Determination of Labetalol Hydrochloride in Drug Formulations by Spectrophotometry

A validated, selective and sensitive spectrophotometric method has been developed for the determination of labetalol hydrochloride in commercial dosage forms. The method is based on the coupling reaction of positive diazonium ion of 4‐aminobenzenesulfonic acid with phenolate ion of labetalol to form a colored azo compound which absorbs maximally at 395 nm. Under the optimized experimental conditions, the color is stable up to 2 h and Beer's law is obeyed in the concentration range of 0.8–17.6 μg mL^?1 with a linear regression equation of A = 4.84 × 10^?4 + 7.864 × 10^?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity and Sandell's sensitivity are found to be 2.874 × 10⁴ L mol^?1 cm^?1 and 0.013 μg cm^?2 per 0.001‐absorbance unit, respectively. The limits of detection and quantitation of the proposed method are 0.08 and 0.23 μg mL^?1, respectively. The intra‐day and inter‐day precision variation and accuracy of the proposed method is acceptable with low values of standard analytical error. The recovery results obtained by the proposed method in drug formulations are acceptable with mean percent recovery ± RSD of 99.97 ± 0.52 ‐ 100.03 ± 0.63%. The results of the proposed method compared with those of Bilal's spectrophotometric method indicated excellent agreement with acceptable true bias of all samples within ± 2.0%.     

Kinetic Spectrophotometric Determination of Metoprolol Tartrate in Commercial Dosage Forms

A kinetic spectrophotometric method has been described for the determination of metoprolol tartrate in commercial dosage forms. The procedure is based on the reaction of the drug with 1‐chloro‐2, 4‐dinitrobenzene (CDNB) in dimethylsulfoxide (DMSO) at 100 ± 1 °C. The reaction is investigated by measuring the change in absorbance with time at 420 nm. Fixed‐time (ΔA) and equilibrium methods are chosen for obtaining the calibration curves. Both calibration curves were found to be linear over the concentration range of 5‐60 μg mL^?1. The regression analysis of calibration data resulted in the linear regression equations of ΔA = ?1.608 × 10^?4 + 3.96 × 10^?3 C and A = 7.31 × 10^?4 + 1.90 × 10^?2 C for fixed time (ΔA) and equilibrium methods, respectively. The limit of detection (LOD) for fixed time and equilibrium methods are 1.16 and 0.415 μg mL^?1, respectively. The method has been successfully applied to the quantitation of metoprolol tartrate in commercial dosage forms. Statistical comparison of the results shows that there is no significant difference between the proposed methods and El‐Ries's spectrophotometric method.     

Colorimetric and Bromometric Determination of Pirbuterol Hydrochloride

Abstract

Two proposed methods are reported for the quantitation of pirbuterol hydrochloride, namely, (i) colorimetric and (ii) titrimetric methods. The colorimetric method is based on coupling betweem diazotized sulphanilamide and pirbuterol hydrochloride. Under the optimum conditions studied, the coupling product exhibits a maximum at 440 nm. Linear relation between absorbance, A, and concentration of pirbuterol hydrochloride is in the range 5–40 μgml^?1. The mean percentage obtained for capsules (Exirel^R ?15 mg) was 100.8 ± 0.7 whereas mean percentage recovery obtained for the authentic drug was 100.5 ± 0.8.

The titrimetric procedure involves bromination of authentic pirbuterol in acid medium and residual titration of excess bromine. The stoichiometry of the reaction was investigated and infra-red analysis, of the bromoderivative was carried out. When applied to capsules the bromometric method gave mean percentage of 100.18 ± 2.25.     

Selective Kinetic Spectrophotometric Determination of Nitrite in Food and Water

Abstract

A highly selective and sensitive method for the kinetic spectrophothometric determination of sub-microgram amounts of nitrite has been development based on its reaction with Nile blue 2B in acidic medium. The reaction is monitored spectrophotometrically at 595 nm at a fixed time of 4.5 min. The change in absorbance at 595 nm is related to the concentration of nitrite in the range 0.005 - 1.100 μg.ml^?1 The detection limit is 0.001 μg.ml^?1. The relation standard deviation is 1% for 0.020 μg.ml^?1 of nitrite for ten replicate measurements. Most common anions and cations do not interfere. The procedure was applied to the determination of trace amounts of nitrite in sausage and water.     

Kinetic spectrophotometric methods for the determination of dothiepin hydrochloride in bulk and in drug formulation

Two simple and sensitive kinetic methods for the determination of dothiepin hydrochloride are described. The first method is based on kinetic investigation of the oxidation reaction of the drug with alkaline potassium permanganate at room temperature for a fixed time of 25 min. The absorbance of the colored manganate ions is measured at 610 nm. The second method is based on the reaction of dothiepin hydrochloride with 4-chloro-7-nitrobenzofurazan (NBD-Cl) in the presence of 0.1 mol L^–1 sodium bicarbonate. Spectrophotometric measurement was achieved by recording the absorbance at 470 nm for a fixed time of 60 min. All variables affecting the development of the color were investigated and the conditions were optimized. Plots of absorbance against concentration in both procedures were rectilinear over the ranges 4–24 and 50–250 g mL^–1, with mean recoveries 99.33±0.42 and 99.88±0.53, respectively. The proposed methods were successfully applied for the determination of dothiepin hydrochloride in bulk powder and in capsule dosage form. The results obtained were found to agree statistically with those given by the non-aqueous B.P. method. Furthermore the methods were validated according to USP guidelines and also assessed by applying the standard addition technique. The determination of dothiepin hydrochloride by the fixed concentration method is feasible with the calibration equations obtained, but the fixed time method proves to be more applicable.     

Development and Validation of Kinetic Spectrophotometric Method for the Determination of Losartan Potassium in Pure and Commercial Tablets

A validated kinetic spectrophotometric method has been developed for the determination of losartan potassium in pure and dosage forms. The method is based on oxidation of the losartan potassium with alkaline potassium permanganate at room temperature (25 ± 1 °C). The reaction is followed spectrophotometrically by measuring the increase in absorbance with time at 603 nm, and the initial rate, fixed time (at 12.0 min) and equilibrium time (at 90.0 min) methods are adopted for constructing the calibration graphs. All the calibration graphs are linear in the concentration range of 7.5–60.0 μg mL^?1 and the calibration data resulted in the linear regression equations of n? = ?6.422 × 10^?7 + 1.173 × 10^?5 C, A =3.30 × 10^?4 + 5.28 × 10^?3 C and A = ?2.09 × 10^?2 + 1.05 × 10^?1 C for initial‐rate, fixed time and equilibrium time methods, respectively. The limits of detection for initial rate, fixed time and equilibrium time methods are 0.71, 0.21 and 0.19 μg mL^?1, respectively. The activation parameters such as E_a, ΔH^?, ΔS^?, and ΔG^? are also determined for the reaction and found to be 87.34 KJ mol^?1, 84.86 KJ mol^?1, 50.96 JK^?1 mol^?1 and ?15.10 KJ mol^?1, respectively. The variables are optimized and the proposed methods are validated as per ICH guidelines. The method has been applied successfully to the estimation of losartan potassium in commercial tablets. The performance of the proposed methods was judged by calculating paired t‐ and F‐ values. The analytical results of the proposed methods when compared with those of the reference method show no significant difference in accuracy and precision and have acceptable bias.     

Quantitation of Diltiazem Hydrochloride in Commercial Dosage Forms by Visible Spectrophotometry

A selective and sensitive visible spectrophotometric method has been described for the quantitation of diltiazem hydrochloride in commercial dosage forms. The method is based on the reaction of the tertiary amino group of the drug with sodium hypochlorite to form the chloro drug derivative, followed by the destruction of the excess hypochlorite by sodium nitrite and the subsequent development of blue color takes place by the reaction of chloro derivative of drug with starch and potassium iodide in sodium bicarbonate medium. The maximum absorbance of the resulting blue solution is read at 540 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 2.5–25.0 μg mL^?1 with a linear regression equation of A = 9.85 × 10^?4 + 4.90 × 10^?2 C and coefficient of correlation, r = 0.9999. The molar absorptivity is found to be 2.26 × 10⁴L mol^?1 cm^?1. The limits of detection and quantitation of the proposed method are 0.12 and 0.37 μg mL^?1, respectively. The proposed method has been successfully applied for the quantitation of diltiazem hydrochloride in commercial dosage forms. The results of the proposed method compared with those of Abdellatef's spectrophotometric method presented good mean recovery with acceptable true bias of all pharmaceutical samples within ± 2.0%.     

Assay of Phenformin Hydrochloride in Pharmaceutics by Coupling with Sodium Nitroprusside

A novel and simple spectrophotometric method for the determination of phenformin hydrochloride using sodium nitroprusside as chromogenic reagent is developed in this paper. The experiment indicates that the sodium nitroprusside can react with the phenformin hydrochloride in a basic solution to form a product with colored N‐nitrosamines. The stoichiometric ratio of phenformin hydrochloride and sodium nitroprusside is 1:3 in the product. The maximal absorption wavelength (λ_max) of the product is 520 nm, ?₅₂₀ = 2.2 × 10³ Lmol^?1cm^?1. A Good linear relationship is obtained between the absorbance (A) and the concentration (C) of phenformin hydrochloride in a wide range of 0.20‐400 μg mL^?1. The equation of the linear regression is A = 0.03461 + 0.00907C (μg mL^?1) with a linear correlation coefficient of 0.9991. The detection limit is 0.13 μg mL^?1, and the relative standard deviation (R.S.D.) is 0.19%. The method is successfully applied to the determination of phenformin hydrochloride in tablet forms, and satisfactory recoveries are obtained.     

Colorimetric Microdetermination of Bromhexine Drug in Aqueous Solution

A simple, accurate and sensitive method for determination of bromhexine hydrochloride drug in aqueous solution has been described. The procedure has been based on the reaction of this drug with an excess amount of p‐dimethylaminobenzaldehyde (DAB) in acidic medium (pH =1.6) and the presence of sodium dodecyl sulfate (SDS). The produced yellow color from this reaction has been followed spectrophotometrically at an absorbance maximum of 430 nm. Microgram amounts of bromhexine hydrochloride can be estimated with an accuracy of better than ±1.5% and a relative standard deviation of less than 3.5%. The method has been used for the determination of 0.41–82.5 μg.mL^?1 with a molar extinction coefficient of 4699.1–3602.3 L.mol^?1.cm^?1. An application of the developed procedure to bulk bromhexine hydrochloride and some of its pharmaceutical preparations has been carried out. The effect of the presence of some other surfactants and common pharmaceutical additives has been investigated. A comparison of the presented method with that in the absence of SDS and the standard method of the British Pharmacopoeia has been explored. The suggestion, according to the results, is to use the developed method as standard in pharmaceutical applications.     

Spectrophotometric Determination of Etilefrine,Ritodrine, Isoxsuprine and Salbutamol by Nitration and Subsequent Meisenheimer Complex Formation

Abstract

A simple and sensitive colorimetric method has been developed for the determination of four phenolic drugs, namely, etilefrine hydrochloride, ritodrine hydrochloride, isoxsuprine hydrochloride and salbutamol sulphate. The method is, mainly, based on the nitration of the drug molecule followed by the subsequent formation of meisenheimer complex with a nucleophilic reagent (acetone) in alkaline medium. The experimental conditions leading to optimum chromogen intensity and stability were carefully studied and incorporated in the general procedure. Under the proposed conditions, the method was applicable over the concentration range of 4.8–16 μg ml^?1 for the four drugs. The suggested method was further applied for the determination of the studied drugs in bulk and pharmaceutical dosage forms. The results of the analysis were found to agree statistically with those obtained with either the official or the referee methods. The procedure is characterized by its simplicity with accuracy and precision.     

A predictive-kinetic method for the quantitation of amino acids with ninhydrin

The development and evaluation of a predictive-kinetic method for quantifying amino acids based on reactions with ninhydrin are described. Conditions are developed for which reactions are pseudo-first-order in the amino acid. Absorbance vs. time data from the kinetic region of the reaction (1–3 half-lives) are fitted to a first-order model to predict the total absorbance change that would occur if the reaction were monitored to completion. Computed absorbance changes vary linearly with amino acid concentration between 1 × 10^?5 and 5 × 10^?5 mol l^?1. Results are virtually independent of changes in temperature (± 1° C) and ninhydrin concentration (± 3 × 10^?3 mol l^?1).     

Utility of p-chloranilic Acid and 2,3 Dichloro-5,6-dicyano p-Benzoquinone (DDQ) for the Spectrophotometric Determination of Triamterene

Abstract

Two simple and sensitive spectrophotometric procedures are suggested for analysis of triamterene. The first procedure is based on the reaction of triamterene with p-chloranilic acid (p-CA) in methylene chloride to form a highly stable coloured product, exhibiting maximum absorbance at λ 530 nm. Beer's law is obeyed in the range of 40–220 μg.ml^?1 with a mean percentage accuracy of 99.98 ± 0.446. Limit of determination is 20 μg.ml^?1. In the second procedure, the drug is determined via charge transfer complex formation with 2,3 dichloro-5,6-dicyano p-benzoquinone (DDQ) using methylene chloride as a solvent. Here the reaction product has two well defined maxima at 460 nm and 530 nm where each has been utilized for quantitative determination. Beer's law is obeyed in concentration ranges of 25–125 μg.ml^?1 and 25–150 μg.ml^?1 with mean percentage accuracies of 99.92 ± 0.449 and 100.00 ± 0.511 for both maxima. 460 and 530 nm. respectively. Limit of determination is 12.5 μg.ml^?1 at both maxima. Optimum conditions for each procedure have been studied and the stoichiometry of both reactions was ascertained using Job's method of continuous variation. The validity of the suggested procedures was assessed by applying the standard addition technique using the drug capsules. Both procedures are statistically analyzed as compared with BP method for analysis of triamterene (non aqueous titration) revealing good accuracy and precision as indicated by t and F tests.     

Post‐chemiluminescence Method of the Determination of Loperamide Hydrochloride in Human Plasma and Pharmaceutical by Using Dichlorofluorescein as Chemiluminescence Reagent

Abstract

A post‐chemiluminescence (PCL) was observed when loperamide hydrochloride solution was injected into the reaction mixture after the finish of CL reaction of alkaline N‐Chlorosuccinimide (NCS) and dichlorofluorescein. Based on this phenomenon, a simple, sensitive and fast flow injection PCL method was established for the determination of loperamide hydrochloride. The possible mechanism for the PCL reaction was discussed via the investigation of the CL kinetic characteristics, the CL spectra, the fluorescence spectra. The PCL intensity responded linearly to the concentration of loperamide hydrochloride in the range 8.0×10^?10 to 6.0×10^?7 g · ml^?1 with a linear correlation of 0.9995. The detection limit was 4×10^?10 g · ml^?1. The relative standard deviation was 2.4% for 4.0×10^?8 g · ml^?1 loperamide hydrochloride (n=11). This method has been applied to the determination of loperamide hydrochloride in human plasma and pharmaceutical samples with satisfactory results.     

New,simple and validated kinetics spectrophotometric method for determination of moxifloxacine in its pharmaceutical formulations

The objective of this research was to develop a kinetic spectrophotometric method for determination of moxifloxacine (MOXF) in pure form and pharmaceutical formulations. The method was based on the formation of a colored N-vinyl chlorobenzoquinone derivative of MOXF by its reaction with 2,3,5,6-tetrachloro-1,4-benzoquinone in presence of acetaldehyde.The formation of the colored product was monitored spectrophotometrically by measuring the absorbance at 652 nm. Factors affecting the reaction were studied and optimized. The stoichiometry of the reaction was determined, and the reaction pathway was postulated. The activation energy of the reaction was calculated and found to be 6.65 kJ mol^?1. Under the optimized conditions, the initial rate and fixed time (at 5 min) methods were utilized for constructing the calibration graphs. The graphs were linear in concentration ranges 5–100 and 15–150 μg ml^?1 with limit of detection of 2.0 and 5.0 μg ml^?1 for the initial rate and fixed time methods, respectively. The analytical performance for both methods was fully validated, and the results were satisfactory. No interference was observed from the excipients that are commonly present in the pharmaceutical formulations. The proposed method was successfully applied to the determination of MOXF in its pharmaceutical formulations. The label claim percentages were 101.25 ± 0.73% and 100.92 ± 0.65% for the initial rate and fixed time method, respectively. Statistical comparison of the results with those obtained by a reference spectrophotometric method showed excellent agreement between the accuracy and precision of the two methods. The proposed method has great value in its application to the analysis of MOXF in quality control laboratories.     

Kinetic Spectrophotometric Analysis and Spectrofluorimetric Analysis of Ciprofloxacin Hydrochloride and Norfloxacin in Pharmaceutical Preparations Using 4‐Chloro‐7‐Nitrobenzo‐2‐Oxa‐1,3‐Diazole (NBD‐Cl)

Simple, reliable, sensitive and accurate kinetic spectrophotometric and spectrofluorimetric methods were proposed for the determination of ciprofloxacin hydrochloride (CPX) and norfloxacin (NRX) in pure form and in pharmaceuticals. The methods are based on coupling the studied drugs with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) in the presence of alkaline borate buffer. Spectrophotometric measurement was achieved by recording the absorbance at 477 nm after a fixed time of 20 and 15 min on a water bath adjusted at 70 ± 1 °C for CPX and NRX, respectively. The same product exhibited emission peaks at 540 nm. The different experimental parameters affecting the development and stability of the color were carefully studied and optimized. The absorbance concentration plots were linear over the ranges 3‐18 and 2.5‐15.0 μg/mL for CPX and NRX, respectively, while the fluorescence concentration plots were linear over the ranges 0.06‐0.36 and 0.05‐0.30 μg/mL for CPX and NRX, respectively. The limit of detection of the kinetic method was about 0.2 μg/mL for both drugs while the fluorescence measurement enabled their detection at a concentration of about 0.012 μg/mL. The proposed methods were successfully applied for the assay of the two drugs in their commercial products. The results obtained were statistically compared with those obtained by reference HPLC and spectrophotometric methods. The stoichiometry of the reaction was determined and the reaction pathway was postulated.     

Kinetic Spectrophotometric Determination of Nitrite with Tropaeolin 00-Bromate System

A simple accurate kinetic spectrophotometric method was developed for the determination of nitrite based on its catalytic effect on the redox reaction between tropaeolin 00 and bromate in acid medium. Nitrite was determined by measuring the decrease in the absorbance of tropaeolin 00 at 530 nm by a fixed time method, after 30 s from the initiation of the reaction. The calibration graph was linear in the range 6–500 ng mL^?1 of nitrite and the detection limit was 2 ng mL^?1. The proposed method is selective and is useful for the determination of nitrite in drinking water samples.     

Kinetic-Spectrophotometric Determination of Molybdenum(VI) Based on Its Catalytic Effect on the Thionine-Hydrazine Reaction

Abstract

A kinetic method for the determination of trace amounts of Mo(VI) (0.05-4 μg ml^?1) based on its catalytic effect on the reduction of thionine by hydrazine monochloride in strongly acidic media is reported. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of thionine at 605 nm after a fixed time (5 min.). The detection limit of the method is 23 ng ml^?1 and the relative standard deviation (RSD) for 0.05 μg ml^?1 of Mo(VI) is 1.2% (n=7). The method is almost free from interferences, especially from large amounts of tungsten. The procedure was successfully applied to the determination of trace amounts of molybdenum in steel.     

Kinetic Method for the Determination of α‐Methyldopa in Pharmaceutical Preparations: Analytical Procedure and Reaction Mechanism Considerations

Abstract

A reliable and very simple kinetic method is proposed for the determination of α‐methyldopa in pharmaceutical preparations. It is based of the oxidation of α‐methyldopa, a catechol derivative, to quinone, by the ferric ion in the presence of salicylic acid and HCl. The deep blue complex formed between iron(III) and salicylate (λ_max 525 nm) allows the reaction to be watched as absorbance decreases with the reduction of the ferric ions to ferrous with the consequent dissociation of the complex. Four pharmaceutical preparations were analyzed and the results were compared with those obtained with the spectrophotometric United States Pharmacopeia method. The statistical t‐Student and the F‐tests were applied to compare the results obtained with the two independent methods. In all cases complete agreement, in terms of accuracy and precision, was observed with a confidence level of 95% (α=0.05). Considering the four samples analyzed, using the proposed method, and five determinations for each sample, the observed mean relative standard deviation (RSD) is about 0.8%. The concentration range studied was from about 2×10^?4 mol L^?1 to 18×10^?4 mol L^?1 (about 40 µg/mL to 360 µg/mL) in the final solution and it is quite adequate for the analytical procedure at 25.0±0.1°C. A typical coefficient of determination, r², of the calibration curve, is 0.9994. For the kinetic pseudo first order curves a typical observed r² is 0.99998. The Arrhenius activation energy was found to be 84.2±3.4 kJ mol^?1. A schematic mechanism of the reaction is proposed.     

Flow‐Injection Chemiluminescence Analysis of Cloperastione Hydrochloride

Abstract

A new chemiluminescence (CL) reaction was observed when cloperastine hydrochloride was injected into the reaction mixture after the CL reaction of Ce(IV) and sodium sulfite finished. A new flow injection CL method for the determination of cloperastine hydrochloride was established based on the CL reaction. The relative standard deviation (RSD) for the determination of cloperastine hydrochloride was 1.3% (n=11, c=1.0×10^?6 g/mL). The CL intensity responded linearly to the concentration of cloperastine hydrochloride in the range 2.0×10^?7～2.0×10^?5 g/mL (r=0.9962). The detection limit was 5×10^?8 g/mL cloperastine hydrochloride. The method had been applied to the determination of cloperastine hydrochloride in tablets with satisfactory results.     

Spectrophotometric Determination of Acebutolol Hydrochloride and Nicoumalone with Metol and Potassium Permanganate

Abstract

A spectrophotometric method is described for the determination of Nicoumalone and Acebutolol hydrochloride based on the formation of molecular complex with the reduction product of Nicoumalone or hydrolysis product of Acebutolol hydrochloride and p-N-methyl benzoguinone monoimine [formed in situ from met01 (p-N-methylaminophenol sulfate) and potassium permanganate, PMBQMI] at pH 3.3. Quantitative measurements were made at the maximum absorption of 525 nm. Beer's law is obeyed in the range of 5–50 μg ml^?1 and 5–60 μg ml^?1 for Nicoumalone and Acebutolol hydrochloride respectively. The proposed method is comparable with the reference method when applied to pharmaceutical preparations, and tablets, An average percentage recovery of 99.5 ± 0.8 was obtained.