Utility of Derivative Spectrophotometry in the Determination of Carbochromen Hydrochloride and Dipyridamole in the Presence of Their Oxidative Degradation Products

Abstract

Direct spectrophotometric methods for the determination of carbochromen hydrochloride and dipyridamole, each in the presence of its oxidative degradation products, are presented. the methods are based on the first derivative (D₁) and second derivative (D₂) spectrophotometric measurement (absolute trough, U) at 336 nm and (Peak-trough, Y) at 309–342 nm for carbochromen hydrochloride and at 240–260 nm(U) and 246–268 nm(Y) for dipyridamole. Plots of D₁ or D₂ versus concentration were linear over the concentration range of 8.00–16.00 μg/ml for carbochromen hydrochloride and 4.00–12.00 μg/ml for dipyridamole. Oxidative degradation of these drugs has been optimized with respect to hydrogen peroxide concentration. Determining the intact in coexistence with its oxidative degradation product, the proposed derivative spectrophotometric methods proved to be of high potential in correcting the systematic error appearing in the results of the A_max method due to the latter. Assaying the commercial tablets, the proposed method gave results of high accuracy and reproducibility.     

A Stability-Indicating Hplc Analysis of Famotidine and Its Application to Kinetic Studies

Abstract

A stability-indicating HPLC analytical method has been developed for the determination of the H₂-receptor antagonist, famotidine in the presence of its degradation products. the method utilizes reversed phase chromatography with UV detection and internal calibration techniques. the mobile phase was comprised of 84% ammonium acetate buffer (pH 2.9) and 16% acetonitrile and pumped at a flow rate of 1.5 ml/min. Quantitation was performed by measuring the peak height ratio of drug to internal standard (salicylic acid). the limit of famotidine detection was determined to be 10 ng (0.4 ug/ml) with a signal to noise ratio of 3:1. Within day coefficient of variation of the method was 2.22% (2.5 μg/ml) and 0.82% (10 μg/ml). Between day coefficient of variation based on the slopes of daily prepared standard curves was 4.70%. the developed method was used to determine the drug content of famotidine tablets. Further, it was used to investigate the kinetics of degradation of the drug in an acidic solution.     

Stability Indicating HPLC Analysis of Dibromodulcitol in Aqueous Solutions

Abstract

A stability-indicating HPLC analytical method for the anticancer agent dibromodulcitol (DBD, Mitolactol, NSC-104800) has been developed that will completely resolve the compound from its degradation products. A 5 μm octadecylsilane analytical column was used in conjunction with a refractive index detector, with a mobile phase of 98:2 water/methanol. The limit of DBD detection was determined to be 250 ng (5 μg/ml) with a signal to noise ratio of 2:1. Intraday variation of the method, as percent relative standard deviation, was 4.37% (12.5 μg/ml) and 0.973% (250 μg/ml), and interday variation was 3.93% (250 μg/ml). Comparison with potentiometric titration of bromide after digestion of DBD with NaOH indicated that the method was more sensitive and specific than titration. The method has been used in tablet content analysis, as well as degradation studies of DBD in solution.     

Simultaneous Determination of Micro Bromide and Iodide by Kinetic Spectrophotometric Method

ABSTRACT

ABSTRACTA new kinetic spectrophotometric method for the simultaneous determination of concentrations of micro bromide and iodide has been proposed. It is based on their catalytic effects on the reaction of m-cresol purple oxidized by potassium periodate in hydrochloride acid medium. The reaction rate was monitored by measuring the decrease in absorbance at 528nm and the increase in absorbance at 455nm. The total difference in absorbance of the sum of bromide and iodide is identical with determination of bromide was carried out after Cr(VI) oxidized I? to I₂, and I₂ was removed by extraction with CCI₄, and the amount of iodide was measured by subtracting the absorbance change of bromide from the total absorbance change in the presence of bromine and iodide. The optimum conditions influencing the reaction rate were studied. The linear range of determination is 0～4.0μg/ml for Br? and 0～3.0 μg/ml for I?. The detection limits are 0.032μg/ml for Br? and 0.059 μ/ml for I?. The method was successfully applied to the determination of micro amounts of bromide and iodide in food and life samples.     

Simultaneous Quantitation of Minoxidil and Tretinoin in Magistral and Pharmaceutical Preparations by First Derivative Spectrophotometry

Abstract

A first derivative spectrophotometry method has been developed for the simultaneous quantitation of minoxidil and tretinoin. The method is based on measuring the first derivative signals (D₁) of minoxidil and tretinoin at 290 and 351 nm, respectively, without any interference from each other, or any other coexisting materials. Beer's law was valid over the concentration range 2–10 μg/ml of minoxidil and 0.25–1.25 μg/ml of tretinoin. The proposed method has been applied successfully to the determination of some magistral and pharmaceutical preparations. Relative standard deviations for the assay of both drugs were less than 0.95%.     

Determination of Formaldehyde in Waste Water by Lucigenin Chemilummescence

Abstract

A chemiluminescence analysis has been developed for the determination of formaldehyde based on its inhibition of the chemiluminescence reaction of lucigenin-C10^?-H₂o₂. The method is sensitive, convenient and selective with a detection limit of 0.05ng/ml. The linear dynamic range is 1.0ng/ml to 0.1 μg/ml. The variation coefficient of ten determinations for 2.Ong/ml formaldehyde is 1.2%. Applications to the trace determination of formaldehyde in industrial waste waters are discussed.     

A Fluorimetric Method for the Determination of Atmospheric Sulphur Dioxide With 2′, 7′—Dichlorofluorescein∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of atmospheric sulphur dioxide with dichlorofluorescein as fluorogenic reagent (λ_ex = 505 nm, λ_em = 520 nm) at pH 4.0–6.0. A linear calibration curve was obtained in the range 0.01–0.40 μg SO₂/25 ml. The detection limit is 0.01 μg SO₂/25 ml. Nitrogen dioxide does not interfere with the method. The method was successfully applied to the determination of atmospheric sulphur dioxide.

     

A High Performance Liquid Chromatography Method for the Determination of Ranitidine in Plasma

Abstract

Ranitidine hydrochloride is a highly potent H₂ receptor antagonist of value in the treatment of peptic ulceration. A method is described for the determination of ranitidine in biological fluids. The drug is extracted from plasma prior to determination by reverse phase high performance liquid chromatography. The method is sensitive enough to determine 10ng ranitidine per ml in plasma. The h.p.l.c. method has been automated so that analysis can be carried out without attention over a 24 hour period. The automated h.p.l.c. method has been used for studying the pharmacokinetics of oral and intravenous doses of ranitidine hydrochloride administered to man.     

Kinetic Flow Injection Spectrophotometric Determination of Nitrite by its Catalytic Effect on the Oxidation of Chlorophosphonazo-pN by Bromate

Abstract

A flow injection kinetic method has been developed for the determination of nitrite, based on its catalytic effect on bromate oxidation of chlorophosphonazo-pN in H₂SO₄ medium. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance at 551 nm. The sampling frequency was 83 h^?1. The calibration curve was linear between 0.050 and 1.00 μg/ml, and the detection limit was 0.018 μg/ml. The proposed method was applied to the determination of nitrite in waters and soil with satisfactory results.     

High-Performance Liquid Chromatographic Determination of Acetazolamide in Human Plasma

Abstract

A simple, rapid and specific HPLC method has been developed to determine acetazolamide concentrations in human plasma. The assay procedure requires only 250 μl of sample with direct injection of the organic supernatant after protein precipitation with acetonitrile. Chlorothiazide was used as an internal standard. A reversed-phase C₁₈ μBondapak column was employed for the chromatographic separation. The eluent was monitored at 265 nm using a UV variable wavelength detector. The retention times for acetazolamide (ACZ) and chlorothiazide (CTZ) were 6 and 8 min respectively. A linear relationship (r).995) was obtained over the 1-20 μg/ml concentration range. The limit of sensitivity for ACZ was 0.5 μg/ml, with greater than 85% recovery of ACZ and internal standard. The method was applied to human plasma samples obtained after administration of a 250 mg acetazolamide tablet.     

A Fluorimetric Method for the Determination of Cyanide with Fluorescein and Iodine∗

Abstract

A rapid, simple and sensitive fluorimetric method has been developed for the determination of cyanide with fluorescein as fluorogenic reagent (λ_ex = 494 nm, λ_em = 514 nm) at pH 6.0–7.0. A linear calibration curve was obtained in the range 0.004–2.0 μg CN^?/25 ml. The detection limit is 0.004 μg CN^-/25 ml. The method was successfully applied to the determination of cyanide in waste water.

     

Flow Injection Chemiluminescence Determination of Difenidol Hydrochloride Using N-Chlorosuccinimide-Dichlorofluorescein Reaction

Abstract

A flow injection method combined with chemiluminescence detection was described for the determination of difenidol hydrochloride. Strong chemiluminescence was recorded when difenidol hydrochloride was added into the reaction mixture of N-chlorosuccinimide with dichlorofluorescein in alkaline medium. The experimental conditions that affected the chemiluminescence signal, including the concentrations of reactants, the reaction medium, and the instrumental parameters, were carefully optimized. Under the optimum experimental conditions, the enhanced chemiluminescence intensity was linear related to the concentration of difenidol hydrochloride in the range of 4.0 × 10^?9 to 4.0 × 10^?7 g/ml. The detection limit for difenidol hydrochloride was 7 × 10^?10 g/ml, and the sample throughput was 90/h. The relative standard deviation was 2.5% for 5.0 × 10^?8 g/ml difenidol hydrochloride solution (n = 11). The interference of common inorganic ions, excipients, and additives used in pharmaceutical preparation was studied, which showed the method has higher tolerance limit for these substances and has good selectivity. As a preliminary application, the method was applied to the determination of difenidol hydrochloride in tablets, and the satisfactory results were achieved.     

Simultaneous Analysis of Pyridoxine and Melatonin in Tablet Formulation by Derivative Ultraviolet Spectroscopy

Abstract

A method for simultaneous analysis of pyridoxine and melatonin by second and third derivative UV - spectroscopy, the “zero - crossing” technique, is described. The determination has been carried out in 0.1 mol dm^?3 hydrochloric acid solution and the concentration range of 2 – 10 μg/ml pyridoxine and 0.5 – 3.5 μg/ml melatonin. Lower limits of detection at the 95% confidence level were 0.26 μg/ml for pyridoxine and 0.05μg/ml for melatonin The advantages of the proposed method include its application for the assay and in-vitro dissolution studies of pyridoxine and melatonin from two different tablet formulations.     

Spectrophotometric Determination of Trimethoprim in Pure Form and in Pharmaceutical Preparations using Bromothymol Blue,Bromocresol Green and Alizarin Red S

ABSTRACT

Simple, sensitive and selective methods for the determination of trimethoprim (TMP) in pure form and in pharmaceutical formulations are described. The methods are based on the reaction of TMP as a π-electron donor with bromothymol blue (BTB), bromocresol green (BCG) and alizarin red S (ARS) as electron acceptors. The coloured products are quantified spectrophotometrically at their corresponding λ_max.

Beer's law is obeyed in case of BTB in the range 2.9-23.2 μg/ml (CHCl₃), 2.9-20.0 μg/ml (CH₂Cl₂) and 5.0-29.0 μg/ml (ClC₆H₅), in the case of BCG 2.9-27.5 μg/ml (H₂O/alc.), 2.9-18.3 μg/ml (CHCl₃) and 2.9-20.3 μg/ml (CH₂Cl₂) and for ARS in the range 3.0-12.0 μg/ml in H₂O/alc medium.

The specific absorptivities, molar absorptivities, Sandell sensitivities, standard deviations and percent recoveries are evaluated. Application of the suggested methods to dosage forms is presented and compared with the pharmacopoeial method. The interference from additives and sulfa compounds, especially sulfamethoxazole, has been overcome by extraction into chloroform or methylene chloride.     

Reversed-Phase High Performance Liquid Chromatographic and Thin Layer Chromatographic Methods for the Simultaneous Determination of Benazepril Hydrochloride and Hydrochlorothiazide in Cibadrex Tablets

ABSTRACT

Two procedures were developed for simultaneous determination of benazepril hydrochloride (I) and hydrochlorothiazide (II) in pure, laboratory made mixtures and in pharmaceutical dosage form “Cibadrex tablets® using reversed phase high performance liquid chromatographic and thin layer chromatographic methods.

For reversed phase HPLC, a new very sensitive, rapid, selective method was developed. The linearity ranges were 32-448 ng/20 μl and 40-560 ng/20 μl for benazepril hydrochloride and hydrochlorothiazide, respectively. The corresponding recoveries were 99.38 ± 1.526 and 99.2 ± 1.123.

The minimum detection limits were 7 ng/20 μl and 14 ng/20 μl for benazepril hydrochloride and hydrochlorothiazide respectively.

On the other hand, a new, simple, sensitive and fast thin layer chromatographic scanning densitometric method was developed for simultaneous determination of benazepril hydrochloride and hydrochlorothiazide using ethyl acetate: methanol: ammonia (85: 20: 10 v/v) as the developing system. The R_f values were 0.33 & 0.68 for benazepril hydrochloride and hydrochlorothiazide respectively. The minimum detection limit obtained was 0.12 μg/spot for benazepril hydrochloride and 0.24 μg/spot for hydrochlorothiazide. The mean percentage recoveries were 100.04 ± 1.102 and 99.31 ± 1.009 for benazepril hydrochloride and hydrochlorothiazide respectively.

The two proposed methods were simple, precise, sensitive and could be successfully applied for the determination of pure, laboratory made mixtures and pharmaceutical dosage forms. The results obtained were compared with those obtained by A ^1%.     

Spectrophotometric Determination of Tetracyclines in Pure Form and in Pharmaceutical Preparations,by a Molybdenum Blue Method

Abstract

A new and sensitive spectrophotometric method has been developed for the determination of tetracyclines either in a pure form or in Pharmaceuticals, by a molybdenum blue method. The procedure is based on the observation that, in sulphuric acid medium, tetracyclines reduce ammonium molybdate to molybdenum blue, the absorbance of which is proportional to the amount of antibiotic present. The variables affecting development of the color have been investigated and the conditions optimized. Beer's law is obeyed for up to 20 μg/ml of tetracycline HCl and oxytetracycline HCl, 28 μg/ml of demeclocycline HCl, 18 μg/ml of chlortetracycline HCl, 32 μg/ml of doxycycline HCl and 40 μ/ml of rolitetracycline. Molar absorptivities (1 mol^?1 cm^?1) and Sandell's sensitivities (μ cm^?2 per 0.001 absorbance unit) are, respectively: tetracycline HCl 4.9×10⁴ and 0.0098, oxytetracycline HCl 5.4×10⁴ and 0.0092, demeclocycline HCl 1.6×10⁴ and 0.0313, chlortetracycline HCl 5.5×10⁴ and 0.0094, doxycycline HCl 3.4×10⁴ and 0.0141, rolitetracycline 2.7×10⁴ and 0.0195.     

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.     

High-Performance Liquid Chromatographic Determination of SAZ-VII-23, A Novel Antiarrhythmic Agent,in Dog Plasma and Urine

Abstract

A HPLC method has been developed to determine the concentrations of SAZ-VII-23 (3-benzoyl-7-isopropyl-3,7-diazabicyclo[3.3.1]nonane HClO₄), a novel antiarrhythmic agent, in dog plasma and urine. Plasma treated with acetonitrile and alkalinized urine were extracted with chloroform- propanol (9:1). An aliquot was injected on to HPLC system using a C₆ reversed-phase column and acetonitrile-methanol-37.5 mM phosphate buffer, pH 6.8 (28.5:28.5:43 v/v) containing 4.0 mM triethylamine as mobile phase. Detection wavelength was 255 nm. The linear range were 0.04–8 μg/ml, and the lower limit of quantitation was 0.04 μg/ml in plasma and urine, respectively. The method was applied to determine plasma and urine concentrations and preliminary pharmacokinetic profiles of SAZ-VII-23 in a dog.     

Determination of Diketopiperazine in Soft Drinks by High Performance Liquid Chromatography

Abstract

Analytical method of diketopiperazine (5-Benzyl-3, 6-dioxo 2 piperazineacetic Acid: DKP), a major degradation product of aspartame (AMP), in soft drinks was developed by means of high performance liquid chromatography (HPLC). A sample was purified using Bond Elut SCX connected to Bond Elut C8 with 20% acetonitrile as the eluent. A Nucleosil 5-C₁₈ column was employed for the HPLC with 10 mM potassium dihydrogenphosphate and acetonitrile (85+15, v/v) adjusted pH to 4.0 as the mobile phase. The calibration curve was rectilinear in the range of 0.5 to 10.0 μg/ml for DKP. The average recoveries were 99.8% and 96.0% for DKP added to soft drinks at the level of 10 μ g/ml and 2.5 μ g/ml, respectively. The DKP was found in six commercial samples in the range of 9.5 to 26.0 μ g/ml.     

Sensitive Spectrophotometric Determination of Some Dibenzazepine Drugs with Diazotized P-Phenylenediamine Dihydrochloride

ABSTRACT

A simple, sensitive and selective spectrophotometric procedure was developed for the determination of imipramine hydrochloride, desipramine hydrochloride, clomipramine hydrochloride and trimipramine maleate belonging to dibenzazepine class of drugs. The method is based on the interaction of diazotized p-phenylenediamine dihydrochloride with the drug in sulphuric acid medium. The resulting chromophore was measured at 565 nm, and was stable for about 2.5 hr. The commonly encountered excipients and additives do not interfere with the determination. Dibenzazepine drugs can be determined in the range of 0.1-4.0 μg/ml, with a relative standard deviation of 1.92% for ten replicate measurement of 2.0 μg/ml dibenzazepine drugs. Results from the analysis of preformulations and commercial tablets by this procedure agree well with those of the official method.