Colorimetric determination of some sulphonamides with phenothiazine

Two simple and sensitive calorimetric procedures for determination of some sulphonamides with phenothiazine (thiodiphenylamine) are presented. One is based on reaction in aqueous alcohol solution in presence of hypochlorite, with direct measurement at 515 nm. The other is based on reaction in presence of copper(II) acetate at 70 degrees , extraction with chloroform and measurement at 515 nm. The method is applied to the determination of sulphonamides in pure and tablet form, with a coefficient of variation less than 2%.     

Stability-Indicating Method For The Determination Of N-Desmethyldiazepam And Simultaneous Determination Of Its Degradation Products

Abstract

A simple, direct and sensitive spectrophotometric method for the determination of the intact N-desmethyldiazepam in the presence of its degradation products, 2-amino-5-chlorobenzophenone and glycine, is developed. The proposed procedure is based on direct measurement of the absorbance of its acidified methanolic solution at 361 nm. The procedure determines 8–56 mcg ml^?1 of N-desmethyldiazepam with an accuracy of 100.2 ± 0.51%. The proposed procedure retains its accuracy in presence of up to 80% of the different degradation products. The procedure is applied successfully for the determination of N-desmethyldiazepam in bulk powder, tablets and drops.

Simultaneous determination of the different degradation products in the presence of the parent drug is also described. Thus, 2-amino-5-chlorobenzophenone is determined by direct measurement of its methanolic solution at about 380 nm, with an accuracy of 100.4 ± 0.42%. Glycine is determined colorimetrically using ninhydrin reagent in presence of pyridine, with an accuracy of 99.5 ± 0.78%.     

Screening method for organic aciduria by spectrofluorometric measurement of total dicarboxylic acids in human urine based on intramolecular excimer-forming fluorescence derivatization

A simple screening method of organic aciduria by spectrofluorometric measurement of total dicarboxylic acids in human urine is described. This method is based on an intramolecular excimer-forming fluorescence derivatization with a pyrene reagent, 4-(1-pyrene)butanoic acid hydrazide (PBH). Dicarboxylic acids in urine were converted to the corresponding dipyrene-labeled derivatives by reaction with PBH in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and pyridine, and the derivatives afforded intramolecular excimer fluorescence (420-540 nm) which can clearly be discriminated from the normal fluorescence (360-420 nm) emitted from reagent blanks. The technique is so selective that it permits spectrofluorometric measurement of total amount of dicarboxylic acids by the direct derivatization of diluted urine samples. The same reaction mixture has also served as a liquid chromatographic (LC) sample for the separative determination of individual dicarboxylic acids. The spectrofluorometric data did not contradict with the LC data. These methods were usefully applied to preliminary screening test of glutaric aciduria. In conclusion, the present derivatization method allows rapid and direct determination of total amount of dicarboxylic acids in human urine samples.     

Copper(II)-neocuproine as colour reagent for some biologically active thiols: Spectrophotometric determination of cysteine,penicillamine, glutathione,and 6-mercaptopurine

A new direct spectrophotometric method is described for determination of g/ml concentrations of four biologically important thiols: cysteine, penicillamine, glutathione, and 6-mercaptopurine. The method is based on reaction with copper(II)-neocuproine and subsequent measurement of the Cu(I)-neocuproine produced, at 458 nm. The method has been successfully applied to analysis for these thiols, with a relative standard deviation not exceeding 0.6%.     

7-(1-苯偶氮)-8-羟基喹啉-5-磺酸-曲拉通X-100双波长分光光度法测定微量铟

研究了７－（１－苯偶氮）－８－羟基喹啉－５－磺酸与铟的显色反应及分析应用,在曲拉通Ｘ－１００存在下,于ｐＨ４．５的ＮａＡｃ－ＨＡｃ缓冲介质中,铟与题示试剂形成组成比为１∶３的黄色配合物,最大吸收波长为４４０ｎｍ,表观摩尔吸光系数为３．８６×１０４Ｌ·ｍｏｌ－１·ｃｍ－１,同时在５５０ｎｍ呈现负峰,用双峰双波长法测定铟的表观摩尔吸光系数为７．３３×１０４Ｌ·ｍｏｌ－１·ｃｍ－１,灵敏度为单波长法的１．９倍,线性范围为０～０．６ｍｇ／Ｌ,该法用于硫硒化锌基陶瓷颜料及镀膜玻璃中铟的测定,结果满意。     

Spectrophotometric determination of acrivastine in urine and capsules

Three sensitive and accurate spectrophotometric methods are presented for the determination of the antihistaminic acrivastine (ACR) in capsules and urine. The first method utilizes the reaction of 2-nitrophenylhydrazine hydrochloride in presence of dicyclohexylcarbodiimide and pyridine. The violet colour of the resulting acid hydrazide is measured at 550 nm. The second method is based on alkaline oxidation of the drug with potassium permanganate and subsequent measurement of the formed manganate ion at 608 nm. The third method uses derivative spectrophotometry for the determination of ACR. The last method is extended to the in vitro determination of the drug in urine. All methods gave a relative standard deviation of less than 2%.     

A simple and rapid spectrophotometric method for determination of thiophanate-methyl in commercial formulations and its residues in foodstuffs

A new, simple, rapid, and sensitive spectrophotometric method for the determination of thiophanate-methyl, based on its reaction with cobalt(II) in the presence of triethylamine, has been developed. The yellowish green color that develops instantaneously on mixing the fungicide with the reagents in dimethylformamide is stable for at least 2 h and has maximum absorbance at 360 nm. The method has been successfully applied to the determination of thiophanate-methyl in its commercial formulations and residues on grains and apples. A photometric titration procedure for formulation analysis of the fungicide has also been developed.     

Measurement of the FMOC loading of protected amine-functionalised polymer beads

This paper presents an HPLC based procedure that has been developed for the determination of the 9-fluorenylmethoxycarbonyl (FMOC) content of protected amine-functionalised polymer beads. FMOC reagents are frequently employed both in the protection of amines and in their determination. The procedure utilises the stoichiometric base cleavage of dibenzofulvene from the protected amine using 1,8-diazabicyclo undec-7-ene. This stearically hindered base prevents the adduct formation that occurs with alternative base systems and measurement performance is enhanced by the incorporation of anthracene into the system as a non-reactive internal standard. HPLC separation of the reaction products permits the measurement of FMOC in the presence of additional chromophores that might otherwise impede direct measurement by UV-vis spectrophotometry. The procedure has been evaluated for the measurement of the FMOC content of protected amine-modified polymer beads employed in combinatorial solid phase synthesis.     

Spectrophotometric flow injection determination of formetanate and m-aminophenol in water after reaction with p-aminophenol

An automated procedure has been developed for the determination of formetanate and its metabolite m-aminophenol (MAP) in water samples. MAP can be selectively determined in the presence of formetanate by direct on-line reaction with p-aminophenol and spectrophotometric measurement of the absorbance at 576 nm in the presence of KIO(4), as oxidizing agent. The method has a limit of detection of 5 x 10(-7)M, it provides a recovery percentage from 95 to 104% and permits one to carry out 120 measurements/hr. The spectrophotometric determination of formetanate must be carried out after a previous hydrolysis to MAP. To determine formetanate in the presence of MAP, two steps are necessary. Firstly, the MAP content is selectively determined as has been mentioned above. After that, the sample is treated with 0.05M NaOH at 90' degrees C, to hydrolyze the formetanate to MAP, and then the sum of both is determined spectrophotometrically. The difference between the results obtained in each step gives the formetanate concentration. The developed procedure for the determination of formetanate provides a sensitivity of 1070 absorbance units mol(-1) l and a limit of detection of 1.9 x 10(-7)M, which corresponds to 50 mug/l of formetanate hydrochloride. The method has been applied to the analysis of natural water samples fortified with formetanate and MAP, and formetanate has also been quantitatively recovered in irrigation waters at a concentration level of 1.9 x 10(-6)M which corresponds to 500 mug/l. On the other hand, working in the stopped-flow mode, for a reaction time of 100 sec, the sensitivity of the formetanate determination can be increased to 4642 absorbance units mol(-1) l but the limit of detection remains of the order of 44 mug/l.     

Fluorescence Reaction of 5- (p-Methoxyphenylazo)-8-(p-tolylsulfonamido)quinoline with Cobalt(II) and Its Analytical Application

Abstract

5-(p-Methoxyphenylazo)-8-(p-tolylsulfonamido) quinoline(MTAQ) has been synthesized. The product was checked by IR, theroograviae-try, NMR and elemental analysis. A highly sensitive spectrofluorim-etric method has been developed for the determination of cobalt(II) based on the formation of a complex with MTAQ in slightly basic medium aqueous solution and In the presence of nonionic surfactant, tween-80. The complex shows two excitation maxima at 304 nm and 338 nm, its emission maximum is centred at 402 nm. The fluorescence intensity is proportional to cobalt(II) concentration in the range of 0-85 ppb. The method has good selectivity and has been applied to the direct fluorimetric determination of trace cobalt(II) in pig's liver, Dianchi shrimp and celery.     

Simultaneous (or sequential) determination of the total polyphenol index (or I280) and density in wines by flow injection

Flow injection methods for the determination of the total polyphenol index, the 'index 280' (I280) and dissolved solids in wines are proposed. The determination of the total polyphenol index is based on the Folin-Ciocalteu reaction in a basic medium and subsequent spectrophotometric detection at 750 nm. The direct measurement at 280 nm of the wine allows the determination of I280 with a simple manifold. The dissolved solids determination is based on the displacement of a light beam when the refractive index of the medium changes. This phenomenon, followed by a change in the absorbance in a photometric detector, usually takes place when an injected sample reaches the flow cell, and it is magnified on passage of the light beam in the radial direction instead of the more common axial direction. The use of a capillary (4 cm x 1.1 mm id) as the flow cell allows monitoring of the injected plug. A simple manifold coupled with a diode array spectrophotometer allows the determination of these parameters with a frequency of at least 90 h-1. Depending of the method adopted for the determination of polyphenols, Folin-Ciocalteu or I280, either a manifold different from that used for determining dissolved solids or the same, respectively, is required. The methods have been successfully applied to different wines and were substantiated well with official methods.     

Selective and stability-indicating methods for the simultaneous determination of mexiletine hydrochloride and/or its related substance: 2,6-dimethylphenol

Four simple, rapid, sensitive, and selective analytical procedures were developed for determination of mexiletine hydrochloride (MX) and/or its related substance: 2,6-dimethylphenol (DMP). The latter is a synthetic impurity for which a maximum pharmacopeial limit is defined. The first method depends on derivative-ratio spectrophotometry, for which the first-derivative signals of the ratio spectra at 259 nm (Deltalambda = 3 nm) are selected for the determination of MX. The second method is based on the spectrofluorometric measurement of MX in alkaline solution in the presence of 15 mM sodium dodecyl sulfate micellar medium at 292 nm (lambdaEx 260 nm). The third method is based on liquid chromatographic (LC) separation of MX and DMP on an RP-C8 column with a mobile phase consisting of 50 mM Na2HPO4-acetonitrile (60 + 40, adjusted to pH 2.4), and quantification of the analytes is achieved with UV detection at 212 nm based on peak area. The fourth method uses the coupling reaction of DMP with 2,6-dibromo-quinone-4-chlorimide (DBQC) in borate buffer to form an intensely colored product that was spectrophotometrically measured using first-derivative amplitudes at 670 nm (Deltalambda = 6 nm) for the determination of DMP. Different variables affecting each method were carefully investigated and optimized. The reliability and analytical performance of the proposed methods, including linearity, range, precision, accuracy, and detection and quantitation limits, were statistically validated. The first 3 methods were successfully applied for the stability-indicating determination of MX in laboratory-prepared mixtures with DMP, as well as for the determination of MX in capsules. Also, the LC and the DBQC spectrophotometric methods permitted the selective determination of DMP in the presence of a large excess of the parent drug at or near the pharmacopeial limit (0.1-1%).     

A Simple Spectrophotometric Method for the Determination of Adrenaline by Reaction with Copper(II)-Neocuproine

Abstract

A new facile and sensitive spectrophotometric procedure for the quantitative determination of adrenaline has been established. The method is based principally on the interaction of the compound with Cu(II)-neocuproine and subsequent measurement of the cuprous neocuproine chelate produced in the reaction at 458 nm. Optimization of the reaction conditions was conducted. Beer's law was obeyed in the concentration range 0.4-2.4 ppm of adrenaline. The method finally developed has been successfully applied for the assay of the drug in some of its pharmaceutical formulations.     

Spectrophotometric determination of some dibenzazepines with picryl chloride

A simple and sensitive spectrophotometric method has been developed for the determination of some dibenzazepines, based on reaction with picryl chloride in chloroform medium and measurement at 395 nm. Beer's law is obeyed in concentration ranges 0.1-1.0 microg/ml for imipramine hydrochloride, trimipramine maleate and opipramol dihydrochloride, 0.16-1.6 microg/ml for desipramine hydrochloride and 0.4-2.4 microg/ml for clomipramine hydrochloride. The method was applied successfully to the determination of dibenzazepines in tablets and the results were comparable to those obtained by official procedures.     

Kinetic determination of zineb in agricultural samples by continuous addition of reagent

The technique of automatic continuous addition of reagent has been applied for the determination of zineb in pesticides. The method is based on photometric monitoring of the fast complexation reaction between zinc(II) and Zincon. The special feature of the technique is the direct kinetic measurement, which provides a highly selective determination of zineb at mug/ml levels. The sampling rate of 140 samples/hr makes the method very useful in routine analysis for this pesticide in vine and olive leaves.     

Evaluation of a fluorometric-enzymatic method based on 3alpha-hydroxysteroid dehydrogenase for the mycotoxin zearalenone determination in corn

A new method for the fluorometric determination of zearalenone (ZEN) based on its reaction with βNADH in the presence of the enzyme 3α-hydroxysteroid dehydrogenase (3α-HSD) is described. The procedure is based on the change in fluorescence intensity that takes place during the enzymatic reaction (excitation at 340 nm and emission at 454 nm). The optimum reaction conditions and the analytical characteristics were studied; linear response range (1-10 mg l⁻¹) and reproducibility (8 mg l⁻¹, 2.7%, n=7). Moreover, a mathematical model explaining the analytical signal is proposed. The method has been applied to zearalenone determination in a spiked corn sample.     

Determination of neodymium by ion-exchanger absorptiometry with the f-f electron transition band

Summary Ion-exchanger absorptiometry, based on the direct measurement of light absorption by neodymium in the cation-exchange phase, has been developed for metal determination. In the presence of ethylenediaminetetraacetic acid (EDTA) about 99% of the neodymium in a 200-ml sample solution (pH 2.2 to 2.5) was concentrated in 0.50 g Muromac 50W-X12 cation exchanger within 15 min. EDTA does not interfere with the sorption of neodymium ions on the resin but suppresses spectrophotometric interference by ferric ions and ion-exchange saturation by ferric and thorium cations. The resin-phase attenuations at 740.5 nm and of the resin background at 620 nm were used for measurements with a 5-mm cell. Neodymium in the range 0.1 – 10 mg could be simply and rapidly determined without interference from other rare earths and the proposed method was used to analyse the rare-earth minerals and alloys.

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Bestimmung von Neodym durch Ionenaustauscherharz-Absorptiometrie mit Hilfe der f-f-Elektronenübergangsbande

     

Application of second derivative spectrophotometry for the determination of uranium in yellow cake

A derivative spectrophotometric method has been developed for the determination of uranium at mg level in presence of iron in 1M HNO₃ medium. Its application was extended to the determination of uranium is magnesium diuranate (Yellow Cake), an input material to the Uranium Conversion Plant. The second derivative absorbance at 408.2 nm was used for its quantification since at this wavelength the absorbance due to iron is negligibly small and that due to uranium is significant. The uranium content was found to be directly porportional to the amplitude at 408.2 nm. It was demonstrated that the impurities present in yellow cake do not interfere. The method is simple, fast, needs no prior separation and enables direct measurement of yellow cake samples which is an important requirement from the point of view of nuclear materials accounting.     

Extraction with long-chain amines-IV Separation and colorimetric determination of gold

A highly selective method, almost free from interferences, for extraction of gold(III) from sulphuric acid into a chloroform solution of trioctylamine (TOA) is described. The yellow extract is then measured at 325-330 nm. Gold can be determined in the presence of platinum. The method has been applied to the determination of gold in waste dumps. A more sensitive method is based on reaction of the gold with diphenylcarbazide after the separation of the gold from the TOA-chloroform extract. The violet colour is stable and is measured at 560 nm.     

Rapid Spectrophotometric Determination Of Osmium With Cyclohezane 1,3-Dione Bisthiosemicarbazone Monohydrochloride: Simultaneous Determination of Osmium and Platinum

Abstract

A simple, sensitive and rapid spectrophotometric method has been developed for the determination of osmium using cyclohexane 1,3-dione bisthiosemicarbazone mono-hydrochloride (1,3-CHDT.HCl). The method is based on the instantaneous colour reaction between 1,3-CHDT. HCl and osmium(VIII) in sodium acetate—acetic acid buffer medium (pH range 3–6). The osmium complex shows maximum absorbance at 375 nm and considerable absorbance at 510 nm. Although the complex formed between platinum(IV) and reagent (1,3-CHDT.HCl) shows maximum absorbance at 375 nm, it does not show any absorbance at 510 nm. Simultaneous determination of osmium and platinum is carried out when present alone and in presence of other foreign (associated) ions. Some physico-chemical and analytical characteristics of osmium and platinum complex are described. Interference of various foreign ions have studied and osmium is estimated selectively in the presence of constituents of platinum ores.