A spectrophotometric study of the determination of gold with phenothiazine

The reaction of Au(III) with phenothiazine has been studied and a reaction mechanism proposed. Optimal conditions for the reaction have been found and a new spectrophotometric method has been developed for determination of Au(III). The method is advantageous in its simplicity and reproducibility. Gold can be determined in the concentration range 2-20 mug/ml.     

A rapid spectrophotometric method for determination of piperazine

A spectrophotometric method has been developed for the determination of piperazine and its salts (citrate, phosphate, and tartrate) without prior separation, based on the interaction of piperazine or any of its salts with phenothiazine and N-bromosuccinimide in aqueous methanol. The products exhibit absorption maxima at 448, 595 and 645 nm. Measurements are made at 595 nm. Beer's law is obeyed in the concentration range 0.5-5 mug/ml for piperazine salts and 0.5-3 mug/ml for piperazine hexahydrate. The method is rapid, simple and successful for analysis of some pharmaceutical preparations.     

Spectrophotometric determination of cerium(IV) using a phenothiazine derivative.

A simple, rapid and sensitive spectrophotometric method has been proposed for the determination of cerium(IV) using a phenothiazine derivative, propionyl promazine phosphate (PPP). This method is based on the formation of a red-colored radical cation upon a reaction of PPP with cerium(IV) in a phosphoric acid medium having maximum absorbance at 513 nm. Beer's law is valid over the concentration range of 1-11 microg/ml with a Sandell's sensitivity value of 16.14 ng/cm2. The proposed method has been successfully applied to the analysis of magnesium-base cerium alloys and synthetic mixtures corresponding to various cerium alloys. Other phenothiazine derivatives viz. butaperazine dimaleate and propericiazine were also used for the determination of cerium(IV).     

Determination of clenbuterol in pharmaceutical preparations by reaction with o-phthalaldehyde using a flow-injection fluorimetric procedure

A new procedure for the determination of clenbuterol is proposed using flow-injection and fluorimetric detection. The method is based on the derivatization reaction of the primary amine group with o-phthalaldehyde in the presence of 2-mercaptoethanol. The calibration graph based on peak area was linear in the range 0.2-5 mug ml(-1) and the detection limit was 0.06 mug ml(-1). The method was validated using a reference spectrophotometric procedure and was applied to the determination of the drug in commercial pharmaceutical preparations.     

Spectrophotometric determination of gallium in alloys and fly-ash with pyridoxal derivatives of thiocarbohydrazide and carbohydrazide

The symmetric derivatives of pyridoxal with thiocarbohydrazide and carbohydrazide, and the asymmetric derivatives of pyridoxal and salicylaldehyde with the same hydrazides have been synthesized and their analytical potential for spectrophotometric and kinetic fluorimetric determination of metal ions was studied. Gallium(III) and PyMAU(1,3-bis{[4-(2-methyl-3-hydroxy-5-hydroxymethyl)pyridyl]methyleneaminourea at pH = 4.2 form a complex with a single absorption maximum at 425 nm, which can be extracted into cyclohexanone in the presence of a controlled amount of sodium perchlorate. The extract has maximum absorbance at 435 nm. Both systems can be used for determining gallium. The optimal range of gallium concentration for measurement in a 1-cm cell is 0.5-1.25 gmg/ml for the procedure in homogeneous medium ((425) = 3.76 x 10(4).mole(-1).cm(-1)) and 0.25-1.25 mug/ml for the extraction procedure ((435) = 5.30 x 10(4) 1.mole(-1).cm(-1). The latter procedure has been applied to the determination of gallium in alloys and fly-ash.     

Spectrophotometric methods for the determination of tamoxifen citrate

Three simple and sensitive spectrophotometric methods for the determination of tamoxifen citrate have been developed. They are based on the formation of an ion-association complex between the drug and a dye, Erioglaucine A, which is extractable into chloroform and has an absorption maximum at 625 nm (method A), oxidation with excess potassium permanganate and the determination of unconsumed permanganate using Fast Green FCF (method B), or by the formation of a coloured cobalt thiocyante coordination complex which is extracted into benzene and measured at 635 nm (method C). Beer's law limits for methods A, B, and C are 0.5-3.0 mug ml(-1), 1.0-6.0 mug ml(-1) and 100-500 mug ml(-1), respectively. No interference was observed from tableting additives and the applicability of the methods was examined by analysing tablets containing tamoxifen. The quantities determined were 99.0-100.03% of the exptected values.     

FI-on line photochemical reaction for direct chemiluminescence determination of photodegradated chloramphenicol

A new, simple, clean and selective flow injection strategy based on the tandem photochemical reaction-chemiluminescence detection was applied to the determination of chloramphenicol. The determination is based on the on-line photodegradation of the drug in a glycine buffer at pH 8.8 by using a photoreactor consisting of 697 cmx0.5 mm PTFE tubing helically coiled around an 8 W low-pressure mercury lamp. Photodegradated chloramphenicol is detected by direct chemiluminescence of resulting photo-fragments and their subsequent reaction with potassium permanganate in sulfuric acid medium as oxidant. The method allows the chemiluminescence determination of compounds which do not exhibit native chemiluminescence. The calibration graph was linear up to 14 mug ml(-1) chloramphenicol, the limit of detection was 30 ng ml(-1), the relative standard deviation was 2.4% for 7 mug ml(-1) of the drug and the sample throughput was 60 h(-1). Taking into account the importance of the medium of photodegradation on the mechanism of photodegradation a comparative study in terms of selective was performed for different chemical media employed in the procedure of photodegradation. The proposed method was applied to the determination of chloramphenicol in commercially available pharmaceutical formulations.     

Reversed-phase liquid chromatographic determination of isoniazide in human urine as a test of the genetically predetermined type of biotransformation by acetylation

A new method of determination of genetically predetermined type of biotransformation by acetylation rate using reversed-phase liquid chromatography (RP-HPLC) was described. The method is based on determination of isonicotinic hydrazide (INH) which is excreted with the patient's urine during 24 h period after oral administration of 0.4 g of the drug. INH is used as pharmacogenetic marker. Precolumn derivatization of 4-chloro-5,7-dinitrobenzofurazan is used at RP-HPLC determination of INH and a new drug phosphabenzide (diphenylphosphinylacetic hydrazide, DPPAH) with specrtophotometric detection in urine. The limit of INH detection was 0.27 mug ml(-1) and the one of DPPAH was 0.82 mug ml(-1). As a result of pharmacokinetic investigation it was discovered that bimodal distribution by acetylation rate for DPPAH is less apparent than in the case of INH. It is shown, that immunomodulator xymedone (N-(beta-oxyethyl)-4,6-dimethyldihydropirimidon-2) is the acetylation inductor of xenobiotics.     

Simultaneous flow-injection determination of chlorpromazine and promethazine by photochemical reaction

Chlorpromazine and promethazine were simultaneously determined by irradiating flow-injection manifolds with ultraviolet light. The simultaneous determination was based on the difference in pH of the media where the photochemical conversion of each phenothiazine into a fluorescent product took place. The choice of the best flow-injection configuration and mathematical treatment for solving the mixtures are discussed. Chlorpromazine and promethazine can be simultaneously determined at the mug/ml level with r.s.d. values between 2 and 4% and sampling frequencies in the range 30-40/hr.     

Fluorimetric determination of phenothiazine derivatives by photooxidation in a flow-injection system

Flow-injection analysis (FIA) was combined with photochemically induced fluorescence (PF) detection for the determination of four phenothiazine derivatives, including unsubstituted phenothiazine, thionine, Azure A and Methylene Blue. The working analytical parameters (flow-rate, injected volume, photoreactor length) were optimized. Linear calibration graphs were obtained over about two orders of magnitude, with relative standard deviation within the range 1-2.3%. Limits of detection were between 13 and 35 ng/ml, according to the compound. The FIA-PF method was applied to the determination of phenothiazines in urine samples. Mean recoveries ranged from 94 to 117%.     

The polarographic behaviour of ketoprofen and assay of its capsules using spectrophotometric and voltammetric methods

The quantitative determination of ketoprofen using spectrophotometric and voltammetric methods are described. The spectrophotometric procedure depends upon the reaction of ketoprofen with N-bromosuccinimide (NBS). The residual reagent is then determined by formation of violet colour with 2,2-diphenyl-l-picryl hydrazine (DPPH(2)). The consumed NBS would correspond to ketoprofen. Beer's law is valid over the concentration range 5-80 mug/ml of the drug. Direct current (DC) polarography allows to study the reduction behaviour of ketoprofen at the dropping mercury electrode (DME) using different supporting electrolytes at different pH values. Direct current stripping voltammetry (DCSV) was used for the quantitative measurements of the drug. The calibration graph of peak current vs concentration was linear from 0.254 x 10(-2) to 0.254 mug/ml. In model solutions as little as 5.08 x 10(-4) ng/ml ketoprofen can be detected by DCSV. Both methods were applied successfully for the determination of ketoprofen either in pure or dosage forms.     

Determination of phenothiazines by charge-transfer complex formation with chloranilic acid

A rapid and sensitive spectrophotometrc method has been developed for the microdetermination of some phenothiazine derivatives as the pure substances and in different dosage forms. The method depends on the formation of stable donor-acceptor complexes between phenothiazines and chloranilic acid in an acetonitrile-2-propanol solvent mixture. The resulting intensely purple chloranilic acid radical anion possesses a characteristic absorption maximum at 515 nm. Beer's law is obeyed over the concentration ranges 1-6, 1-10 and 5-30 mug ml for prochlorperazine dimaleate, trifluoperazine dihydrochloride and thiethylperazine dihydrochloride, with apparent molar absorptivities of 7.76 x 10(4), 1.95 x 10(4) and 6.64 x 10(3) 1. mole(-1).cm(-1), respectively. Statistical comparison of the results with those of an official method shows excellent agreement and indicates no significant difference in precision.     

Extractive spectrophotometric methods for the assay of sildenafil citrate (Viagra) in pure form and in pharmaceutical formulations

Two simple and sensitive extractive spectrophotometric methods for the determination of sildenafil citrate (SC) are proposed. The methods are based on the formation of ion-association complexes of sildenafil citrate with bromocresol green (BCG, method A) and with chromoxane cyanine R (CCR, method B) in aqueous acidic buffer. The complex species, extractable to chloroform phase, were quantitatively measured at 415 and 460 nm for methods A and B, respectively. Beer's law was obeyed in the SC concentration range 1.25-25 mug ml(-1) with a limit of detection 0.16 mug ml(-1) and 1.5-60 mug ml(-1) with a limit of detection 0.18 mug ml(-1), respectively, for methods A and B. The methods have been successfully applied to the analysis of bulk drug and its tablets. No interference was observed from common pharmaceutical adjuvants.     

Determination of total proteins: a study of reaction between quinones and proteins

A previous study was undertaken to test the reaction of several quinones (p-benzoquinone; 2,5-dichloro and 2,6-dichloro p-benzoquinone; tetrachloro-p-benzoquinone; tetrachloro-o-benzoquinone; 2,5-dichloro-3,6-dihydroxy-p-benzoquinone; benz[a]anthracene-7,12-dione) with bovine serum albumin (BSA). From this study, we have devised a spectrophotometric method for determination of total proteins. The quinone, tetrachloro-p-benzoquinone (p-chloranil), showed the best result. The product of reaction between proteins and p-chloranil absorbed at 360 nm and Beer's law was followed up to 200 mug ml(-1) of BSA. The product of reaction of BSA/p-chloranil was stable for 30 min, after that the absorbance increased 16% and kept stable for 24 h. The p-chloranil method showed a limit of detection (1.25 mug ml(-1)) lower than the biuret method (52.0 mug ml(-1)) or p-benzoquinone (PBQ) method (2.6-4.0 mug ml(-1)). The method was applied to spectrophotometric determination of total proteins in blood plasma; the results were compared with the biuret method that is widely used in clinical analysis.     

Chemiluminescence determination of some fluoroquinolone derivatives in pharmaceutical formulations and biological fluids using [Ru(bipy)(3)(2+)]-Ce(IV) system

A new chemiluminescence (CL) method using flow injection has been described for the rapid and sensitive determination of three fluoroquinolone derivatives, namely ofloxacin, norfloxacin and ciprofloxacin hydrochloride. The method is based on the CL reaction of the studied fluoroquinolones with tris(2,2'-bipyridyl)ruthenium(II) [Ru(bipy)(3)(2+)] and Ce(IV) in sulfuric acid medium. Under the optimum conditions, the CL intensity is proportional to the concentration of the drugs in solution over the range 0.05-7.0 mug ml(-1) for norfloxacin, 0.05-6.0 mug ml(-1) for ciprofloxacin hydrochloride and 0.003-0.7 mug ml(-1) for ofloxacin. The limits of detection (s/n=3) were 3.1x10(-8) M norfloxacin, 2.6x10(-8) M ciprofloxacin hydrochloride and 5.5x10(-9) M ofloxacin. The method was applied successfully to the determination of these compounds in dosage forms and biological fluids.     

Mixed micellar medium for the spectrophotometric determination of molybdenum in molybdenum/tungsten mixtures

Effects of cetyltrimethylammonium bromide (CTAB) and/or nonylphenoxypolyethoxyethanol (OP) on the absorption spectra of the complexes of molybdenum and tungsten with bromopyrogallol red (BPR) were studied. Based on these effects, a mixture of CTAB and OP was thus selected as a medium for the selective and sensitive determination of Mo in Mo/W binary mixtures. Under the optimum conditions, Beer's law was obeyed over the range 0.06-0.8 mug ml(-1) Mo with molar absorptivity being 1.3x10(5) l mol(-1) cm(-1) and detection limit 0.025 mug ml(-1). For 1.0 mug Mo, at least 20 mug W did not interfere in the determination of Mo with average recovery and relative standard deviation being 99.5% and <2%, respectively. The method developed maintained the features of simplicity and rapidity and, moreover, its selectivity and sensitivity enhanced greatly due to the use of CTAB/OP mixed micellar medium. When coupled with a compatible concentration method, the proposed method could be used for the determination of trace Mo in natural waters.     

Malachite green as a reagent for detection and spectrophotometric determination of chromium(VI)

A sensitive and inexpensive method of spectrophotometric determination of chromium(VI), based on the absorbance of its complex with malachite green and acetic acid at pH 2.5 is reported. The complex shows a molar absorptivity of 8 x 10(4) l.mole(-1) cm(-1) at 560 nm, using malachite green and acetic acid as reference solution. The effect of time, temperature, pH and reagent concentration is studied and optimum operating conditions are established. Beer's law is applicable in the concentration range 2.0-22.8 mug/ml chromium(VI). The resin beads act as a catalyst and as little as 1.6 mug of chromium(VI) is detected in the resin phase as compared to 4.1 mug in the solution phase. The standard deviation in the determinations is +/-0.40 mug/ml for a 10.35 mug/ml solution.     

Flow-injection chemiluminometric analysis of some benzamides by their sensitizing effect on the cerium-sulphite reaction

A simple, highly sensitive chemiluminescent method using flow injection is described for the determination of three substituted benzamides, namely: sulpiride, sultopride and tiapride. The method is based on the sensitizing effect of these drugs on the chemiluminometric oxidation of sulphite by cerium(IV). The different experimental parameters affecting the chemiluminescence intensity were carefully studied and incorporated into the procedure. The method permits the determination of 0.05-2.5 mug ml(-1) sulpiride, 0.01-2.5 mug ml(-1) sultopride hydrochloride and 0.01-1.5 mug ml(-1) tiapride hydrochloride with minimum detectability of 0.01 mug ml(-1). The method was applied to the determination of these benzamides in pharmaceutical preparations and biological fluids.     

Spectrofluorimetric determination of guanethidine sulphate, guanoxan sulphate and amiloride hydrochloride in tablets and in biological fluids using 9,10-phenanthraquinone

A highly sensitive spectrofluorimetric method for the determination of some drugs of the monosubstituted guanidine derivatives in laboratory made tablets, in spiked human serum and in urine samples is presented. The method is based on the reaction of guanethidine sulphate (I), guanoxan sulphate (II) and amiloride hydrochloride (III) with 9,10-phenanthraquinone (IV) to give highly fluorescent derivatives. The linearity ranges were found to be 0.06-0.96 mug/ml for (I) and (II) and 0.04-0.28 mug/ml for (III), with relative standard deviation less than 2%. Mean percentage recoveries for tablets were found to be 99.9 +/- 1.3, 100.5 +/- 1.1 and 100.0 +/- 1.6 for I, II and III, respectively. For I and III the results are highly correlated with the B.P. methods. Using the synchronous fluorimetry, differentiation between I and II was possible. Chloroform, dichloromethane and ethyl acetate have been used to extract I, II and III, respectively from serum and urine at basic pH, followed by applying the proposed fluorimetric method. Percentage recoveries were found to be 95.7-102.2%. The limit of detection is 0.04 mug/ml for I and II and 0.02 mug/ml for III.     

Katalytische bestimmung von silberspuren in wabetariger lösung und nach extraktion

The application of the catalysed oxidation of Bromopyrogallol Red by potassium per- sulphate for silver determination is discussed. In aqueous solution silver concentrations of 0.5- 1 mug/ml can be determined and 1- 13 ng/ml in the presence of 1, 10-phenanthroline as activator. In combination with solvent extraction, catalytic determination of the extracted silver is possible even in presence of 200 mug of iron(III), cobalt(II) and palladium(II). By means of an automatic variant of the simultaneous comparison method a more sensitive determination (0.2-20 ng/ml) was achieved.