Spectrofluorimetric determination of benzodiazepinooxazoles

Summary A study of fluorescence properties of Cloxazolam and Oxazolam has been carried out. pK_a-values were calculated and a spectrofluorimetric method was developed in acidic hydroalcoholic medium for the determination of the drugs. The fluorescence intensity was linear with the concentration up to at least 6.00×10^–6 mol/l for Cloxazolam and 5.17×10^–6 mol/l for Oxazolam. Detection limits obtained were 2.91×10^–8 mol/l and 4.56×10^–8 mol/l for Cloxazolam and Oxazolam, respectively. Spectrofluorimetric methods were applied to the determination of both drugs in pharmaceuticals and errors lower than 2.5% were obtained. Spectrophotometric determination methods were also developed.     

Continuous-flow chemiluminescence determination of isoniazid by oxidation with N-bromosuccinimide

A rapid and precise continuous-flow method is described for the determination of isoniazid (0.050-20.0 micrograms ml(-1)) based on the chemiluminescence produced during its reaction with N-bromosuccinimide in alkaline medium. The emission intensity is greatly enhanced by the presence of ammonia. The procedure is automated and samples can be analysed at a rate of 112 solutions per hour with a relative error of about 2%. When applied to tablets, the method is relatively free from interferences from common excipients and co-existing compounds. The results obtained for the assay of commercial preparations compared well with those obtained by an official chemical method and demonstrated good accuracy and precision.     

Milligram determination of aromatic amines and phenols with N-bromosuccinimide

A simple and rapid method has been developed for the determination of milligram amounts of aromatic amines and phenols. An aliquot containing 2-4 mg of sample is dissolved in a mixture of hydrochloric and acetic acids and allowed to react with N-bromo-succinimide, the excess of which is determined iodometrically after the reaction is over. The reaction time varies from 1-10 min and the absolute error generally is negative, ranging from -1 to -4%.     

Spectrofluorimetric determination of malic acid with β-naphthol

A detailed study of the spectrofluorimetric determination of malic acid by reaction with /gb-naphthol is reported. As little as 0.1 /smg of malic acid can be determined. The optimum concentration of sulfuric acid is 80% (v/v). The interferences of citric, succinic and tartaric acids are discussed.     

Spectrofluorimetric determination of 1,4-thienodiazepines

The fluorescence characteristics of four 1,4-thienodiazepines in aqueous and methanolic solutions and the effect of pH on fluorescence intensity are described. The pK_a values are calculated. Fluorimetric methods with limits of detection between 3 and 38 ng ml^?1 were developed, and applied for determinations of one drug in tablets, and the others in serum after extraction with a Sep-Pak C₁₈ cartridge.     

Spectrofluorimetric flow-injection determination of cyanide

The spectrofluorimetric determination of cyanide (0.1–20 μg ml^?1) with pyridoxal and pyridoxal-5-phosphate by a normal flow-injection method and a stopped-flow procedure is reported. The large number of interfering species in the normal method is significantly decreased by the use of the stopped-flow method. The relative standard deviation is <2%.     

Fluorometric determination of nitrite with acetaminophen

A simple, sensitive and selective fluorometric method for the determination of nitrite is described. The fluorometric determination is based on the reaction of acetaminophen with nitrite in an acidic medium followed by alkalinization of the reaction which yields a highly fluorescent product, exhibit (λ_ex/λ_em=325/430 nm). The optimum experimental conditions were studied. The fluorescene intensity is linear over a nitrite concentration of 0.08–1.3 μg/ml with a detection limit of 2.7 ng/ml (S/N=3). The effect of interferences from various metals/ions were studied. The proposed method is accurate, reproducible, shows satisfactory results and compares successfully with the reference method.     

Spectrofluorimetric determination of traces of bromide

A Spectrofluorimetric method for the determination of traces of bromide has been developed. The method is based on the bromination of fluorescein after bromide and hypochlorite form bromine, giving the less fluorescent eosin. The fluorescence decrease is used as the analytical signal. The calibration graph is linear over the range 10 to 80 g/1. The detection limit is 3 g/1 and the relative standard deviation 1.0%. The method has been satisfactorily applied to the determination of bromide in natural waters.     

Titrimetric determination of octacyanotungstate(IV) ions with N-bromosuccinimide

Summary N-Bromosuccinimide has been successfully applied in the determination of 1–50 mg of W(CN)₈ ^4–in approximately 6 M hydrochloric acid using Naphthol Blue Black indicator. The average error is ±0.42% and the average standard deviation is ±0.06 mg. The method is not applicable to the determination of Mo(CN) ₈ ^4– ions. Tetrakis-(N-hydro-2-carbocyclic acid-pyridinium)octacyanotungstate(IV) and -molybdate(IV) were used as primary standards for the preparation of standard Mo(IV) and W(IV) solutions. The composition of the latter compounds was verified by analysis and single crystal X-ray data were obtained.

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Titrimetrische Bestimmung von Octacyanowolframat(IV)-ionen mit N-Bromsuccinimid

Zusammenfassung N-Bromsuccinimid wurde mit Erfolg zur Bestimmung von 1–50 mg W(CN)₈ ^4–-Ionen in ungefähr 6 M Salzsäure mit Naphthol-Blau-Schwarz als Indicator verwendet. Der mittlere Fehler beträgt ±0,42 %, die mittlere Abweichung ±0,06 mg. Die Methode ist nicht brauchbar für die Bestimmung von Mo(CN)₈ ^4–-Ionen. Tetrakis(N-hydro-2-carbonylsäure-pyridinium) octacyanowolframat(IV) und -molybdat(IV) wurden als Primärstandards für die Herstellung von Standard-Mo(IV)- und -W(IV)-Lösungen benutzt. Die Zusammensetzung dieser Verbindungen wurde durch Analyse kontrolliert und die Einkristall-Röntgen-Daten wurden festgestellt.

     

Spectrofluorimetric determination of traces of indium with 5-chiorosalicylidene-o-aminophenol

A Spectrofluorimetric method for microdetermination of indium, based on the formation of a fluorescent 21 (ligand:metal) complex between In (III) and 5-chlorosalicylidene-o-aminophenol at an apparent pH of 4.70 in an aqueous-ethanol medium (50% v/v ethanol) is proposed. The calibration graph is linear over the range 10.0–80.0 g/l, the relative standard deviation 2.7% and the detection limit 1.5 g/l. The method has been applied to the determination of indium in synthetic samples and natural waters.     

Spectrofluorimetric determination of triethylenethiophosphoramide in blood

The method is based on a reaction of the ethyleneimine group with sodium sulfide, taurine and o-phthalaldehyde to give a fluorescent product. Triethylenethiophosphoramide (thioTEPA) can be determined in the range 9.4–945 ng in 100 μl of 1-propanol with a relative standard deviation of 2.3–4.7%. The method is applied to the determination of thioTEPA in rabbit blood plasma. The use of Extrelut 3 proved to be efficient for the clean-up of thioTEPA in plasma samples.     

Spectrofluorimetric determination of Er (III) with diantipyrylmethane

The optimum fluorescence conditions for erbium (III) are obtained by irradiating this lanthanide at 435 nm in 0.04 microg ml(-1) diantipyrylmethane solution at pH = 8 (lambdaem = 510 nm). The method proposed is satisfactory for the determination of erbium (III) in the range of 0.001 to 1 microg ml(-1). The relative standard deviation 0.02 microg ml(-1) Er (III) in 0.04 microg ml(-1) diantipyrylmethane solution is 1.1%. The effect of other rare earths upon the intensity of the fluorescence emitted by erbium (III) is discussed.     

Spectrofluorimetric determination of some water-soluble vitamins

Two simple and sensitive spectrofluorimetric methods were developed for determination of three water-soluble vitamins (B1, B2, and B6) in mixtures in the presence of cyanocobalamin. The first one was for thiamine determination, which depends on the oxidation of thiamine HCl to thiochrome by iodine in an alkaline medium. The method was applied accurately to determine thiamine in binary, ternary, and quaternary mixtures with pyridoxine HCl, riboflavin, and cyanocobalamin without interference. In the second method, riboflavin and pyridoxine HCl were determined fluorimetrically in acetate buffer, pH 6. The three water-soluble vitamins (B1, B2, and B6) were determined spectrofluorimetrically in binary, ternary, and quaternary mixtures in the presence of cyanocobalamin. All variables were studied in order to optimize the reaction conditions. Linear relationship was obeyed for all studied vitamins by the proposed methods at their corresponding lambda(exc) or lambda(em). The linear calibration curves were obtained from 10 to 500 ng/mL; the correlation ranged from 0.9991 to 0.9999. The suggested procedures were applied to the analysis of the investigated vitamins in their laboratory-prepared mixtures and pharmaceutical dosage forms from different manufacturers. The RSD range was 0.46-1.02%, which indicates good precision. No interference was observed from common pharmaceutical additives. Good recoveries (97.6 +/- 0.7-101.2 +/- 0.8%) were obtained. Statistical comparison of the results with reported methods shows excellent agreement and indicates no significant difference in accuracy and precision.