Complexometric determination of aluminium, zirconium, and hafnium

Summary Methods for the complexometric titration of aluminium, zirconium and hafnium are described using pyrocatechol violet as indicator. The EDTA titration of zirconium and hafnium is performed in acid medium and that of aluminium in a solution buffered with acetate.

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Zusammenfassung Methoden zur komplexometrischen Titration von Aluminium, Zirkonium und Hafnium unter Verwendung von Brenzcatechinviolett als Indicator werden beschrieben. Die ÄDTA-Titration von Zirkonium und Hafnium erfolgt in relativ stark saurer Lösung, während die des Aluminiums in acetatgepufferter Lösung ausgeführt wird.

     

Simultaneous determination of arsenic,phosphorus, and silicon

Summary A simple, rapid, accurate and reliable method for the simultaneous determination of arsenic, phosphorus and silicon in the presence of each other is reported. The method involves the selective solvent extraction of phosphomolybdic acid by isobutyl acetate, the differential formation of phospho and arsenomolybdic acid when perchloric acid is added before the addition of ammonium molybdate, and the selective destruction of phospho and arsenomolybdic acid complexes in the presence of silicomolybdic acid. Silicon, phosphorus and arsenic were determined as their heteropoly blues.

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Zusammenfassung Eine einfache, rasche und verläßliche Methode zur gleichzeitigen Bestimmung von Arsen, Phosphor und Silicium nebeneinander wurde beschrieben. Phosphormolybdänsäure wird selektiv mit Isobutylacetat extrahiert. Setzt man vor der Zugabe von Ammoniummolybdat Perchlorsäure zu, so erfolgt die Bildung von Phospho- bzw. Arsenomolybdänsäure in differenter Weise. Diese beiden Säuren sind in Gegenwart von Silicomolybdänsäure selektiv zerstörbar. Silicium, Phosphor und Arsen werden auf der Grundlage der blauen Farbreaktion ihrer Heteropolysäure bestimmt.

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Résumé On communique une méthode simple, rapide, précise et sûre pour le dosage simultané de l'arsenic, du phosphore et du silicium en présence les uns des autres. La méthode met en jeu l'extraction par solvant sélectif de l'acide phosphomolybdique par l'acétate d'isobutyle, la formation différentielle de l'acide phospho et arsénomolybdique quand l'addition de l'acide perchlorique précède celle du molybdate d'ammonium, et la destruction sélective des complexes acides phospho et arsénomolybdiques en présence d'acide silicomolybdique. On a dosé le silicium, le phosphore et l'arsenic sous forme d'hétéropolycomplexes bleus.

     

Submilligram determination of carbon,hydrogen, and nitrogen

Summary The procedure described byFrazer ^4,6 for the simultaneous determination of carbon, hydrogen, and nitrogen has been scaled down to the submilligram level with no serious loss of accuracy. Approximately six complete determinations can be made in an eight-hour day. Whereas the accuracy depends to a large extent upon the analyst's technique, the method presented is comparatively straightforward. Analysts with no previous microanalytical training have been able to obtain results equivalent to the accuracy shown in Table I after two weeks of experience with the procedure.

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Zusammenfassung Die Methode vonFrazer ^4,6 für die gleichzeitige manometrische Bestimmung von Kohlenstoff, Wasserstoff und Stickstoff wurde ohne merkliche Einbuße an Genauigkeit in den Submilligramm-Maßstab übertragen. Ungefähr sechs vollständige Bestimmungen können innerhalb 8 Stunden ausgeführt werden. Obschon die erzielbare Genauigkeit stark von der Erfahrung des Analytikers abhängt, ist das Verfahren verhältnismäßig einfach. Analytiker ohne mikrochemische Erfahrung konnten nach zweiwöchentlicher Einübung Resultate erhalten, deren Genauigkeit denen der Tabelle 1 entspricht.

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Résumé Le procédé décrit parFrazer ^4,6 pour le dosage simultané du carbone, de l'hydrogène et de l'azote a été appliqué jusqu'à l'échelle du submilligramme sans perte sérieuse de précision. On peut effectuer approximativement six déterminations complètes en une journée de travail de huit heures. Comme la précision dépend dans une large mesure de la technique de l'analyste, la méthode présentée est relativement simple.Des analystes sans entraînement préalable en microchimie ont été capables d'obtenir des résultats avec la précision montrée sur le Tableau I, après deux semaines d'essai sur ce procédé.

     

Simultaneous determination of carbon,hydrogen, and nitrogen

Summary It was shown that carbon, hydrogen, and nitrogen can be determined simultaneously by the pyrolytic decomposition of the organic substance in a stream of oxygen in an empty combustion tube. Carbon and hydrogen are determined in the usual way, and nitrogen is determined from the sum of the amounts present as nitrogen oxides and as elementary nitrogen.     

Methods of extraction,preconcentration, and determination of quercetin

State-of-the-art methods of the extraction, preconcentration, and determination of quercetin and other flavonoids are described. Different methods of sample preparation of real samples are compared, including solvent extraction from solid matrices and liquid-liquid, supercritical fluid, and solid-phase extraction. The following main determination methods are discussed: HPLC, thin-layer chromatography, capillary electrophoresis, spectrophotometry, luminescence, and electrochemical methods. Some examples of quercetin determination in biological fluids, food products, biologically active food supplements, pharmaceutical preparations, and plant samples are given.     

微量铝的析相分离富集与测定方法

研究了铝 (Ⅲ )与 8 羟基喹啉 (HOx)反应生成疏水性络合物且被乳化剂(OP)增溶并析相富集于该表面活性剂中 ,加入水杨基荧光酮 (SAF)使其转变成了增敏多元有色配合物。考察了该体系的分析化学特性 ,探讨了析相、分离富集与显色反应的条件 ,共存离子的影响及其干扰离子的消除方法。并运用该体系对某铀矿区水样中的铝进行了测定     

Spectrophotometric determination of amikacin,kanamycin, neomycin and tobramycin

A spectrophotometric method for determination of neomycin, kanamycin, tobramycin and amikacin is proposed, based on the Rimini test with disodium pentacyanonitrosylferrate(II) for primary and secondary aliphatic amines. The absorbance of the coloured addition product is measured. Beer's law is valid over a wide concentration range. The method is relatively fast and can be used in control of the manufacture of the antibiotics and their purity, instead of the much slower microbiological method. It is also applicable for determination of these antibiotics in formulations.     

Spectrophotometric determination of copper, nickel, cobalt, iron and manganese as their pyridine thiocyanates Simultaneous determination in mixtures

Spectrophotometric determinations of copper, nickel, cobalt, iron, and manganese, based on the chloroform extraction of the metal pyridine thiocyanates, have been investigated. Optimum conditions require the pH of the aqueous solution to be in the range about 5–8; tartaric acid is used to prevent precipitation of hydrous oxides. An excess of pyridine must be used because chloroform readily extracts pyridine from the aqueous solution. Results are improved by making the extraction from a solution of high ionic strength (2 or above), which is provided by magnesium nitrate. Perchlorate decreases the absorbance, but the effect is essentially constant over a perchlorate concentration range of 0.8 to 2M. Although the metal pyridine thiocyanates are extracted by benzene, substituted benzenes, and halogenated hydrocarbons, chloroform is superior to other solvents in extraction efficiency and in colour stability of the extracted species. An example is given of the simultaneous determination of copper, nickel, cobalt, and iron in the same solution. Anions that also form metal pyridine compounds must be absent.     

The rapid isolation and determination of iridium after simultaneous liquid-liquid extraction and determination of platinum,palladium, rhodium and gold

The proposed method provides a rapid isolation of iridium form the other noble metals, as well as from Ni, Cu, Fe, Cr, Co and Na. The scheme comprises an initial removal of ruthenium and osmium by volatilization of their tetroxides followed by the simultaneous extraction of platinum, palladium, rhodium and gold as their 2-mercaptobenzothiazole—tin(II) chloride complexes into chloroform. Iridium in the raffinate is complexed by the same reagent system, after boiling, and extracted into chloroform. The extracts after evaporation of the solvent are converted to hydrochloric acid solutions and the noble metals are determined by atomic absorption spectrometry. Satisfactory results are obtained for various noble metal solutions, and for a solid platiniferous sample.     

Titrimetric determination of glucose,galactose, and xylose with n-bromosuccinimide

Summary N-Bromosuccinimide has been employed as a reagent for the determination of glucose, galactose, and xylose. The reactions are carried out at room temperature for 15 minutes. The errors involved are legs than ± 6% at the mg level. The time required for a complete determination is 45 minutes and the only standard solution required is sodium thiosulfate.

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Zusammenfassung N-Bromsuccinimid wurde als Reagens für die Bestimmung von Glukose, Galaktose und Xylose verwendet. Die Umsetzungen wurden in 15 Minuten bei Zimmertemperatur durchgeführt. Der Fehler beträgt im Milligrammbereich weniger als ± 6%. Für eine vollständige Bestimmung benötigt man 45 Minuten. Die einzig erforderliche Standardlösung ist Natriumthiosulfat.

     

Ultramicrocoulometric determination of ammonia in serum, plasma, and blood

A method has been developed for the ultramicrodetermination of ammonia in as little as 0.01 ml of serum, plasma, or blood by coulometric titration with electrogenerated hypobromite using a sensitive amperometric endpoint. The only accurate volumetric measurement required is the pipetting of the sample. The sample is added to a 33-mm microdiffusion cell for 10 min to separate the ammonia; the ammonia is collected in 0.1 ml of 0.0025 M sulfuric acid in the center compartment. The separated ammonia is added to a coulometric generation cell where an excess amount of hypobromite has been generated. The decrease in amperometric current due to the utilization of the hypobromite by the ammonia is taken as a measure of the ammonia content; comparison is made with diffused standards. An optimum pH of 8.6 for the titration has been found to give reproducible results at all levels encountered. One-tenth-milliliter blood samples are routinely analyzed. When elevated ammonia levels are encountered, 0.01-ml samples can be used with accurate results. The time for the analysis is 10–15 min after initiating the diffusion.     

Selective spectrophotometric determination of trinitrotoluene, trinitrophenol, dinitrophenol and mononitrophenol

Contaminated land and groundwater remediation in military waste dumping sites often necessitates the use of simple, cost-effective and rapid tests for detecting trinitrotoluene (TNT) and trinitrophenol (picric acid; PA) residues in the field along with their dinitro-analogues. Using PA as the model compound, a simple and field-adaptable (on-site) colorimetric method was developed for quantifying PA in the presence of dinitrophenol (DNP) and mononitrophenol (NP). Most commercialized methods for TNT assay—with the exception of CRREL method—use proprietary chemicals, and the color stability and intensity are highly dependent on the composition of the organic solution comprised of acetone or methanol. The developed colorimetric method here is based on the extraction of the Meisenheimer anion formed from the reaction of PA and aqueous NaOH into isobutyl methyl ketone (IBMK) with a cationic surfactant such as cetylpyridinium bromide (CPB). The orange-red color that developed in the organic phase was persistent for at least 30 min. TNT formed a similar extractable red complex under these conditions. If present, 2,4-dinitrophenol (DNP) and 4-nitrophenol (NP) could be detected by the same method at 17- and 167-fold concentrations of the LOD of PA, i.e. 1.5 ppm. DNP alone could be quantified by another charge-transfer (CT) agent, imidazole, as a yellow product at 400 nm in 98% EtOH solution. Under the same conditions, the intramolecular CT-band due to PA was essentially not intensified upon addition of the imidazole ligand, enabling the estimation of the DNP concentration from absorbance difference of solutions with and without imidazole, due to the intermolecular CT absorption of the latter. NP alone could be detected with a diphenylamine solution in H₂SO₄ to produce a blue color.