First Derivative Spectrophotometric Determination of Phenytoin

Abstract

The first derivative curve (D₁) of absorption spectrum of Phenytoin in buffer pH 10 develos negative peaks at 244, 263 and 270 nm. D₁ at 244 nm was found linearly related to concentration over a range 0.4 ? 1.4 mg per 100 ml and highly reproducible (C.V. %=0.62). Tablets and capsules have been analyzed using D₁ at 244 nm and the mean percentage found were 99.7 ± 0.81 and 103.3 ± 0.44, respectively. The B.P. method gave 100.9 and 103.8 %, respectively.     

Analysis of Pheniramine Naleate and Cblorpheniramine Maleate Via Their Fe (III) Cohplexes

Abstract

A new spectrophotoraetric method has been developed for the analysis of pheniramine maleate and chlorphenlramine maleste, based on their reaction with iron (III). Pheniramine maleate and ch lor pheniramine maleate were found to form a 2:1 complex with iron (III) with an average log. stability constant of 12.26 and 12.36, respectively. The iron (III) complexes of both drugs showed maximum absorption at 273 nm, at pH 5, with slopes equal to 0.710 and 0.898 for pheniramine maleate complex and chlorpheniramine maleate complex, respectively. The proposed method was used for the determination of pheniramine maleate and chlorpheniramine maleate in quantities ranging between 0.25 × 10^?4 M to 2.5 × 10^?4 M with mean percentage recoveries of 100.17 ± 1.09% and 100.00 ± 1.13% for both drugs, respectively. The results obtained were compared with that of the B.P. (1980) method.     

Voltammetric Determination of Rosiglitazone in Pharmaceutical Preparations and Human Plasma

Abstract

The voltammetric behavior of rosiglitazone was studied using direct current (DC_t), differential pulse (DPP), and alternating current (AC_t) polarography. The drug manifests cathodic waves over a pH range of 2–11.2. In Britton‐Robinson buffer (BRb; pH 4), the diffusion current–concentration relationship was found to be rectilinear over a range of 4–24 µg · mL^?1 and 0.1–16 µg · mL^?1 using DC_t and DPP modes, respectively, with minimum limits of detection (LOD) of 0.15 µg · mL^?1 and 0.07 µg · mL^?1 using the DC_t and DDP modes, respectively. The diffusion‐current constant (I _d) was 6.63±0.03 (n=5). The proposed method was successfully applied to the determination of the studied compound both in pure form and in formulations. The mean percentage recoveries in tablets were 100.09±1.18 and 100.85±0.88 (n=5) using DC_t and DPP modes, respectively. Furthermore, the proposed method, adopting the DPP mode, was applied to the determination of rosiglitazone in spiked human plasma and the obtained mean percentage recoveries were 99.14±3.29 (n=4).     

Spectrophotometric Determination of Ipratropium Bromide in Liquid for Nebulization

ABSTRACT

Three simple and sensitive spectrophotometric methods for the determination of ipratropium bromide (IPB) in liquid for nebulization are described. Method A, is based on the formation of a charge transfer complex with iodine. The reaction product is measured spectrophotometrically at 278 nm. Method B, is based oh the formation of an ion – association complex between the drug and an acidic dye, Bromocresol green (BCG), which is extractable into chloroform and has an absorption maximum at 418 nm. Method C, uses derivative spectrophotometry for the determination of IPB by measuring the D₂-value at 232 nm. Beer's law is obeyed over the concentration range 1-10, 2-16 and 5-30 μg ml^? for method A, B and C, respectively. The optimum conditions for the formation of the charge transfer or ion-association complexes were optimized. The proposed methods were applied for the determination of IPB in liquid for nebulization. Evaporation to dryness and extraction of the residue with isopropanol, were performed before application of methods A & B. Mean percentage recoveries were found to be 99.67 ± 0.79, 99.26 ± 1.06 and 100.21 ± 0.85 for method A, B, and C, respectively.     

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.     

Successive Determination of Picogram Amounts of Phosphorus and Arsenic in Pure Water by Indirect Flameless Atomic Absorption (Mo) Spectroscopy

Abstract

The method involves the conversion of the P and As into the yellow 12-molybdo-phosphate or - arsenate complex, respectively, extraction into butyl acetate (in the case of As - with the preliminary addition of ethanol), the decomposition of the heteropoly-compounds with aqueous NH₃ and the back extraction of the liberated Mo into aqueous solution, for flameless AA determination. 10 pg P and 25 pg As in 0.4 ml samples of ultrapure water were determined with percentage errors below ±30%.     

Spectrofluorometric Determination of Drotaverine Hydrochloride in Pharmaceutical Preparations

Abstract

A highly sensitive, spectrofluorometric method was developed for the determination of drotaverine HCl in pharmaceutical preparations. The proposed method is based on the measurement of the native fluorescence of the drug in 0.1 M H₂SO₄ at emission 465 nm after excitation at 295 nm. The relative fluorescence intensity-concentration plot was rectilinear over the range of 0.16–4 µg·ml^?1, with good correlation (r = 0.9999) and a lower limit of detection (LOD) of 0.032 µg·ml?1. The proposed method was successfully applied for the determination of drotaverine HCl in tablets and ampoules with a recovery percentage of 100.42 ± 0.601,99.83 ± 0.82 and 99.43 ± 1.08, respectively, which were in accordance with those obtained by a compendial method.     

Colorimetric and Polarographic Methods of Analysis for Prenalterol Hydrochloride

Abstract

Two proposed methods have been described for the determination of prenalterol hydrochloride in acetate buffer (pH=4.1) as authentic material and in tablets form using a (i) colorimetric method based on reduction of ferric iron by prenalterol hydrochloride and subsequent measurement at 511 nm of the red color obtained by the treatment of the resultant ferrous iron with 1, 10-orthophenanthroline, (ii) a differential pulse polarographic method based on nitrosation with 0.1 M NaNO₂/dil. HC1 and consequent recording of the differential pulse polarogram. The differential polarogram was obtained under constant amplitude pulses of 50 mV (DP 50) superimposed on a linearly increasing DC-voltage ramp. The peak height (h), of the polarogram was measured at the peak potential of -0.2V on the dropping mercury electrode (DME) versus Ag/AgCl reference electrode. The linearity ranges observed are 0.6μgfml to 6.0μg/ml and 2μg/ml to 12μg/ml, respectively. The mean percentage recoveries for an authentic sample are 99.5±1.4 and 100.5±0.7, respectively. When applied to tablets claimed to contain 10 mg each, the mean percentages obtained are 99.7±2.3 and 100.6 ±1.5 respectively.     

Kinetic study of the fast step of the alkaline hydrolysis of p-chloranil using stopped flow technique

The alkaline hydrolysis of p-chloranil or 2,3,5,6-tetrachloro-1,4-benzoquinone (C₆Cl₄O₂, Q) was studied, using stopped flow spectrophotometry and Electron Spin Resonance techniques (E.S.R.). In the present study it was shown for the first time, that a free radical is produced chemically and that it can account for the propagation of the reaction. It was found that in alkaline conditions chloranil in a “Michael” fashion undergoes 1,2 addition being hydrolyzed and in turn produces a chloranil free radical (Q^•) The hydrolysis then proceeds via a number of intermediates yielded by this radical and a number of different products is formed. The formation of these products, both quantitatively and qualitatively has a strong dependence on the concentration of the OH⁻ species and chloranil. The various possible routes of the hydrolysis are studied either spectrophotometrically or by E.S.R. Two different intermediates are observed absorbing at 426 nm and at 540 nm, respectively. Each species was formed and destroyed within 10 s to 30 min depending on the exact conditions. The reaction rate constants for the formation and the decay of the intermediates was estimated using the Guggenheim method. At both wavelengths the rate constants seem to have a complex relation to the concentration of the anion. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 385–391, 1997     

Spectrophotometric determination of microgram amounts of vitamin B1 with chloranil

Vitamin B₁ (20–200 μg) is determined spectrophotometrically using chloranil as π-acceptor at pH 9. The method is relatively rapid (10 min standing time), simple (the reaction occurs at room temperature), precise (RSD = 1.7%), and relatively accurate (error ⩽ ±3.0%).     

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.     

Spectrophotometric Analysis of Systems with Non-Additive Absorbances

Abstract

The increment method under least squares has been applied to the spectrophotometric determination of p-hydroxybenzoic acid complexed with polyvinylpyrrolidone in water. The mean percentage recovery for six prepared mixtures was found to be 99.49 + 1.25. When the A_max method has been applied, the mean percentage recovery was found to be 90.99+5.59. The theoretical bases of the method have been discussed.     

Norfloxacin La(III)-based complex: synthesis,characterization, and DNA-binding studies

A La(III) complex, [La^IIICl₂(NOR)₂]Cl (2), containing norfloxacin (NOR) (1), a synthetic fluoroquinolone antibacterial agent, has been synthesized and characterized by elemental analysis, IR, UV–vis spectra and ¹H NMR spectroscopy, and molar conductance measurements. The interaction between 2 and CT-DNA was investigated by steady-state absorption and fluorescence techniques in different pH media, and showed that 2 could bind to CT-DNA presumably via non-intercalative mode and the La(III) complex showed moderate ability to bind CT-DNA compared to other La(III) complexes. The binding site number n, and apparent binding constant K_A, corresponding thermodynamic parameters ΔG^#, ΔH^#, ΔS^# at different temperatures were calculated. The binding constant (K_A) values are 0.23 ± 0.05, 0.56 ± 0.05, and 0.18 ± 0.08 × 10⁵ L mol^?1 for pH 4, 7, and 11, respectively. It was also found that the fluorescence quenching mechanism of CT-DNA by La(III) complex was a static quenching process.     

Spectrofluorimetric determination of melamine formaldehyde in solid and liquid forms and in wastewater

A new, simple and sensitive spectrofluorimetric method for determination of trace amount of melamine formaldehyde (MF) was developed. In phosphate buffer solution of pH 7.4 MF can remarkably quench the luminescence intensity of toluylene red (NR) at λ_em = 590 nm due to formation of NR-MF ion associate complex. The luminescence intensity of NR-MF complex was in proportion to the concentration of MF and used as photo probe for its determination. The dynamic range for the determination of MF is 7.5–52.5 ppm with detection limit of 4.4 ppm. The method is relatively free from interferences from coexisting substances and used successfully for the determining of MF in powder and liquid forms and in wastewater produced from MF industries. The average recoveries and standard deviations of 98.3 ± 0.6, 98.1 ± 0.6 and 97.3 ± 0.5% were achieved for determination of MF in solid, liquid forms and wastewater, respectively     

Spectrophotometric Determination of Some Pharmaceutically Active Amides and Imides

Abstract

The determination of nicotinamide, alloxan, saccharin, barbitone and theobromine is achieved by a simple and rapid spectrophotometric method. The proposed method depends on the bromine oxidation of the amide or imide functional groups with the formation of N - bromoamide or N - bromoimide respectively, having a positive bromine atom. The oxidation products oxidize iodide ions to iodine which is measured as its starch complex.

The method is suitable for the determination of : 0.08–0.4, 0.5–5, 20–80, 25–200 and 50–400 mg with a mean accuracy (P′ = 0.05) of 99.29 ± 1.39%, 101.36 ± 1.44 %, 101.28 ± 1.85 %, 99.94 ± 1.24 % and 100.82 ± 1.29 % for the mentioned compounds respectively.     

Application of charge transfer reaction in the pharmaceutical analysis——Determination of chlorhexidine acetate

A spectrophotometric method for the determination of chlorhexidine acetate is described. The reaction between chlorhexidine acetate and chloranil took place in an alcohol-acetone solution at room temperature. The composition of the charge transfer complex is 1:2. Beer's law is obeyed in the concentration range of 15--270 μg·mL-1 with correlation coefficient 0.9995. The apparent molar absorptivity is 2.21×103 L·mol-1·cm-1 at 412 nm. The method is accurate (with a recovery of 100±1.6%) and precise (RSD=1.0%). It was successfully applied to determine chlorhexidine acetate in suppository or disinfectant solution.     

The modes of complexation of benzimidazole with aqueous β-cyclodextrin explored by phase solubility, potentiometric titration, 1H-NMR and molecular modeling studies

The results of rigorous modeling of phase solubility diagrams, pH solubility profiles and potentiometric titrations revealed the following for benzimidazole (BZ) and BZ/β-CD complexation in aqueous solution: (a) the pK _a value of BZ estimated at 5.66 ± 0.08 was reduced to 5.33 ± 0.06 in the presence of 15 mM β-CD at 25 °C, thus indicating inclusion complex formation; (b) BZ forms soluble 1:1 and 2:1 BZ/β-CD complexes with complex formation constants K ₁₁ = 104 ± 8 M⁻¹ and K ₂₁ = 16 ± 6 M⁻¹; (c) protonated BZ forms only 1:1 complex with K ₁₁ = 42 ± 12 M⁻¹; (d) ¹H-NMR studies in D₂O showed significant upfield chemical shift displacements for inner cavity β-CD protons indicating inclusion complex formation, while (e) Molecular modeling of BZ-β-CD interactions in water clearly indicated complete inclusion of one BZ molecule into the β-CD cavity.     

High Performance Liquid Chromatographic Determination of Pirenzepine Dihydrochloride in Its Pharmaceutical Formulation

Abstract

A high-performance liquid chromatographic procedure for the determination of pirenzepine dihydrochloride as a bulk material and in its tablet dosage form (Gastrozepin^R) is presented. Normal phase liquid chromatography has been performed on a Micro-pack Si-10 column using ammonium hydroxide (28–30% NH₃) in methanol (0.75: 99.25% v/v) as mobile phase at a flow rate of 2 ml/min. Clobazam has been used as internal standard with retention times of 1.9 and 2.8 minutes for clobazam and pirenzepine dihydrochloride, respectively at 254 nm. Analytical calibration yields a linear relationship between 5 and 25 μg/ml, with correlation coefficient of 0.999. Tablets each labelled to contain 25 mg pirenzepine dihydrochloride give mean percentage found of 99.98 ± 0.4. A plot of logarithm of concentration against time for a solution in 6 N hydrochloric acid gives a straight line with a slope of - 0.197 day^?1. The proposed method is, therefore, a stability indicating method.     

Amperometric and Conductimetric Methods for Simultaneous Determination of Captopril and Bendroflumethiazide

Abstract

The mixture of captopril (antihypertensive) and bendroflumethiazide (diuretic) was assayed using conductimetric and amperometric methods. Each method was applied for the analysis of laboratory-made sample mixtures in authentic and dosage forms. For captopril, the amperometric and conductimetric methods gave mean percent recoveries of 100.2 ± 1.2 and 99.6 ± 1.2, respectively. These results have shown good agreement when compared with other methods in the literature. When applied to bendroflumethiazide the conductimetric method gave percent recovery of 98.5 ± 1.6 which agreed closely with the spectrophotometric pharmacopoeial method.

The pK₁ for captopril was determined potentiometrically at room temperature (25°C) in aqueous medium. The calculated value, based on Henderson equation was 3.78.     

POLAROGRAPHIC INVESTIGATION OF THE SYSTEMS ARSENIC(III)-TARTARIC ACID AND ARSENIC(III)-1,2-DIAMINO-CYCLOHEXANE-N,N,N′,N′-TETRAACETIC ACID (DCTA)

Abstract

The reactions between As(III), tartaric acid (H₂T)and DCTA were investigated polarographically. The conditional stability constants of As(III)-complexes at a given pH-value and variable ligand concentration were calculated from the change of the limiting currents. The optimum conditions for calculating stability constants from the current were also discussed. It was found that DCTA (H₄L)formed the complex [As(OH)₂HL]^2- whose overall formation constant was lgβ111=(20.67 ±0.09)atμ=0.1 and t°- (25.0±0.2)°C, whereas the complex between As(III) and H₂T was [As(OH)₂T]^? with an overall stability constant 1gβ 101= 6.62 ±0.14 at μ=0.1 and t°= (25 ± 0.2)°C.