Two simple, sensitive and extraction-free spectrophotometric methods are described for the estimation of risperidone (RSP) in both pure and in pharmaceutical preparations. The proposed methods are based on the formation of ion-pair complex between RSP and the dyes, bromophenol blue (BPB) in method A and Phenol red (PR) in method B at room temperature to form yellow colored products which show maximum absorbance at 410 and at 400 nm in methods A and B, respectively. Beer's law was obeyed in the concentration range of 0.5-10 and 0.5-25 μg mL-1 in methods A and B with apparent molar absorptivities of 3.43 × 104 and 0.85 × 104 L moL-1 cm-1, respectively. The limit of detection for method A is found to be 0.0056 and for method B is 0.132 μg mL-1. The composition of the ion-pairs was established by Job’s method and it was found to be 1:1 for both the methods A and B. The proposed methods have been applied successfully to the determination of RSP in pharmaceutical preparations. The results were statistically compared with those of a reference method by applying the Student’s t-test and F-test. The methods developed were validated for accuracy and precision by performing recovery experiments via standard addition technique
A series of new N-(substituted)-1-methyl-2,4-dioxo-1,2-dihydroquinazoline-3(4H)-carboxamides were designed, synthesized, and evaluated for their anticonvulsant activity. Most of the synthesized compounds exhibited potent anticonvulsant activities in the maximal electroshock (MES) and pentylenetetrazol (PTZ) test. The most promising compound 4c showed significant anticonvulsant activity with a protective index value of 3.58. The compounds 4a-c were also found to have encouraging anticonvulsant activity in the MES and PTZ screen when compared with the standard drugs, valproate and methaqualone. The same compounds were found to exhibit advanced anticonvulsant activity as well as lower neurotoxicity than the reference drugs.
ree simple, sensitive, accurate, and rapid visible spectrophotometric methods (A, B, and C) have been developed for the estimation of nitrazepam in both pure and in pharmaceutical preparations. ey are based on the diazotization of reduced nitrazepam with nitrous acid followed by coupling with acetyl acetone (method A), diphenylamine (method B), and citrazinic acid (method C) to form colored azo-dyes, exhibiting absorption maxima (max) at 400, 550, and 460 nm, for methods A, B, and C, respectively. e produced colored azo-dyes are stable for more than 2 h. Beer's law was obeyed in the concentration range of 0.5-20, 0.3-14 and 0.5-12 g/mL for methods A, B, and C, respectively and the corresponding molar absorptivity values are 1.01 × 10 4 , 1.00 × 10 4 , and 1.51 × 10 4 L mol −1 cm −1. All variables have been optimized and the results were statistically compared with those of a literature method by employing the Student's t-test and F-test. No interference was observed from common adjuvants normally added to the tablets. e results obtained in the proposed methods are in good agreement with labeled amounts, when marketed pharmaceutical preparations are analyzed, which could be applied in the routine quality control analysis laboratory.
A rapid, simple, and sensitive spectrophotometric method has been described for the determination of nimodipine in bulk drug, tablets, and injection. The proposed method is based on the diazotization of reduced nimodipine with nitrous acid followed by coupling with phloroglucinol to form colored azo dye and showing absorption maximum () at 410 nm. The formed colored azo dye is stable for about more than 2 h. The method obeyed Beer’s law over the concentration range of 0–25 μg/mL and the corresponding molar absorptivity value is L/moL/cm. The Sandell sensitivity values limits of detection (LOD) and quantification (LOQ) values have also been reported for the developed method. The accuracy and precision of the method was evaluated on intra- and interday basis; the relative error (%RE) and the relative standard deviation (RSD) were <2.0%. All variables have been optimized and the presented reaction sequence was applied to the analysis of nimodipine in bulk drug, tablets, and injections. The performance of this method was evaluated in terms of Student’s -test and variance ratio -test to find out the significance of proposed method over the reference method.
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