Sensitive and rapid spectrophotometric methods for determination of anticancer drugs

Sensitive, rapid, and simple spectrophotometric methods were developed for determination of the anticancer drugs vinblastine sulfate (VBS) and vincristine sulfate (VCS), which belong to the class of vinca alkaloids. The first method is based on the reaction of VBS and VCS with diazotized dapsone, forming yellow azo products with absorption maxima at 430 nm. The colored species obey Beer's law in the concentration range of 0.5-24 microg/mL for VBS and 0.5-12 microg/mL for VCS. The second method describes the reaction of VBS and VCS with iron(III) and subsequent reaction with ferricyanide in hydrochloric acid medium to yield blue products with absorption maxima at 750 nm. The Beer's law range for this method is 0.1-4 microg/mL for VBS and 0.5-10 microg/mL for VCS. With both methods, colored species were stable for 1 h. The methods are simple and reproducible and are applied for determination of VBS and VCS in pharmaceutical formulations. Commonly encountered pharmaceuticals added as excipients do not interfere in the analysis and the results obtained in the analysis of dosage forms agree well with the labeled contents.     

Validated polarographic methods for the determination of certain antibacterial drugs.

Two simple, precise, inexpensive and sensitive voltammetric methods for the determination of lomefloxacin (LFX), sparfloxacin hydrochloride (SFX), gatifloxacin (GFX), and moxifloxacin (MFX) were developed. The present methods were first used to explore the adsorption behavior of the four investigated antibacterial agents at a hanging mercury dropping electrode (HMDE), by a direct method and secondly by a modification via their complexation with PdCl(2). For the direct method, drugs were accumulated on HMDE, and a well-defined reduction peak was obtained in Britton-Robinson buffer of pH 7 for LFX and SFX, and pH 6 for GFX and MFX. The adsorptive stripping response was evaluated as a function of some variables such as the scan rate, pH, accumulation time and potential. For the modified method, the adsorptive behavior of Pd(II)-4-quinolone complexes at the HMDE developed a strippining voltammetry peak at a more negative potential than that of the free Pd(II) ions (-1.05 V). The limits of detection (LOD) were 2 x 10(-8) M, while the limits of quantification (LOQ) were 6 x 10(-8) M for the investigated drugs. The methods were applied to the determination of LFX, SFX, GFX, and MFX in biological samples and pharmaceutical preparations, and also compared with the official reference methods. Complete validation of the proposed methods was also done.     

Development and validation of spectrophotometric methods for determination of some cephalosporin group antibiotic drugs

A simple and direct spectrophotometric method is developed for the determination of some cephalosporin group antibiotic drugs such as Loracarbef (Lora), Ceftazidime (Ceft), and Cefaclor (Cefa) in bulk and pharmaceutical formulations. The optimum conditions for the analysis of aqueous solutions of drugs are studied. Under the optimum conditions, the three drugs could be assayed in the concentration range 2–9 × 10⁻⁵, 2–6 × 10⁻⁵, and 3–9 × 10⁻⁵ M for Lora, Ceft and Cefa, respectively. Detection and quantification limits are calculated. The obtained results showed good recoveries of 100.4, 107.4, and 100.7% for Lora, Ceft, and Cefa, respectively. The results obtained are compared favorably with those given by literature methods.     

Application of promethazine hydrochloride as a chromogenic reagent for the spectrophotometric determination of certain sulphonamide drugs

Summary The oxidative coupling reaction of promethazine · HCl with primary aromatic amines was applied to the determination of seven pharmaceutical sulphonamides. A mixture of an acidic solution (3.5% acetic acid) of the sulphonamide and the chromogenic reagent was treated with hypochloriteion. The wavelength of maximum absorption is 610 nm, the molar absorptivities range from 1.57×10⁴ to 1.89×10⁴ l mole^–1 cm^–1 and Sandell sensitivities range from 0.00972 to 0.0136 g cm^–2. A linear correlation was found between absorbance at max and concentration. The procedures developed for bulk sulpha drugs and some of their pharmaceutical preparations are rapid, accurate, precise and comparable to the Bratton-Marshall procedure.     

Sensitive spectrophotometric methods for the determination of pindolol

Two simple, sensitive and reproducible visible spectrophotometric methods for the determination of Pindolol in amounts as low as 1 g are described. The first method is based on the oxidation of Pindolol by sodium nitrite under acidic conditions and the coupling of the oxidised intermediate withN-1-(naphthyl)ethylenediamine dihydrochloride (NED) to the colored product. The spectrum of the colored solution is strongly dependent on the length of the incubation period at room temperature during oxidation (3 min, _max 620 nm; 10 min or above _max 540 nm). Other couplers [diphenylamine (DPA) or 1-naphthylamine (-NA)] or indole derivatives (indole, tryptophan or isatin) when used instead of NED or Pindolol, respectively, also react to give a colored product with same maximum in each case irrespective of the length of the incubation period during oxidation. The second method is based on the coupling reaction involving Pindolol and 1,2-naphthaquinone-4-sulphonic acid sodium salt to form a coloured product (_max 660 nm). Both the methods have been employed to determine Pindolol content in bulk forms and pharmaceutical preparations.     

New spectrophotometric methods for the determination of rhenium

Recent spectrophotometric methods for the determination of rhenium are described and discussed.     

Batch and flow-injection methods for the spectrophotometric determination of olanzapine

An indirect batch spectrophotometric and direct flow-injection (FI) visible spectrophotometric methods have been developed for the determination of the novel anti-psychotic drug olanzapine (OLA). The batch method is based on the oxidation of olanzapine by a known excess of potassium hexacyanoferrate(III) in the presence of the mixture of sulphuric and phosphoric acids (1:1 (v/v)). The absorbance of unreacted oxidant is measured at 425 nm. The absorbance decreases linearly with increasing concentration of the assayed drug. The FI method with detection at 540 nm is based on the direct oxidation of olanzapine one of two oxidants, cerium(IV) sulphate or potassium hexacyanoferrate(III) in acidic medium. The calibration graph were linear over the range of 2.5-40 μg ml⁻¹ in the batch method and 0.05-300 and 0.5-250 μg ml⁻¹ in the FI methods, used cerium (IV) sulphate and potassium hexacyanoferrate (III) respectively. Both FI methods gave similar results in terms of precision and accuracy. The relative standard deviation (R.S.D.), was <1%. The accuracy, obtained from recovery experiments, was 97.9-99.4%. The batch method gave slightly higher R.S.D. values (up to 2.3%) and lower values of accuracy (the recovery was between 96.5 and 96.6%). The methods developed were applied to the determination of olanzapine in a pharmaceutical product.     

Kinetic and maximum-absorbance spectrophotometric methods for the determination of olanzapine

Two simple and sensitive spectrophotometric methods were developed for the determination of olanzapine (OLZ) based on its oxidation with potassium iodate in a sulfuric acid medium to produce an intense violet-colored species exhibiting a maximum absorbance at 537 nm. The initial rate of formation and the maximum absorbance of the violet-colored oxidized product were monitored, in the first and second methods. The various experimental parameters affecting the rate of development and stability of the oxidized product were carefully studied and optimized. Beer’s law was obeyed up to 4.0 and 7.0 μg cm⁻³ OLZ with correlation coefficients of 0.998 and 0.996 (n = 6) and detection limits of 0.1 and 0.15 μg cm⁻³, for the initial rate and maximum absorbance methods. The proposed methods were conveniently applied to the determination of OLZ in its dosage forms and in spiked serum samples. Correspondence: Ashraf A. Mohamed, Department of Chemistry, Faculty of Science, King Faisal University, P.O. Box 1759, Al-Hassa-31982, Saudi Arabia.     

Kinetic and maximum-absorbance spectrophotometric methods for the determination of olanzapine

Two simple and sensitive spectrophotometric methods were developed for the determination of olanzapine (OLZ) based on its oxidation with potassium iodate in a sulfuric acid medium to produce an intense violet-colored species exhibiting a maximum absorbance at 537 nm. The initial rate of formation and the maximum absorbance of the violet-colored oxidized product were monitored, in the first and second methods. The various experimental parameters affecting the rate of development and stability of the oxidized product were carefully studied and optimized. Beer’s law was obeyed up to 4.0 and 7.0 μg cm⁻³ OLZ with correlation coefficients of 0.998 and 0.996 (n = 6) and detection limits of 0.1 and 0.15 μg cm⁻³, for the initial rate and maximum absorbance methods. The proposed methods were conveniently applied to the determination of OLZ in its dosage forms and in spiked serum samples.     

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).     

Extractive spectrophotometric methods for determination of zolmitriptan in tablets

Two simple and sensitive extractive spectrophotometric methods have been developed for determination of zolmitriptan (ZTP) in tablets. These methods are based on the formation of yellow ion-pair complexes between ZTP and tropaeolin OO (TPOO) and bromothymol blue (BTB) in citrate-phosphate buffer of pH 4.0 and 6.0, respectively. The formed complexes were extracted with dichloromethane and measured at 411.5 and 410 nm for TPOO and BTB, respectively. The best conditions of the reactions were studied and optimized. Beer's law was obeyed in the concentration ranges of 2-20 and 1.5-17 microg/mL with molar absorptivities of 1.42 x 10(4) and 1.60 x 10(4) L/mol/cm for the TPOO and BTB methods, respectively. Correlation coefficients were 0.9998 and 0.9999 for TPOO and BTB methods, respectively. Limits of detection of the TPOO and BTB methods were 0.341 and 0.344 microg/mL, respectively, and the limits of quantitation were 1.034 and 1.051 microg/mL, respectively. Sandell's sensitivity and stability constant were also calculated. The proposed methods have been applied successfully for the analysis of the drug in its dosage forms. No interference was observed from excipients present in tablets. Statistical comparison of the results with those obtained by a high-performance liquid chromatography method showed excellent agreement and indicated no significant differences in accuracy and precision.     

Some azo-dye reagents for the spectrophotometric determination of cadmium

2-[2-(5-Bromopyridyl)azol-4,5-dimethylphenol (BrPDMP) and 2-[2-benzothiazolylazo)-5-dimethylaminophenol (BTADAP) have been synthesised and compared, as reagents for cadmium, with the related dyes BrPADAP and BTDMP. The new dyes both form stable highly coloured 2:1 complexes with cadmium, with molar absorptivities (in o-xylene solution) of 3.8 x 10(4) 1.mole(-1).cm(-1) at 590 nm (BrPDMP) and 4.5 x 10(4) 1.mole(-1).cm(-1) at 600 nm (BTADAP). Cadmium can be determined by extraction under alkaline conditions with a solution of BTADAP in xylene. Beer's law is obeyed up to at least 16 mug of cadmium. A limit of detection of 0.15 mug has been estimated and a coefficient of variation of 3.3% at the 5 mug level was found. The only species which interfere seriously are Co(2+), Ni(2+), and Ca(2+). A 200-fold excess of zinc may be tolerated. The method has been applied to the determination of cadmium in water samples, plant materials and hair. Interferences were overcome by preliminary extraction into Aliquat/carbon tetrachloride. The acid dissociation constant of BTADAP (pK = 9.5) and formation constant of the cadmium-BTADAP complex (log beta = 15.1) have been determined.     

Studies on spectrophotometric methods of thallium determination

Eight sensitive methods of spectrophotometric determination of thallium have been studied and compared experimentally. The comparative criteria were: molar absorptivity, colour contrast of the basic reaction, working concentration interval and practical determination limit for thallium, precision of the method (the standard deviation), and selectivity. According to these criteria the best methods of extraction-spectrophotometric determination of thallium are those using Brilliant Green, Crystal Violet, Methyl Violet and Rhodamine B. The sensitivity depends very much on the oxidant used for conversion of Tl(I) into Tl(III). The oxidants suitable for each of the recommended methods are discussed.     

New spectrophotometric methods for determination of captopril bulk drug and tablets

Three simple, rapid and sensitive methods for the assay of captopril which is an effective alternative to digitalis were developed. These methods are based on the oxidation reaction in aqueous solution of captopril with either ferric chloride or iodine. The indirect quantitation of the product was carried out at 523, 351 and 620 nm for ferro-bipyridyl, residual iodine and residual iodine-starch complex, respectively. All variables were studied to optimize the reaction conditions. Regression analysis of Beer's plot showed good correlation in a general concentration range of 0.25-25 mug captopril/ml. No interference was observed from hydrochlorothiazide diuretic which was recently introduced in combination with captopril or other common pharmaceutical adjuvants. The validity of the methods was tested by analysing capoten and capozide tablets. Recoveries were 99.1-102.8%.     

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).     

Kinetic spectrophotometric determination of certain cephalosporins using oxidized quercetin reagent

A simple, precise and accurate kinetic spectrophotometric method for determination of cefoperazone sodium, cefazolin sodium and ceftriaxone sodium in bulk and in pharmaceutical formulations has been developed. The method is based upon a kinetic investigation of the reaction of the drug with oxidized quercetin reagent at room temperature for a fixed time of 30 min. The decrease in absorbance after the addition of the drug was measured at 510 nm. The absorbance concentration plot was rectilinear over the range 80–400 μg mL⁻¹ for all studied drugs. The concentration of the studied drugs was calculated using the corresponding calibration equation for the fixed time method. The determination of the studied drugs by initial rate, variable time and rate-constant methods was feasible with the calibration equations obtained but the fixed time method has been found to be more applicable. The analytical performance of the method, in terms of accuracy and precision, was statistically validated; the results were satisfactory. The method has been successfully applied to the determination of the studied drugs in commercial pharmaceutical formulations. Statistical comparison of the results with a well established reported method showed excellent agreement and proved that there is no significant difference in the accuracy and precision.     

Oxidative coupling for the spectrophotometric determination of certain cephalosporins and acetaminophen in drug formulations

A spectrophotometric method for the determination of some cephalosporins and acetaminophen is described. The method is based on the hydrolysis of the cephalosporin in sodium hydroxide solution to produce the sulphide ion and the conversion of the sulphide with the p-phenylenediamine to form a violet colour. Acetaminophen is hydrolysed in sulphuric solution and the resulting p-aminophenol is oxidized with sulphide ion in the presence of iron(III) to form a red product. The method has been successfully applied to the assay of some cephalosporins and acetaminophen in drug formulations.     

Spectrophotometric methods for the determination of osmium-I Extraction and ultraviolet spectrophotometric determination of osmium tetroxide

An ultraviolet spectrophotometric method is presented for the détermination of milligram quantities of osmium in solutions of uranyl sulphate. Osmium is first oxidised to the octovalent state and the osmium tetroxide which is formed, is selectively extracted with chloroform. The ultraviolet absorption spectrum'of osmium tetroxide in chloroform has a series of absorption bands with peak absorbancies at 282, 289, 297, 304 and 312 mμ and molar absorbancy indexes of 1870, 1760,1640, 1400 and 1000, respectively. For each wavelength, the optimum concentration range for the determination of osmium was evaluated. From 0.4 to 3.3 mg of osmium can be determined with a coefficient of variation of 3%. Of the elements tested only chloride and octovalent ruthenium interfere; however, both of these interferences can be eliminated.     

Selective spectrophotometric determination of ascorbic acid in drugs and foods

A new analytical method was developed for the determination of ascorbic acid. The method is based on the reaction of ascorbic acid with 4-chloro-7-nitrobenzofurazane (NBD-Cl) in the presence of 0.2M sodium hydroxide, where a bluish green colour (lambda(max) 582 nm) is developed after dilution with 50% (v/v) aqueous acetone solution. Beer's law was obeyed in a concentration range of 5-20 microg ascorbic acid/ml with a good correlation coefficient (r = 0.9990). The method was found to be highly specific for the determination of ascorbic acid in the presence of dehydro-ascorbic acid, all other vitamins and minerals possibly present in multivitamin preparations, rutin, salicylamide, acetyl salicylic acid, paracetamol, caffeine, phenylephrine hydrochloride and dipyrone. Moreover, the proposed procedure was also successfully applied for the determination of ascorbic acid in some canned and fresh fruit juices, some vegetables and infant milk products without interference from coloured and other substances present in the plant extracts.     

Indirect spectrophotometric and atomic absorption spectrometric methods for the determination of potassium

Summary Indirect spectrophotometric and atomic absorption spectrometric methods for the determination of traces of potassium are proposed which are based on the precipitation of potassium tetraphenylborate and the determination of excess reagent in the supernate. The tetraphenylborate forms the tetraphenylborato-bis-(2,9-dimethyl-1,10-phenanthroline)copper(I)-complex which is extracted with ethyl acetate. Either the absorbance of colored extract is measured spectrophotometrically at 456 nm, or the copper in the extract is measured by atomic absorption spectrometry using the 324.7 resonance line.

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Zusammenfassung Methoden der Spektrophotometrie und der Atomarabsorption für die Kaliumbestimmung wurden vorgesehlagen, die auf der Fällung von Kaliumtetraphenylborat und der Bestimmung des Reagensuberschusses beruhen. Dabei bildet sich ein Tetraphenylborato-bis(2,9-dimethyl-1,10-phenanthrolin)-Kupfer(I)-Komplex, der mit Essigester extrahiert wird. Entweder wird dann die Farbe des Extraktes spektrophotometrisch bei 456 nm oder das Kupfer durch Atomarabsorptionsmessung mit Hilfe der Resonanzlinie 324,7 bestimmt.