Simple Spectrophotometric Method for Determination of Paroxetine in Tablets Using 1,2-Naphthoquinone-4-Sulphonate as a Chromogenic Reagent

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 (ε) 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

New Spectrophotometric and Fluorimetric Methods for Determination of Fluoxetine in Pharmaceutical Formulations

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 μg mL−1 for the spectrophotometric and fluorimetric methods, respectively. The limits of detection were 0.1 and 0.01 μg mL−1 for the spectrophotometric and fluorimetric methods, respectively. Both methods were successfully applied to the determination of FLX in its pharmaceutical formulations

Stereoselective HPLC assay of donepezil enantiomers with UV detection and its application to pharmacokinetics in rats

Abstract This investigation describes a new precise, sensitive and accurate stereoselective HPLC method for the simultaneous determination of donepezil enantiomers in tablets and plasma with enough sensitivity to follow its pharmacokinetics in rats up to 12 h after single oral dosing. Enantiomeric resolution was achieved on a cellulose tris (3,5-dimethylphenyl carbamate) column known as Chiralcel OD, with UV detection at 268 nm, and the mobile phase consisted of n-hexane, isopropanol and triethylamine (87:12.9:0.1). Using the chromatographic conditions described, donepezil enantiomers were well resolved with mean retention times of 12.8 and 16.3 min, respectively. Linear response (r > 0.994) was observed over the range of 0.05-2 g/ml of donepezil enantiomers, with detection limit of 20 ng/ml. The mean relative standard deviation (R.S.D.%) of the results of within-day precision and accuracy of the drug were ≤10%. There was no significant difference (p > 0.05) between inter-and intra-day studies for each enantiomers which confirmed the reproducibility of the assay method. The mean extraction efficiency was 92.6-93.2% of the enantiomers. The proposed method was found to be suitable and accurate for the quantitative determination of donepezil enantiomers in tablets. The assay method also shows good specificity to donepezil enantiomers, and it could be successfully applied to its pharmacokinetic studies and to therapeutic drug monitoring

High Performance Liquid Chromatoqraphic Method for the Simultaneous Determination of Labetalol and Hydrochlorothiazide in Tablets and Spiked Human Plasma

A reversed-phase HPLC method with spectrophotometric detection was developed for the simultaneous determination of labetalol (LBT) and hydrochloro-thiazide (HCD). The chromatographic separation was performed using a Microbondapak C18 column (4.6 i.d. x 250 nm) and paracetamol as internal standard. A mobile phase consisting of 0.05 M phosphate buffer/acetonitrile of pH 4 (7:3) at a flow rate of 0.7 ml/min was used. The detection was affected spectrophotornetrically at 302 nm. The working concentration range was 0.3–10 µg/ml with detection limits of 0.05 µg/ml for both drugs. The lower quantitation limit was 0.25 µg/ml in the two cases. The method was successfully applied to tablets, the % recoveries were 99.45 ± 0.68 for LBT and 99.79 ± 0.75 for HCD. The method was extended to the in-vitro determination in spiked human plasma. The % recoveries were 91.12 ± 0.33 for LBT and 91.37 ± 0.40 for HCD. The interday and intraday precision and accuracy were evaluated in plasma by calculating the % RSD (n=5) and the % error and were found to be in the ranges of 1.18–4.1% and 0.38–0.36% for both drugs, respectively

Spectrophotometric study for the reaction between fluvoxamine and 1,2-naphthoquinone-4-sulphonate: Kinetic, mechanism and use for determination of fluvoxamine in its dosage forms.

Spectrophotometric study was carried out, for the first time, to investigate the reaction between the antidepressant fluvoxamine (FXM) and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 9), an orange-colored product exhibiting maximum absorption peak (lambda(max)) at 470nm was produced. The kinetics of the reaction was investigated and its activation energy was found to be 2.65kcalmol(-1). Because of this low activation energy, the reaction proceeded easily. The stoichiometry of the reaction was determined and the reaction mechanism was postulated. This color-developing reaction was successfully employed in the development of simple and rapid spectrophotometric method for determination of FXM in its pharmaceutical dosage forms. Under the optimized reaction conditions, Beer's law correlating the absorbance (A) with FXM concentration (C) was obeyed in the range of 0.6-8mugml(-1). The regression equation for the calibration data was A=0.0086+0.1348C, with good correlation coefficient (0.9996). The molar absorptivity (varepsilon) was 5.9x10(4)lmol(-1)cm(-1). The limits of detection and quantification were 0.2 and 0.6mugml(-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 FXM in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.47+/-0.96%. The results obtained by the proposed method were comparable with those obtained by the official method. The proposed method is superior to all the previously reported spectrophotometric methods for determination of FXM in terms of its simplicity and sensitivity. The method is practical and valuable for its routine application in quality control laboratories for analysis of FXM

Évaluation et Production de Plongements de Mots à Partir de Contenus Web Français à Grande Échelle

International audienceDistributed word representations are popularly used in many tasks in natural language processing, adding that pre-trained word vectors on huge text corpus achieved high performance in many different NLP tasks. This paper introduces multiple high-quality word vectors for the French language where two of them are trained on massive crawled French data and the others are trained on an already existing French corpus used to pretrain FlauBERT model. We also evaluate the quality of our proposed word vectors and the existing French word vectors on the French word analogy task. In addition, we do the evaluation on multiple NLU tasks that shows the important performance enhancement of the pre-trained word vectors during this study compaed to the existing and random ones. Finally, we created a demo web application to test and visualize the obtained word embeddings1. The produced French word embeddings are available to the public, along with the fine-tuning code on the NLU tasks2. and the demo code3Les représentations distribuées de mots sont couramment utilisées dans de nombreuses tâches de traitement du langage naturel, en ajoutant que les vecteurs de mots pré-entraînés sur d'énormes corpus de textes ont atteint une performance importante dans de nombreuses tâches NLP. Cet article présente plusieurs vecteurs de mots de qualité supérieure pour la langue française, deux d'entre eux étant entraînés sur des données françaises massives recueillies au cours de cette étude et les autres sur un corpus français déjà existant utilisé pour pré-entraîner le model FlauBERT. Nous évaluons également la qualité de nos vecteurs de mots proposés et des vecteurs de mots français existants sur la tâche d'analogie de mots français. De plus, nous effectuons l'évaluation sur de multiples tâches NLU qui montrent l'amélioration importante des performances des vecteurs de mots pré-entraînés durant cette étude par rapport aux plongements existants et aléatoires. Enfin, nous avons créé une application web pour tester et visualiser les plongements de mots obtenus 1. Ceux derniers sont disponibles au public, ainsi que le code d'affinage sur les tâches NLU 2. et le code de la démonstration 3