p-nitroaniline as a colorimetric reagent for sulphur dioxide

The merits of the nitroanilines as an alternative to p-rosaniline and fuchsine in the colorimetric determination of sulphur dioxide and sulphites have been investigated. p-Nitroaniline was found to be a stable, well-defined reagent, with which sulphur dioxide can be determined to a high level of precision, the sensitivity being of the same order of magnitude as for p-rosaniline.     

Determination of certain phenothiazine drugs with diazotized p-nitroaniline

A colorimetric method for the determination of 7 phenothiazine drugs by interaction with diazotized p-nitroaniline has been developed. Neither the degradation products of the drugs nor the common excipients in pharmaceutical preparations interfere.     

Potassium thiocarbonate as a complexing and spray reagent in inorganic thin-layer chromatography

Summary Clean and rapid micro analytical separations of metal ions of qualitative analytical groups 1 to 4 including some platinum metals have been made on silica gel G support by TLC using potassium thiocarbonate (PTC) as a complexing and visualising reagent. A review of the chromatographic behaviour of metal ions using PTC as a complexing and spray reagent in TLC is included.     

Colorimetric determination of theophylline and aminophylline with diazotized p-nitroaniline

The reactions of theophylline and aminophylline with diazotized p-nitroaniline in alkaline medium have been studied and developed into a sensitive assay for both drugs. The yellow azo-dyes formed with theophylline and aminophylline show maximum absorption at 440 and 410 nm respectively. Beer's law is valid within the concentration range 2–16 μg/ml for theophylline and 1–8 μg/ml for aminophylline. All variables which affect the reactions were studied and optimized. The proposed method has been successfully applied to determination of the drugs in their commercially available dosage forms. Statistical analysis of the results revealed that the proposed method is as precise and accurate as the official USP procedure.     

Spectrofluorimetric determination of 5-hydroxyindoles with benzylamine or 3,4-dimethoxybenzylamine as a selective fluorogenic reagent.

A spectrofluorimetric method has been developed for the sensitive and selective determination of 5-hydroxyindoles; the method is based on the reaction of 5-hydroxyindoles in a weakly alkaline solution (pH 9.0) with aromatic methylamines in the presence of potassium hexacyanoferrate(III) and dimethyl sulphoxide; the compounds produced fluoresce intensely in an alkaline solution (pH 11-12). Of the eight aromatic methylamines tested, benzylamine and 3,4-dimethoxybenzylamine were found to be the most favourable fluorogenic reagents in terms of sensitivity and reactivity. The methods with benzylamine and 3,4-dimethoxybenzylamine permit the determination of 5-hydroxyindoles at concentrations as low as 22-72 pmol ml-1 and 1.0-2.4 nmol ml-1, respectively.     

Spectrophotometric determination of aniline in aqueous solution by azo-dye formation with diazotized p-nitroaniline

A simple, sensitive, and rapid Spectrophotometric method for the trace determination of aniline in aqueous solution is described. The method is based on coupling aniline with diazotizedp-nitroaniline in the presence of ethanol and sodium hydroxide to form an intense red water-soluble azo-dye which shows maximum absorption at 505 nm and greater stability and sensitivity in the presence of cetyltrimethylammonium bromide. Beer's law is obeyed over the aniline concentration range 0.2–2.4g/ml in the solution measured; the molar absorptivity is 3.46×10⁴l· mole^–1·cm^–1, and the relative standard deviation 1–2%, depending on the aniline concentration.     

Quercetin as a spray reagent in inorganic thin-layer chromatography and evaluation of the chromatographed species by ring colorimetry

Summary Clean and rapid micro analytical separations of various ions in their mixed solutions have been made by the ascending TLC using quercetin (3,5,7,3,4-pentahydroxyflavone) as a spray reagent. For their evaluation, the visualized spots are scooped out with the help of Mottier gadget and transferred to the paper set on the ring oven. Separate rings were obtained for individual metal ions and the computation of their amounts is made possible by ring colorimetry, using suitable chromogenic reagents.

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Zusammenfassung Die exakte und rasche mikroanalytische Trennung verschiedener Ionen in deren Lösungsgemischen wurde durch aufsteigende Dünnschichtchromatographie unter Verwendung von Quercetin als Sprühreagens durchgeführt. Zur Auswertung wurden die sichtbar gemachten Flecken mit einem MottierGerät auf Papier übertragen und auf dem Ringofen bearbeitet. Für jedes einzelne Metall wurden verschiedene Ringe erhalten, die mit einem geeigneten Farbreagens behandelt zur kolorimetrischen Bestimmung dienten.

     

5-Amino-4-sulfanylphthalhydrazide as a chemiluminescence derivatization reagent for aromatic aldehydes in liquid chromatography

5-Amino-4-sulfanylphthalhydrazide (ASPH) was synthesized as a chemiluminescence derivatization reagent for aromatic aldehydes in liquid chromatography (LC). Benzaldehyde, 4-tolualdehyde, 4-chlorobenzaldehyde, 4-formylbenzoic acid, 4-hydroxybenzaldehyde and vanillin were used as model compounds to optimize the derivatization conditions. This reagent, ASPH, reacts selectively with aromatic aldehydes in the presence of sodium sulfite and disodium hydrogenphoshite in acidic medium at 100 degrees C to give the corresponding highly chemiluminescent 2-arylbenzothiazole derivatives. The resulting derivatives generated intense chemiluminescence by reaction with hydrogen peroxide and potassium hexacyanoferrate(III) in alkaline solution. The ASPH derivatives of aromatic aldehydes were separated by reversed-phase liquid chromatography with isocratic elution, and detected chemiluminometrically after mixing with oxidizing agents. The detection limits (signal-to-noise ratio = 3) for aromatic aldehydes are in the range 0.2-4.0 fmol for a 20-microl injection volume. Currently, the method is not effective for aliphatic aldehydes because of interfering LC peaks.     

Detection of amitraz,a formamidine-based pesticide using chromogenic spray reagent by thin-layer chromatography

JPC – Journal of Planar Chromatography – Modern TLC - In the present study, we developed a simple, sensitive and selective thin-layer chromatographic method for the detection and...     

Glyoxal dithiosemicarbazone as a complexing and chromogenic spray reagent in inorganic TLC

Summary Systematic TLC separations, identification of cations and the determination of the limits of their identification on microcrystalline cellulose layers, incorporating glyoxal dithiosemicarbazone (H₂-GDTS) as a spray reagent have been worked out. Metal-GDTS complexes have also been separated on silica gel G support. Detection called for no spray reagent, owing to the intense and characteristic colours of the complexes.     

Redox reactions in a number of pyrrole-ring-substituted 5-hydroxyindoles

Some 3-substituted 5-hydroxyindoles are smoothly hydrogenated in acid media in the presence of a palladium catalyst to the corresponding indolines, which in turn are readily oxidized by air oxygen in aqueous solutions at pH 10 to the corresponding 5-hydroxyindoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1058–1061, August, 1971.     

A new spray reagent for selective detection of dichlorvos by thin-layer chromatography

The misuse of dichlorvos (DDVP), an organophosphorus insecticide, results in many instances of poisoning. This paper describes a new spray reagent for selective detection of dichlorvos in biological materials by thin-layer chromatography. Dichlorvos in presence of moisture breaks down to dichloroacetaldehyde which in turn reacts with phenylhydrazine hydrochloride to give a yellowish red colour. In acidic media the colour is intensified and consequently the sensitivity of detection increases. The reagent is selective for dichlorvos, other organophosphorus insecticides failed to give a coloured spot. Moreover organochlorine, carbamate and synthetic pyrethroid insecticides or even constituents of visceral extracts (amino acids, peptides, proteins etc.) do not interfere. The limit of detection is ca 10 mug.     

Phosgene as a derivatizing reagent prior to gas and liquid chromatography

The use of phosgene as a derivatizing agent for bifunctional compounds prior to gas and liquid chromatographic analysis is reviewed. Applications include gas chromatographic determinations of metoprolol and its metabolites in biological fluids, enantiomeric separations of beta-blocking drugs and sympathomimetic agents on a chiral stationary phase and liquid chromatographic enantiomer separations.     

2-Formyl-5-nitrothiophene as a reagent for phosphoranes

2-Formyl-5-nitrothiophene has high reactivity with respect to phosphoranes, with which it reacts quantitatively to give l-aryl-3-(5-nitro-2-thienyl)propenones. The reaction can be used for the qualitative detection of phosphoranes.     

5:6-Benzoquinaldinic acid as a colorimetric reagent

5:6-Benzoquinaldinic acid, like α-picolinic acid, has been utilised as a colorimetric reagent for iron (ous). Transmittancy measurements with the Lumetron 402 EF having a cell of capacity 16 ml and thickness 20 mm show that iron from 0.4 to 20 p.p.m. may be estimated, while that with Klett-Summerson photoelectric colorimeter, iron from 5 to 50 p.p.m. may be determined in a tube cell of capacity 15 ml and diam. 12 mm. The optimum range with the minimum error is from 2.4 to 14 p.p.m. The effect of diverse ions, reagent, reducing agent, cyanide and other physical conditions as temperature, time, etc. on the colour system has been investigated.     

3-Iodoacetylaminobenzanthrone as a fluorescent derivatizing reagent for thiols in high-performance liquid chromatography

A new thiol-reactive derivatizing reagent, 3-iodoacetylaminobenzanthrone (IAB) has been developed for thiol analysis in liquid chromatography. In aqueous methanol containing 15 mM pH 8.3 H₃BO₃-KCl-Na₂CO₃ buffer, IAB reacted with thiols at 35 °C for 15 min. The derivatives of IAB with glutathione (GSH), cysteine (Cys), homocysteine (Hcy) and N-acetylcysteine (Nac) were well separated on a C₁₈ column with the mobile phase of methanol-water (50:50, v/v) containing 15 mM pH 2.7 H₃cit-Na₂HPO₄ buffer. At λ_ex/λ_em=420/540 nm, the detection limits were 20, 20, 55 and 40 fmol (1, 1, 2.3 and 2 nM), respectively, with a signal-to-noise ratio of 3. Owing to the preferential selectivity of iodoacetamidyl moiety to SH group, amino acids, aliphatic amines, phenol and alcohols had no obvious interference with the determination. The proposed method has been applied to the determination of thiols in human blood with recoveries of 98.5-105.3%.