Showing papers on "NQS published in 2009"
TL;DR: The proposed spectrophotometric method was successfully applied to the determination of FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47+/-0.96%.
35 citations
TL;DR: New simple and sensitive spectrophotometric and fluorimetric methods have been developed and validated for the determination of fluoxetine hydrochloride (FLX) in its pharmaceutical formulations and both methods were successfully applied.
Abstract: New simple and sensitive spectrophotometric and fluorimetric methods have been developed and validated for the determination of fluoxetine hydrochloride (FLX) in its pharmaceutical formulations. The spectrophotometric method was based on the reaction of FLX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium (pH 11) to form an orange-colored product that was measured at 490 nm. The fluorimetric method was based on the reaction of FLX with 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) in an alkaline medium (pH 8) to form a highly fluorescent product that was measured at 545 nm after excitation at 490 nm. The variables affecting the reactions of FLX with both NQS and NBD-Cl were carefully studied and optimized. The kinetics of the reactions were investigated, and the reaction mechanisms were presented. Under the optimum reaction conditions, good linear relationships were found between the readings and the concentrations of FLX in the ranges of 0.3-6 and 0.035-0.5 mug mL(-1) for the spectrophotometric and fluorimetric methods, respectively. The limits of detection were 0.1 and 0.01 mug mL(-1) for the spectrophotometric and fluorimetric methods, respectively. Both methods were successfully applied to the determination of FLX in its pharmaceutical formulations.
25 citations
TL;DR: The proposed method based on nucleophilic substitution reaction of PRX with 1,2-naphthoquinone-4-sulphonate in an alkaline medium to form an orange-colored product of maximum absorption peak (λ max) at 488 nm was developed and validated.
Abstract: Simple and rapid spectrophotometric method has been developed and validated for the determination of paroxetine (PRX) in tablets. The proposed method was based on nucleophilic substitution reaction of PRX with 1,2-naphthoquinone-4-sulphonate (NQS) in an alkaline medium to form an orange-colored product of maximum absorption peak (λmax) at 488 nm. The stoichiometry and kinetics of the reaction were studied, and the reaction mechanism was postulated. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with PRX concentration (C) was obeyed in the range of 1–8 μg mL−1. The regression equation for the calibration data was: A = 0.0031 + 0.1609 C, with good correlation coefficients (0.9992). The molar absorptivity (e) was 5.9 × 105 L mol−1 1 cm−1. The limits of detection and quantitation were 0.3 and 0.8 μg mL−1, respectively. The precision of the method was satisfactory; the values of relative standard deviations did not exceed 2%. The proposed method was successfully applied to the determination of PRX in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 97.17 ± 1.06 %. The results obtained by the proposed method were comparable with those obtained by the official method.
15 citations
TL;DR: A novel and simple spectrophotometric method based on the fact that tiopronin can catalyze the reaction between sodium 1,2-naphthoquinone-4-sulfonate and hydroxyl ion to form 2-hydroxy-1,4-nafonone in a buffer solution of pH 13.00 has been established and successfully applied to the determination of tiopronsin in pharmaceutical samples.
Abstract: A novel and simple spectrophotometric method for the determination of tiopronin with sodium 1,2-naphthoquinone-4-sulfonate (NQS) is established in this paper. The detailed mechanism is proposed and discussed. It is based on the fact that tiopronin can catalyze the reaction between sodium 1,2-naphthoquinone-4-sulfonate and hydroxyl ion to form 2-hydroxy-1,4-naphthoquinone in a buffer solution of pH 13.00 at the maximal absorption wavelength of 445 nm. When tetradecyl benzyl dimethyl ammonium chloride (Zeph) is added to the solution, the sensitivity of the reaction is improved. Beer's law is obeyed in a range of 0.39 - 15.67 microg mL(-1). The equation of linear regression is A = 0.11749 + 0.05914C (microg mL(-1)), with a linear correlation coefficient of 0.9973. The detection limit is 0.2 microg mL(-1), RSD is 0.88% and the recovery rate is in the range of 96.6 - 103.9%. Furthermore, the method has been validated and successfully applied to the determination of tiopronin in pharmaceutical samples.
7 citations
TL;DR: The results suggest that a proper scrutiny should be conducted before deciding the sort of quinone to be applied in denitrifying processes, and the heterogeneous effects observed also advise to consider both the respiratory rates and the yields as important parameters for deciphering the impact of RM on denitRifying processes.
3 citations
01 Jun 2009
TL;DR: In this article, a physics-based model for the non-quasi-static (NQS) effects occurring in heterojunction bipolar transistors (HBTs) is presented.
Abstract: A physics based model for the non-quasi-static (NQS) effects occurring in heterojunction bipolar transistors (HBTs) is presented. Following classical transistor theory, partitioned charge based (PCB) approach is extended to additionally model small-signal frequency-dependent (trans-) conductances. A new large-signal model is implemented in Verilog-A, and is tested for small-signal behavior. Results are compared with numerical device simulation, and its improvement is checked against the results obtained from PCB approach and widely used 2nd order LCR sub-circuit.
2 citations
Journal Article•
TL;DR: In this paper, two spectrophotometric methods were developed for the estimation of bicalutamide in both; bulk drug samples and formulations, based on the oxidative coupling of the drug with the reagent namely 3-methyl-2- benzothiazolinone hydrazone hydrochloride (MBTH, Method A) and ferric chloride solution.
Abstract: Two new simple, sensitive and cost effective visible spectrophotometric methods were developed for the estimation of bicalutamide in both; bulk drug samples and formulations. The first method was based on the oxidative coupling of the drug with the reagent namely 3-methyl-2- benzothiazolinone hydrazone hydrochloride (MBTH, Method A) and ferric chloride solution. Second method was based on reaction of 1, 2 – naphthoquinone - 4 - sulphonic acid (NQS, Method B). The absorbance of the chromogens was measured at their respective absorption maxima at 630 nm for MBTH and 453 nm for NQS against the corresponding reagent blank. The methods obeyed Beer’s law between 10-60 ;g/mL for MBTH and 2.5-25 ;g/mL for NQS. The results of the recovery experiments indicated that average recovery was above 99.83%. The interference studies also revealed the common excipients and other additives usually present in pharmaceutical dosage forms did not interfere in the proposed methods. The proposed methods are precise, accurate, sensitive and cost effective and can be used in routine analysis in quality control laboratories.
1 citations
TL;DR: It is verified that frequency-tuning range and oscillation amplitude can be overestimated by over 20% and more than a factor 2, respectively, without inclusion of the NQS effect in MOS-varactor models.
Abstract: Frequency dependent properties of accumulation-mode MOS varactors, which are key elements in many RF circuits, are dominated by Non-Quasi-Static (NQS) effects in the carrier transport. The circuit performances containing MOS varactors can hardly be reproduced without considering the NQS effect in MOS-varactor models. For the LC-VCO circuit as an example it is verified that frequency-tuning range and oscillation amplitude can be overestimated by over 20% and more than a factor 2, respectively, without inclusion of the NQS effect.