Polarographic determination of microgram amounts of thorium(IV)

Summary Among various salt solutions tested 0.01 N LiNO₃ proved to be most suitable as supporting electrolyte for the polarographic determination of microgram amounts of thorium. Well-developed, maxima-free and reproducible waves were obtained for a Th(IV) concentration range of 1.4–23 g/ml. The minimum detectable limit of the element was 0.8 g/ml. No relationship has been found between Th(IV) and H⁺-ion concentration.

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Polarographische Bestimmung von Mikrogramm-Mengen Thorium(IV)

Zusammenfassung Von verschiedenen untersuchten Salzlösungen hat sich als Grundelektrolyt 0,01 N LiNO₃-Lösung als am günstigsten erwiesen. Es wurden damit gut ausgebildete, maxima-freie und reproduzierbare Stufen für einen Konzentrationsbereich von 1,4–23 g Th(IV)/ml erhalten. Die Nachweisgrenze betrug 0,8 g Th(IV) in 1 ml Lösung. Es wurde kein Zusammenhang zwischen Thoriumkonzentration und H⁺-Ionenkonzentration nachgewiesen.

     

Filter-paper test for microgram detection of aliphatic amines

A new simple, sensitive and selective test for the detection of microgram amounts of aliphatic amines with diphenylcarbazide-soaked Whatman No. 1 filter paper as the detection medium is described. A feature of the study is the observation that the reaction does not take place in solution in the absence of the filter paper.     

Copper(II) acetates with aliphatic/heterocyclic amines

Summary Three copper acetate complex compounds, namely Cu(CH₃COO)₂(en)₂·2H₂O (I), Cu(CH₃COO)₂(tn)₂(II) and Cu₂(CH₃COO)₄(pyz) (III) (en=ethylenediamine, tn=1,3-diaminopropane, pyz=pyrazine), were prepared and characterized during heating in argon by thermogravimetry (TG), differential thermal analysis (DTA) and evolved gas analysis (EGA) using mass spectrometry (MS). The results of infrared spectroscopy (IR) were evaluated to be used as a spectroscopic criterion for the determination of the carboxylate binding mode in the compounds.     

Spectrophotometric determination of microgram amounts of chlorpromazine with chloranil

A simple spectrophotometric method for the determination of small amount of chlorpromazine has been developed. The reaction of chloranil as π-acceptor reagent with chlorpromazine was studied. The method is rapid, simple, and relatively sensitive and precise (RSD 1.8%). Beer's law was followed within the approximate concentration range of 50–900 μg in a final volume of 25 ml. Negative deviation was abserved beyond these limits. The general analytical and physical parameters were also established.     

Spectrofluorimetric determination of microgram amounts of lead

The violet fluorescence at 480 mmu of lead in concentrated hydrochloric acid-potassium chloride solution (excitation maximum 270 mmu) provides a method for the spectrofluorimetric determination of 10-60mug of lead. The optimum conditions for the determination have been established, and the effect of 31 foreign ions examined at the 50-fold molar excess level. The interference from iron(III) and vanadium(V) is eliminated by addition of tin(II) chloride, and that of chromium(VI) by treatment with sodium sulphite.     

Spectrophotometric determination of microgram amounts of ampicillin with chloranil

Ampicillin trihydrate (12.5–750 μg) is determined spectrophotometrically using chloranil as π-acceptor at pH 9. The method is relatively accurate (with a recovery of 100 ± 1.0%) and precise (RSD ⩽ 1.7%) and can be used successfully for capsules and ampoules.     

Spectrophotometric determination of microgram amounts of platinum

2-Ethyl-10-[3-(dimethylamino-2-methyl)propyl]phenothiazine hydrochloride (ethylisobutrazine hydrochloride) forms an orange-red complex with platinum(IV) at room temperature (26 ± 2 °C) in hydrochloric acid-sodium acetate buffer medium containing copper(II) ions. The complexation is complete within 10 min. The complex exhibits an absorption maximum at 529 nm with a molar absorptivity of 1.90 × 10⁴ liters mol^?1 cm^?1. Beer's law is obeyed over the concentration range 0.4–7.8 ppm of platinum. A 50-fold molar excess of the chromogenic reagent is necessary for the development of maximum color intensity. Job's method of continuous variation, the molar-ratio method, and the slope-ratio method indicate a 1:1 composition for the complex. The effects of pH, time, temperature, reagent concentration, order of addition of reagents, and interference of various ions are reported. The reagent has also been used successfully for the determination of platinum in minerals and alloys.     

Spectrophotometric determination of microgram amounts of amino acids with chloranil

Amino acids form molecular complexes with chloranil at pH 9.0 having apparent molar absorptivities at 350 nm ranging from 4,000 to 28,000. A spectrophotometric method for the determination of μg amounts of amino acids is described, based on such complex formation. There is no interference from urea and only a weak interference from ammonium ions.     

Spectrophotometric determination of microgram amounts of aromatic aldoximes with chloranil

Benzaldoxime and its p-hydroxy, methyl, chloro and nitro derivatives (50–500 μg) are determined by using chloranil as a π-acceptor at pH 9. The method is simple, precise (r.s.d. <3%) and accurate (±2%).     

Claisen rearrangement of aliphatic allyl vinyl ethers in the presence of copper(II) bisoxazoline

The Claisen rearrangement of 1-methyl-2-isopropyoxycarbonyl-6-propyl allyl vinyl ether catalyzed by copper(II) bisoxazoline (Cu-box) has been investigated using density functional theory. Both the phenyl- and tert-butyl-substituted Cu-box systems have been studied. Three different reaction media (vacuum, CH2Cl2, CH3CN) have been considered. In vacuum, the phenyl Cu-box catalyzed reaction yields a (1R,6R) configured major product with a low selectivity. The solvent induces a higher selectivity and a reversal of the absolute configuration (1S,6S). However, the tert-butyl Cu-box catalyzed reaction yields (1R,6R) as the major product both in the gas phase and in the solvent with a good selectivity. Although chair-like TSs are lower in energy than boat-like TSs, the energy difference is small. This is because in the presence of the catalyst the distance between the allyl and vinyl parts of the substrate is relatively large, and thus the steric repulsion between them is smaller than would normally be expected for boat-like structures. The enantioselectivity of tert-butyl Cu-box originates from the steric interactions between the substrate and the catalyst, which are less important for the phenyl Cu-box where the enantioselectivity is determined by the solvent effects.     

Improvements in the gas chromatographic determination of trace amounts of aliphatic amines in aqueous solution

The analysis of aliphatic amines at the parts per million level in aqueous solution has been improved with respect to a previously reported chromatographic method which made use of Carbopack B modified with 0.8% potassium hydroxide and 4% PEG 20M by altering these concentrations to 0.3% and 4.8%, respectively, by using a modified coating procedure. By this means, difficulties in duplicating from batch to batch the chromatographic characteristics of the column packing have been eliminated, and the instability of the retention times of amines on prolonged use of the column, the intolerance of the packing to injections of water and overlapping of tailed peaks for alcohols with the amine peaks no longer affect the trace determination of amines.     

Absorptiometric determination of microgram amounts of uranium with Rhodamine B

Uranium (VI) can be extracted as a complex with rhodamine B into a benzeneetherhexone solvent from a benzoate buffered solution. Optimum conditions for the colour development are defined, leading to a molar absorptivity of 102700 mmol^-1 cm² at 555 nm, the highest yet reported for a uranium complex. The determination of uranium in the range 0.02–3 μg/ml in nitrate samples is described. The relative standard deviation ranges from 20 to 0.6%. The interference of several ions is investigated.     

Selective titration of microgram amounts of copper with photometric end-point detection

The reaction of copper ions with pyridylazonaphthol is very suitable and sensitive for the photometric titration of copper. The titration is self-indicating, and at the 0.1-ppm level the standard deviation is 2.5%. The main interferences are caused by bismuth, iron, titanium and vanadium but can be overcome by suitable masking.     

The spectrophotometric determination of microgram amounts of cerium

A spectrophotometric procedure, which has a coefficient of variation of ca. 2%, is described for the determination of up to 80 μg of cerium. Ceric ion formed by oxidation with persulphate, in the presence of catalytic amounts of silver, is reduced to the cerous state by treatment with excess ferrous-phenanthroline reagent. The decrease in optical density of the ferrous-phenan-throline compared with the reagent blank is a measure of the amount of cerium present. The only common cations which cause serious interference are Mn⁺²and Cr⁺³.     

Spectrophotometric determination of cobalt(II) in the presence of large amounts of iron with salicylaldehyde thiosemicarbazone

Cobalt(II) reacts instantaneously with the reagent at pH 5.0. The yellow complex has a molar absorptivity of 1.1 × 10⁴ 1 mol^?1 cm^?1. The method is applied to the determination of cobalt in steels after removal of iron with phosphate.     

Spectrophotometric determination of iron(II) with 1,10-phenanthroline in the presence of large amounts of iron(III)

A study was made to establish proper conditions for the selective determination of Fe(II) by the 1,10-phenanthroline method in the presence of large amounts of Fe(III). It was shown that fe(III) is effectively masked by fluoride. The pH of the solution to be masked should be below 2.5 in order to prevent acceleration by the fluoride of aerial oxidation of Fe(II).     

Catalytic spectrophotometric determination of trace amounts of copper(II) with 3-hydroxy-2-naphthoic acid

A very sensitive catalytic spectrophotometric method for the determination of copper(II) concentrations as low as 0.06 ng/ml is described. This method is based on the oxidation of 3-hydroxy-2-naphthoic acid by hydrogen peroxide in ammoniacal medium, catalysed by copper(II). The results of an exhaustive study of interferences are given. The new method is applied to determination of copper in atmospheric aerosol samples. A qualitative study of the mechanism by means of electron paramagnetic resonance spectroscopy is also included.