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Development of molecular imprinted nanosensor for determination of tobramycin in pharmaceuticals and foods

In this study, we developed quartz crystal microbalance (QCM) nanosensor for the real-time detection of tobramycin (TOB). Firstly, the modification of gold surface of QCM chip was performed by self-assembling monolayer formation of allyl mercaptane to introduce polymerizable double bonds on the chip surface. Then, TOB imprinted poly(2-hydroxyethyl methacrylate-methacryloylamidoglutamic acid) [p(HEMA-MAGA)] film was generated on the gold surface. The nonmodified and TOB-imprinted p(HEMA-MAGA) surfaces were characterized by using atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, ellipsometry and contact angle measurements. The proposed method was validated according to the ICH guideline. The linearity range and the detection limit (S/N=3) were obtained as 1.7×10(-11)-1.5×10(-10) M and 5.7×10(-12) M, respectively. The developed method was applied to pharmaceuticals, and food samples such as chicken egg white and milk extract for the determination of TOB. In addition, association kinetics analysis and isotherm models were applied to the data to explain the adsorption process that took place.

Determination of omeprazole in pharmaceuticals by derivative spectroscopy

A new derivative UV spectroscopic method was developed for the analysis of omeprazole in borate buffer (pH 10.0; 0.1 M). Second derivative spectra were generated between 200-400 nm at N = 9, delta gamma = 31.5. The linearity range for values obtained from second derivative spectra was 0.2-40.0 micrograms ml-1. The developed method was applied to five different commercial preparations of hard gelatin capsules containing enteric coated granules. The relative standard deviations were found to be 2.24% (brand A), 1.87% (brand B), 2.80% (brand C), 4.55% (brand D) and 1.09% (brand E). The data were compared with ones obtained from the polarographic method given in the literature and no difference was found statistically.

Determination of Lansoprazole in pharmaceutical dosage forms by two different spectroscopic methods

Abstract Two different ultraviolet (UV) spectroscopic methods were developed for determination of Lansoprazole in pharmaceutical dosage forms. The solutions of the standard and the sample were prepared in 0.1 M NaOH and phosphate buffer pH 6.6. Both UV spectrophotometric and derivative spectroscopic techniques were applied. Second-order derivative spectra were generated between 200 and 400 nm at N=9, Δλ=31.5. The linear range for the UV spectrophotometric method was 3.0–25.0 μg ml−1 and that for the derivative spectroscopic method was 0.5–25.0 μg ml−1. The developed methods were applied to three different pharmaceutical preparations. The percentage recovery was 100.2%.

Simultaneous determination of rosiglitazone and metformin in plasma by gradient liquid chromatography with UV detection

A novel, fast and simple liquid chromatographic method was developed and validated for the simultaneous determination of rosiglitazone and metformin in human plasma. The analysis was performed on a phenyl column (250mmx4.6mm i.d., 5mum) using a gradient method starting with mobile phase composed of acetonitrile:5mM acetate buffer pH 5.5 (75:25, v/v). The flow rate was 1mLmin(-1). UV detection was performed at 245nm and verapamil was used as internal standard. The total run time was less than 10min. Sample preparation included a simple protein precipitation step with acetonitrile. Validation experiments were performed to demonstrate stability, specificity, sensitivity, linearity, accuracy, precision and robustness. The limit of quantification was 100ngmL(-1) for rosiglitazone and 250ngmL(-1) for metformin. The extraction recoveries were 100.02-105.0% for rosiglitazone and 105.64-103.88% for metformin. The method was applied with success to plasma samples obtained from diabetic patients undergoing treatment with rosiglitazone and metformin.

Determination of nifedipine in human plasma by square wave adsorptive stripping voltammetry

A simple, sensitive and selective square-wave adsorptive stripping voltammetric method has been developed and validated for the determination of nifedipine (NIF) in plasma. The assay was performed after single extraction of NIF from alkalinised plasma into organic phase. The adsorption behaviour of NIF on a hanging mercury drop electrode (HMDE) was explored by square-wave and cyclic voltammetry. The drug was accumulated at HMDE and a well-defined peak was obtained at -730 mV versus Ag/AgCl in borate buffer of pH 9.0 including 0.01 M KCl. The linear concentration range was 2.89 x 10(-9) M-3.61 x 10(-7) M (1.00-125.01 ng ml(-1)) when using 30 s accumulation time at -300 mV. Limit of detection and limit of quantification were 1.21 x 10(-9) M (0.42 ng ml(-1)) and 2.89 x 10(-9) M (1.00 ng ml(-1)) respectively. The intra-day relative standard deviation (RSD) ranged from 1.93 to 4.12% at three concentrations and the inter-day RSDs varied from 2.53 to 6.68%. The method was applied, to the plasma of pregnant women suffering from pregnancy induced hypertension, for the determination of NIF. The percentage recoveries varied from 96.26 to 99.49%. It has been shown that NIF could be determined in the presence of its main metabolite (dehydronifedipine) by the developed method.

Adsorptive stripping voltammetric methods for determination of ezetimibe in tablets

Abstract In this study, square-wave adsorptive stripping voltammetry (SWAdSV) and differential pulse adsorptive stripping voltammetry (DPAdSV) were used for determination of ezetimibe (EZE) in the presence of 0.1 m K2HPO4–Na2B4O7 (1:1) supporting electrolyte. The well-defined peaks for SWAdSV were observed at accumulation time of 15 s, accumulation potential of -0.80 V, frequency of 15 Hz, pulse amplitude of 25 mV, potential increment of 4 mV. For DPAdSV, accumulation time of 15 s, accumulation potential of -0.85 mV, scan rate of 20 mV/s and pulse amplitude of 50 mV were found as the best apparatus parameters. EZE gave rise to a single voltammetric peak in the potential interval from -1236 to -1252 mV for SWAdSV and interval from -1190 to -1210 mV for DPAdSV. The developed methods were validated according to the ICH guideline and were found to be linear, sensitive, specific, precise and accurate. The linearity ranges of EZE for SWAdSV and DPAdSV are 33–596 ng/ml and 66–400 ng/ml, respectively. The developed method was applied successfully for the determination of EZE in tablet dosage form.

Quantitative analysis of ezetimibe in human plasma by gas chromatography-mass spectrometry

A new, specific and sensitive GC-MS method with electron impact ionization technique was developed for quantitative analysis of ezetimibe (EZE) in human plasma. Prior to GC analysis, EZE was derivatized with N-methyl-N-trimethylsilyl-trifluoroacetamide (MSTFA), which is a trimethyl silylating reagent. The derivatization reaction was optimized and parameters such as catalyst, derivatization time, temperature, solvent and the volume of silylating reagent were investigated. Trimethylsilyl ether derivative of EZE was determined in selected ion monitoring (SIM, mass-to-charge ratio (m/z): 326) mode. The method was validated with respect to LOD and LOQ, precision, accuracy, linearity, specificity, stability, and recovery. The LOQ and LOD were found as 15 and 10 ng/mL, respectively. The linearity of the method ranged from 15 to 250 ng/mL. The correlation coefficient of the calibration curve was 0.9977 +/- 0.0004 (+/- S.E.M.). The intra- and inter-day precisions (RSD) were less than 6% and accuracies (bias) for intra- and inter-day accuracy were found between -4.04 and 9.71% at four different concentration levels (15, 40, 100, 250 ng/mL). The proposed method was successfully applied to real human plasma samples for determination of total EZE.

Simultaneous spectrophotometric determination of ezetimibe and simvastatin in pharmaceutical preparations using chemometric techniques

Two spectrophotometric methods are described for the simultaneous determination of ezetimibe (EZE) and simvastatin (SIM) in pharmaceutical preparations. The obtained data was evaluated by using two different chemometric techniques, Principal Component Regression (PCR) and Partial Least-Squares (PLS-1). In these techniques, the concentration data matrix was prepared by using the mixtures containing these drugs in methanol. The absorbance data matrix corresponding to the concentration data matrix was obtained by the measurements of absorbances in the range of 240 - 300 nm in the intervals with Δλ = 1 nm at 61 wavelengths in their zero order spectra, then, calibration or regression was obtained by using the absorbance data matrix and concentration data matrix for the prediction of the unknown concentrations of EZE and SIM in their mixture. The procedure did not require any separation step. The linear range was found to be 5 - 20 µg mL-1 for EZE and SIM in both methods. The accuracy and precision of the methods were assessed. These methods were successfully applied to a pharmaceutical preparation, tablet; and the results were compared with each other.

Application of Micellar Electrokinetic Capillary Chromatography for the Determination of Nifedipine and Its Degradation Product in Pharmaceutical Preparations

Abstract A simple and rapid micellar electrokinetic capillary chromatographic (MEKC) method for the analysis of nifedipine (NIF) and its degradation product was developed and validated. The compounds were separated using a 100 mM borate buffer at pH 9.0 containing 15 mM sodium dodecyl sulphate (SDS) and 25% acetonitrile, applied voltage of 30 kV, at working temperature 30°C and fused silica capillary of 72 cm effective length. Hydrodynamic injection (50 mbar) was applied for 3 s. The detection wavelength was set at 236 nm. Nimodipine was used as internal standard (IS) to compensate for minor fluctuations of migration times. Under the optimum conditions NIF, nitroso analog of dehydronifedipine (NDNIF) (degradation product exposed to sunlight) and IS were well separated with in 9 min. The method was validated with respect to linearity range, limit of detection and quantitation, precision, accuracy, specificity, ruggedness, and robustness. The method exhibited low limit of detection as 0.5 µg mL−1, wide linearity range of 2–100 µg mL−1 and high efficiency 1 × 105 N/m for NIF. The method was applied to the tablet form of NIF containing pharmaceutical preparations. The data were compared with that of the differential pulse polarographic method mentioned in literature. No significant difference was found statistically.