizing eugenyl benzoate. The CS/CNWs support and RML-CS/CNWs were characterized using X-ray diffraction, fluorescent microscopy, and Fourier transform infrared spectroscopy. Efficiency of the RML-CS/CNWs was compared to the free RML to synthesize eugenyl benzoate for parameters: reaction temperature, stirring rate, reusability, and thermal stability. Under optimal experimental conditions (50°C, 250 rpm, catalyst loading 3 mg/mL), a twofold increase in yield of eugenyl benzoate was observed for RML-CS/CNWs as compared to free RML, with the former achieving maximum yield of the ester at 62.1% after 5 hr. Results demonstrated that the strategy adopted to prepare RML-CS/CNWs was useful, producing an improved and prospectively greener biocatalyst that supported a sustainable process to prepare eugenyl benzoate. Moreover, RML-CS/CNWs are biodegradable and perform esterification reactions under ambient conditions as compared to the less eco-friendly conventional acid catalyst. This research provides a facile and promising approach for improving activity of RML in which the resultant RML-CS/CNWs demonstrated good operational stability for up to eight successive esterification cycles to synthesize eugenyl benzoate.
In this study, caged calcium alginate-caged multiwalled carbon nanotubes dispersive microsolid phase extraction was described for the first time for the extraction of polycyclic aromatic hydrocarbons (PAHs) from water samples prior to gas chromatographic analysis. Fluorene, phenanthrene and fluoranthene were selected as model compounds. The caged calcium alginate-caged multiwalled carbon nanotubes was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and thermal gravimetry analyses. The effective parameters namely desorption solvent, solvent volume, extraction time, desorption time, the mass of adsorbent and sample volume were optimized. Under the optimum extraction conditions, the developed method showed good linearity in the range of 0.5-50 ng mL-1 (R2 ≥ 0.996), low limits of detection and quantification (0.42-0.22 ng mL-1) (0.73-1.38 ng mL-1) respectively, good relative recoveries (71.2-104.2%) and reproducibility (RSD 1.8-12.4%, n = 3) for the studied PAHs in water sample. With high enrichment factor (1,000), short extraction time (<30 min), low amounts of adsorbent (100 mg) and low amounts of solvent (0.1 mol) have proven that the microsolid phase extraction method based on calcium alginate-caged multiwalled carbon nanotubes are environmentally friendly and convenient extraction method to use as an alternative adsorbent in the simultaneous preconcentration of PAHs from environmental water samples.
Despite organophosphorus pesticides (OPPs) benefits in controlling vector-borne diseases and noxious insects, the bioaccumulation and persistence in the soil system may metamorphose into new substances which could pose a serious threat to the ecosystems and human health. The generally low levels of OPPs residues and often the complexity of the soil matrix are the issues that researcher must deal with. Thus, it is essential to isolate and preconcentrate the OPPs from the matrix to reduce interference effects to obtain a reliable detection. Researchers have reported sample preparation techniques as a promising approach to improve analytical measurement of merits including recovery, precision, linearity, limit of detection, and limit of quantification. Under the selected conditions, limits of detection range between 0.001 and 143 ng/mL, and extraction recovery range between 5 and 154% were obtained. This review evaluates the challenges and opportunities, emphasizes the prospects of sampling techniques and various (micro)extraction coupled with chromatographic methods in different soil samples. Based on the finding, the extraction efficiency depended largely on the interaction between OPPs and extraction media. The fate, migration, toxicity impact, sampling procedure, and storage which influenced the sample preparation were comprehensively discussed.