Indirect spectrophotometric determination of propranolol hydrochloride and piroxicam in pure and pharmaceutical formulations.

Two simple and sensitive indirect spectrophotometric methods for the assay of propranolol hydrochloride (PPH) and piroxicam (PX) in pure and pharmaceutical formulations have been proposed. The methods are based on the oxidation of PPH by a known excess of standard N-bromosuccinimide (NBS) and PX by ceric ammonium sulfate (CAS) in an acidic medium followed by the reaction of excess oxidant with promethazine hydrochloride (PMH) and methdilazine hydrochloride (MDH) to yield red-colored products. The absorbance values decreased linearly with increasing concentration of the drugs. The systems obeyed Beer's law over the concentration ranges of 0.5 - 12.5 and 0.3 - 16.0 microg/ml for PPH, and 0.4 - 7.5 and 0.2 - 10 microg/ml for PX with PMH and MDH, respectively. Molar absorptivity values, as calculated from Beer's law data, were found to be 1.36 x 10(4) and 2.55 x 10(4) l mol(-1) cm(-1) for PPH, and 2.08 x 10(4) and 2.05 x 10(4) l mol(-1) cm(-1) for PX with PMH and MDH, respectively. The common excipients and additives did not interfere with their determinations. The proposed methods have been successfully applied to the determinations of PPH and PX in various dosage forms. The results obtained by the proposed methods compare favorably with those of official methods.     

HPLC Determination of Ritodrine Hydrochloride in Pharmaceutical Formulations

A simple, rapid, and accurate HPLC method is described for the determination of ritodrine hydrochloride (RTH) in both pure form and pharmaceutical formulations. A Hypersil Shendon ODS column with a mobile phase of dibasic phosphate buffer and acetonitrile (75 : 25) and isoxsuprine hydrochloride were used as an internal standard. The flow rate was 1 mL min^–1 and the effluent was monitored at 270 nm pH 4.0. The calibration graph is linear in the range 2–30 g mL^–1. The proposed HPLC method has been successfully employed for the determination of RTH in Yutopar tablets and injection solutions.     

Spectrophotometric estimation of ketotifen fumarate in pharmaceutical formulations

Four simple and sensitive spectrophotometric methods (A–D) for the determination of Ketotifen fumarate in bulk samples and pharmaceutical formulations are described. They are based on the formation of coloured species by the coupling of the diazotised sulphanilamide with the drug (method A, _max 520 nm) or by oxidizing it with excessN-bromo-succinimide and determining the consumed NBS with decrease in colour intensity of celestine blue (method B: _max 540 nm) or by the reduction of Folin-Ciocalteau reagent (method C: _max 720 nm) or by the formation of a chloroform-soluble, coloured ionassociation complex between the drug and Azocarmine G at pH 1.5 (method D: _max 540 nm). Regression analysis of Beer-Lambert plots showed good correlations in the concentration ranges 1–10, 2–12, 4–28 and 2.5–25 g/ml for methods A–D, respectively. The validity of the proposed methods was tested by analysing pharmaceutical formulations containing KTF: the relative standard deviations were within ±1.0%. Recoveries were 98.9–100.2%.     

Spectrophotometric determination of drugs in pharmaceutical formulations withN-bromosuccinimide and celestine blue

Simple, sensitive and selective methods are proposed for the spectrophotometric determination of drugs, viz., tetracycline HCl, nifurtimox, ethionamide, propranolol HCl and isonicotinic acid hydrazide, based on their reactivity withN-bromosuccinimide (NBS). The method involves the addition of excess NBS of known concentration in the presence of 0.25M HCl and the unreacted NBS is determined by the measurement of the decrease in the absorbance of the dye celestine blue (_max 540 nm), which was found to be the most suitable of several dyes tested. This method was applied for the determination of drug contents in pharamaceutical formulations and enabled the determination of the drugs in microgram quantities (0.2 to 5 g/ml). Standard deviations were typically 0.5mg per dose (RSD 0.1–1.0%). No interferences were observed from excipients and the validity of the method was tested against reference method. Recoveries were 99.8–101.1%.     

Spectrophotometric Determination of Antiallergic Drug in Bulk Powder and in Its Pharmaceutical Formulations

Two simple, rapid and selective spectrophotometric methods have been described for the determination of promethazine hydrochloride (PMH) either in pure or pharmaceutical formulations. The methods are based on the formation of a green colored product with sulphanilic acid (SPA) in presence of N-bromosuccinimide (NBS) or a red colored, chloroform soluble product with p-nitroaniline (PNA) in presence of ceric ammonium sulphate (CAS). The chromogen formed has maximum absorption at 600 nm and at 510 nm with SPA and PNA, respectively. The optimum reaction conditions and other analytical parameters are evaluated. Beer's law is valid in the concentration range of 0.5–25 g/mL (R= 0.9983) with SPA and 2–75 g/mL (R = 0.9981) with PNA. Molar absorptivity values as calculated from the Beer's law data are 5.54 × 10³ L/mol/cm and 3.05 × 10³ L/mol/cm for SPA and PNA, respectively. The results are in good agreement with those of the official method. No interference was observed from common pharmaceutical excipients.     

Three simple spectrophotometric methods for the determination of sulphinpyrazone

Three simple and sensitive spectrophotometric methods for the determination of sulphinpyrazone (SP) in bulk samples and pharmaceutical formulations are described. They are based on the oxidation of sulphinpyrazone with excess N-bromosuccinimide (NBS) and determination of the unconsumed NBS with metol-isonicotinic acid hydrazide (method A, lambda(max): 620 nm); by the reduction of Folin-Ciocalteu reagent (method B, lambda(max) 770 nm); or by the formation of a chloroform-soluble, coloured ion-association complex between the drug and Methylene Violet (MV) at pH 7.0 (method C, lambda(max) 545 nm).     

Utility of the ion-pair formation for spectrophotometric determination of terfenadine in pure form and in some pharmaceutical formulations

A spectrophotometric procedure for the determination of terfenadine and a number of its pharmaceutical preparations has been developed that offers advantages of simplicity, rapidity, sensitivity and stability indication over the official USP (1995) method. The proposed method is based on the formation of ion-pairs by the reaction of terfenadine with some chromotropic acid mono- and bis-azo dyes. Different variables affecting the ion-pair formation were studied and optimized. At the maximum absorption of 557, 521, 592 and 543 nm, Beer's law is obeyed in the range 0.2–18.6, 0.2–16.4, 0.2–25.0 and 0.2–22.2 g ml^–1 on using reagents I, II, III and IV, respectively. The stoichiometric ratio and stability of each ion-pair were estimated and the mechanism of the reaction is discussed. The molar absorptivity and Sandell sensitivity of the produced ion-pairs were calculated in addition to Ringbom optimum concentration ranges. Statistical treatment of the experimental results indicates that the procedures are precise and accurate. Excipients used as additives in pharmaceutical formulations did not interfere in the proposed procedures. The reliability of the methods was established by parallel determination against the official USP method. The procedures described were successfully applied to the determination of the bulk drug and its pharmaceutical formulations by applying the standard addition technique.     

Spectrophotometric determination of mebeverine hydrochloride

Three simple, sensitive and reproducible visible spectrophotometric methods (A-C) for the determination of mebeverine hydrochloride (MVH) in bulk samples and pharmaceutical formulations are described. Methods A and B are based on the formation of ion-association complexes between the drug and fast green FCF (FGFCF, _max 625 nm) or bromothymol blue (BTB, _max 405 nm). Method C is based on the formation of a molecular complex between the drug and cobalt thiocyanate (CTC, _max 625 nm). Regression analysis of Beer's plots showed good correlation in the concentration ranges 2–40, 2–25 and 100–600 g/ml for methods A, B and C respectively. No interference was observed from the usually existing additives in pharmaceutical formulations and the applicability of the methods was examined by analysing tablets containing MVH. Standard deviations were typically 0.75 mg per dose (RSD: 0.25–0.5%). Recoveries were 99.0–100.2%.     

Spectrophotometric determination of astemizole

Four simple and sensitive spectrophotometric methods for the determination of astemizole (AZ) in pure samples and pharmaceutical formulations are described. They are based on the oxidation of astemizole with excess N-bormosuccinimide (NBS) and determination of the unconsumed NBS with, metol-sulphanilamide (method A, lambda(max): 520 nm) or celestine blue (method B, lambda(max): 540 nm); or by the reduction of Folin-ciocalteu reagent (method C, lambda(max): 720 nm); or by the formation of a chloroform-soluble, coloured ion-association complex between the drug and azocarmine G (AG) at pH 1.5 (method D, lambda(max); 540 nm). The results obtained are reproducible with a coefficient of variation of less than 1.0%.     

RP-HPLC Determination of Famotidine and its Potential Impurities in Pharmaceuticals

A simple, sensitive, and rapid reversed-phase high-performance liquid chromatographic method has been developed for determination of famotidine (FMT) and its impurities in pharmaceutical formulations. Separations were performed on a Supelcosil LC18 column with an isocratic mobile phase—13:87 (v/v) acetonitrile–0.1 M dihydrogen phosphate buffer containing 0.2% triethylamine (pH 3.0). The mobile phase flow rate was 1 mL min^–1 and the detection wavelength was 265 nm. Response was linearly dependent on concentration between 1 and 80 g mL^–1 (regression coefficient, R², from 0.9981 to 0.9999). RSD from determination of method repeatability (intraday) and reproducibility (interday) were <2% (n=6). Lowest detectable concentrations ranged from 0.08 to 0.14 g mL^–1. The proposed liquid chromatographic method can be satisfactorily used for routine quality control of famotidine in pharmaceutical formulations.     

A sequential injection method for the determination of piroxicam in pharmaceutical formulations using europium sensitized fluorescence

A simple, selective and sensitive luminescence method for the assay of piroxicam (PX) in pharmaceutical formulation is developed. The method is based on the luminescence sensitization of europium (Eu³⁺) by complexation with PX. The signal for PX–EU is monitored at λ_ex=358 nm and λ_em=615 nm. Optimum conditions for the formation of the complex in methanol were 0.01 M TRIS buffer and 0.2 mM of Eu³⁺ which allows the determination of 100–2000 ppb of pX in batch method and 100–1000 ppb with limit of detection (LOD) = 23.0 ppb using sequential injection analysis (SIA). The relative standard deviations of the method range between 2 and 3% indicating excellent reproducibility of the method. The proposed method was successfully applied for he assay of PX in pharmaceutical formulations (Feldene capsules and tablets). Average recoveries of 101.0±0.3 and 98.8±2.7% were obtained for capsules in methanol using batch and sequential injection (SI) methods, respectively.     

Extraction-spectrophotometric determination of amprolium hydrochloride using bromocresol green, bromophenol blue and bromothymol blue

A new procedure for the determination of amprolium hydrochloride by reaction with bromocresol green (BCG), bromophenol blue (BPB) and bromothymol blue (BTB) has been developed. The method consists of extracting the yellow ion-pair formed into chloroform from aqueous medium. The ion-pairs have absorption maxima at 420, 410 and 415 nm with molar absorptivities of 3.64 × 10⁴, 3.12 × 10⁴ and 2.31 × 10⁴1 mol^–1 cm^–1 for BCG, BPB and BTB, respectively. The method obeys Beer's law over the concentration ranges 0.6–12.0, 0.12–8.8 and 1.2–11.3 ag/ml amprolium hydrochloride for BCG, BPB and BTB, respectively. The method is simple, precise (relative standard deviation 0.665–2.210%), accurate (recovery 97.8–100.8%) and easily applied for pharmaceutical quality assurance for amprolium hydrochloride in raw materials and in formulated veterinary soluble powder.     

Indirect flow-injection spectrophotometric determination of meloxicam, tenoxicam and piroxicam in pharmaceutical formulations.

A simple and sensitive indirect spectrophotometric method for the assay of meloxicam (MX), tenoxicam (TX) and piroxicam (PX) in pure and in pharmaceutical formulations by flow injection analysis (FIA) has been proposed. The method is based on the oxidation of these drugs by a known excess of N-bromosuccinimide (NBS) in an acidic medium, followed by a reaction of excess oxidant with chloranilic acid (CAA) to bleach its purple color. The absorbance values increased linearly with increasing concentrations of the drugs. Variables, such as the acidity, reagent concentrations, flow rate of reagents and other FI parameters were optimized to produce the most sensitive and reproducible results. The system obeyed Beer's low over concentration ranges of 10 - 160, 20 - 200 and 10 - 160 microg/ml for MX, TX and PX, respectively. The common excipients and additives did not interfere with their determinations. The method was successfully applied to the determinations of MX, TX and PX in various pharmaceutical preparations. The results obtained by the proposed method were found to be in good agreement with those found by the official HPLC methods.     

Four spectrophotometric methods for determination of nitrofurazone in pharmaceutical formulations

Four simple and sensitive visible spectrophotometric methods (A-D) for the determination of nitrofurazone in bulk samples and pharmaceutical formulations are described. They are based on the formation of colored species by treating either its reduction product with 3-methylbenzothiazolin-2-one hydrazone in the presence of ferric chloride (method A: _max 600 nm) or its hydrolysis product with thiobarbituric acid (method B: _max 520 nm, 440 nm) or barbituric acid (method C: _max 400 nm) or by oxidizing it with excess N-bromosuccinimide and determining the consumed NBS using metol-isonicotinic acid hydrazide (method D: _max 620 nm).     

Spectrophotometric determination of some pharmaceutically-important aminoquinoline antimalarials

A simple and rapid spectrophotometric method for the assay of amodiaquine hydrochloride, chloroquine phosphate and primequine phosphate is described. The method is based on the interaction of the drug with tetracyanoethylene to give a stable charge transfer complex. The spectra of the complex show maxima at 413, 415 and 415nm, respectively, with high apparent molar absorptivities. Beer's law is obeyed in the concentration ranges 2–12, 1–8 and 2–12 g ml^–1 of the three drugs studied. The proposed method is applied to the determination of these drugs in certain formulations and the results are favourably comparable to the official methods.     

Simultaneous Determination of Bifonazole and Benzyl Alcohol in Pharmaceutical Formulations by Reverse-Phase HPLC

A simple, precise and sensitive reverse-phase high performance liquid chromatographic (RP-HPLC) method has been developed for the quantitation of bifonazole, an imidazole antifungal, simultaneously with benzyl alcohol, used as preservative, in pharmaceutical formulations. Method employed Zorbax Eclipse XDB-C18 (250×4.6 mm i.d., 5 m) column, methanol - ammonium acetate (pH 2; 65 mM) (65:35, v/v, pH^* 3.6) as mobile phase with flow rate of 1 mL min^–1 and variable UV detection at 220 and 252 nm. The proposed method was validated by testing its linearity, selectivity, recovery, repeatability, LOD/LOQ values and it was successfully employed for the determination of bifonazole and benzyl alcohol in pharmaceutical cream-based formulations.     

Complexometric determination of thallium(III) in pure solution,alloys, and complexes using semicarbazide hydrochloride as a releasing agent

A simple and accurate complexometric method is proposed for the determination of Tl(III) using semicarbazide hydrochloride as a releasing agent. In the presence of diverse metal ions, thallium is complexed first with a known excess of EDTA, and the surplus EDTA is then titrated with standard zinc sulfate at pH 5.0–6.0 (hexamine) using xylenol orange indicator. An excess of 5% aqueous neutral solution of semicarbazide hydrochloride is then added and the released EDTA is titrated against standard zinc sulfate solution. The method works well in the range 2–50 mg of Tl(III) with relative errors < 0.5%, standard deviations 0.05mg and coefficient of variation 0.4%. The method is applied for the determination of thallium content in complexes and alloy compositions     

Rapid spectrofluorimetric determination of lisinopril in pharmaceutical tablets using sequential injection analysis

The present work reports for the first time a simple and rapid method for the spectrofluorimetric determination of lisinopril (LSP) in pharmaceutical formulations using sequential injection analysis (SIA). The method is based on reaction of LSP with o-phthalaldehyde (OPA) in the presence of 2-mercaptoethanol (borate buffer medium, pH=10.6). The emission of the derivative is monitored at 455 nm upon excitation at 346 nm. The various chemical and physical conditions that affected the reaction were studied. The calibration curve was linear in the range 0.3–10.0 mg L^–1 LSP, at a sampling rate of 60 injections h^–1. Consumption of OPA reagent was significantly reduced compared with conventional flow injection (FI) systems, because only 50 L of OPA was consumed per run. The method was found to be adequately precise (s_r=2% at 5 mg L^–1 LSP, n=10) and the 3 detection limit was 0.1 mg L^–1. The method was successfully applied to the analysis of two pharmaceutical formulations containing LSP. The results obtained were in good agreement with those obtained by use of high-performance liquid chromatography (HPLC), because the mean relative error, e_r, was <1.8%.     

High-Performance Liquid Chromatographic Method for the Determination of Nimesulide in Pharmaceutical Preparations

A simple, rapid, and precise high-performance liquid chromatographic method for the determination of nimesulide in pharmaceutical preparations was proposed using Ibuprofen as an internal standard. The separation was performed on a CLC C₁₈ (5 m, 25 cm × 4.6 mm i.d.) column with a mobile phase consisting of an acetonitrile–0.05 M KH₂PO₄ buffer mixture of pH 7.00 (55 : 45, v/v). The detection was carried out at 230 nm and the linearity range was found to be 0.5–100 g/mL. The method has been applied successfully to the determination of nimesulide in pharmaceutical formulations. The recovery values were found to be in the range of 99.23–100.13% with RSD values of less than 0.97%.     

Sequential Determination of Hydrocortisone and Epinephrine in Pharmaceutical Formulations via Photochemically Enhanced Fluorescence

The study describes a simple and sensitive method for the sequential determination of hydrocortisone (HDC) and epinephrine (EP) in pharmaceutical formulations. The intrinsic fluorescence of epinephrine was measured before submitting the sample to a photochemical reaction to form a fluorescent product from HDC or HDC esters (succinate and acetate). The sample treatment eliminated the fluorescence from EP, thus minimizing spectral interference on the HDC fluorescence. Limits of detection (3S_b/m) were estimated to be 40ngmL^–1 for HDC or HDC salts and 0.2ngmL^–1 for EP. Recovery experiments, made with commercial and laboratory simulated formulations, gave values between 96 and 103% for both HDC and EP. This method can be easily automated, e.g. via flow-injection techniques.