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 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.     

Alternating current polarographic determination of microgram amounts of iodide ion by means of the catalytic oxidation of 1-amino-2-naphthol-4-sulfonic acid

The catalytic oxidation of 1-amino-2-naphthol-4-sulfonic, acid proceeds quickly with microgram amounts of iodide in the presence of sodium chlorate at pH between 1.3 and 2.0. The oxidation product shows a sensitive tensammetric wave at potentials of about +0.03 V vs. SCE (pH 1.75), so that the catalytic reaction was applied for the determination of microgram amounts of iodide ion. The most suitable conditions of the pH range, the concentration of ANS and sodium chlorate, reaction temperature and standing are 1.3–2.0, 3 × 10^?4M, 0.05 M, 50° C and 1 h respectively. Using the recommended procedure, iodide ion can be determined precisely in the concentration range 0.4–6.5 ng ml^?1 with a relative error of about 3%. Interference of foreign species and the application to the determination of total iodine in river and sea water are described.     

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 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.     

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.     

Titrimetric determination of microgram amounts of manganese after amplification

Manganese (5-100mug) is oxidized to permanganate by periodate in 3 or 6% nitric acid. After masking of the excess ofperiodate with molybdate the permanganate and iodate formed are titrated iodimetrically.     

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.     

The determination of microgram amounts of beryllium using acetyl acetone

This paper describes the development of a method for the determination of μg quantities of beryllium using acetyl acetone. This reagent is first used to isolate the beryllium, after interfering elements have been complexed with ethylene diamine tetra-acetic acid. The beryllium is then determined absorptiometrically as the acetyl acetone complex using radiation of wavelength 2950 A. The method will detect 0.25 μg of beryllium with certainty and determine larger amounts with a precision of about ± 5 per cent.     

Catalytic determination of trace amounts of vanadium

Summary Some new oxidation reactions of arylamines catalysed by traces of vanadium have been found. It is shown that phenolic compounds have a favourable effect on these processes. Investigations were carried out on the oxidation ofp-phenetidine citrate by potassium chlorate in the presence of vanadium as catalyst and of phenol as activator. A colorimetric method for the determination of 0.1–8g of vanadium, based on this process, is reported.

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Zusammenfassung Einige neue, durch Vanadiumspuren katalysierte Oxydationsreaktionen von Arylaminen wurden gefunden. Phenolische Verbindungen haben auf diese Reaktionen erheblichen Einfluß. Die Oxydation vonp-Phenetidincitrat durch Kaliumchlorat bei Gegenwart von Vanadium als Katalysator und Phenol als Aktivator wurde untersucht. Eine kolorimetrische Methode zur Bestimmung von 0,1 bis 8g. Vanadium wurde auf dieser Grundlage ausgearbeitet.

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Résumé On a trouvé quelques nouvelles réactions d'oxydation des arylamines catalysées par des traces de vanadium. On montre que les composés phénoliques ont un effet favorable sur ces processus. On a effectué des recherches sur l'oxydation du citrate dep-phénétidine par le chlorate de potassium en présence de vanadium comme catalyseur et de phénol comme activateur. On présente une méthode colorimétrique pour le dosage de 0,1 á 8g de vanadium, fondée sur_ce procédé.

     

Kinetic-spectrophotometric determination of trace amounts of vanadium

A simple and sensitive kinetic-spectrophotometric method is described for the determination of vanadium and the possible mechanism of catalytic reaction is proposed. The method is based on the vanadium(V)-catalyzed oxidation of 1,8-diaminonaphthalene (DNA) by potassium bromate (Tiron as activator) at pH 3.8 and 40 degrees C. The reaction was monitored spectrophotometrically by measuring the increase in absorbance of oxidation products at 505 nm after a fixed time (6 min). The proposed method allowed the determination of vanadium in the range 0.025-15 ng ml(-1) with good precision and accuracy and the detection limit was down to 0.01 ng ml(-1). The method was found to be relatively selective and was applied successfully to the determination of vanadium in food and hair samples without previous separations. Recovery experiments have also been performed; excellent results were obtained.     

Spectrophotometric determination of microgram amounts of penicillins by solvent extraction with azure b

Penicillins are determined by means of ion-pair formation with azure B and extraction into chloroform: the absorbance of the extract is stable for several days. The apparent molar absorptivities for sodium penicillin G and potassium penicillin V at 634 nm are 3.91 × 10³ and 1.25 × 10⁴ l mol^-1 cm^-1, respectively. Calibration graphs are linear over the range 60–950 μg of sodium penicillin G and 40–600 μg of potassium penicillin V in 10 ml. The method is successfully applied to pharmaceutical preparations.     

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%).     

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.     

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.

     

The determination of microgram amounts of orthophosphate using ion-selective electrodes

Summary The potentiometric titration ofg amounts of orthophosphate with lead perchlorate using a lead ISE, and with silver nitrate using a silver sulfide ISE, was investigated. With 0.001N lead perchlorate the practical limit of the determination is approximately 10g (0.3mol) of phosphorus. Microgram amounts of phosphate require the application of a small polarizing current to the lead ISE to enhance the potential breaks near the endpoint.Previously reported titrimetric methods for orthophosphate with silver nitrate were reinvestigated using a silver sulfide ISE. The borate-buffered system proved superior to the sodium acetate-methanol system when a partially non-aqueous medium of 60–70% methanol was used. With the borate-buffered system, 0.005N silver nitrate can be used, while it cannot be used in the sodium acetate-methanol system. Also, considerably larger amounts of sulfate and fluoride can be tolerated in the borate-buffered system. The sequential determination of halides and phosphate is feasible in this system.

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Zusammenfassung Die potentiometrische Titration von Mikrogrammengen Orthophosphat mit Bleiperchlorat und einer bleispezifischen Elektrode bzw. mit Silbernitrat und einer silberspezifischen Elektrode wurde untersucht. Mit 0,001-n Bleiperchlorat liegt die praktische Grenze der Bestimmbarkeit bei etwa 10g (0,3Mol) Phosphor. Bei Mikrogrammengen Phosphat muß man an die bleispezifische Elektrode einen schwachen Polarisationsstrom anlegen, um den Potential-Knick nahe dem Endpunkt zu verstärken.Früher veröffentlichte Titrationsmethoden für Orthophosphat mit Hilfe von Silbernitrat wurden neuerlich mit einer Silbersulfidelektrode bearbeitet. Ein Boratpuffersystem erwies sich der Pufferung mit Natriumacetat-Methanol überlegen, wenn in 60–70%igem Methanol gearbeitet wird. In boratgepufferter Lösung kann man mit 0,005-n Silbernitrat titrieren im Gegensatz zu acetat-methanolischer Lösung. Auch können wesentlich größere Mengen Sulfat und Fluorid im boratgepufferten System toleriert werden. Halogenide und Phosphat können in diesem Milieu nacheinander bestimmt werden.

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This work was performed under the auspices of the U. S. Atomic Energy Commission.     

Spectrophotometric determination of microgram amounts of vitamin B1 with chloranil

Vitamin B₁ (20–200 μg) is determined spectrophotometrically using chloranil as π-acceptor at pH 9. The method is relatively rapid (10 min standing time), simple (the reaction occurs at room temperature), precise (RSD = 1.7%), and relatively accurate (error ⩽ ±3.0%).     

Iodometric determination of milligram and microgram amounts of levocetirizine in pharmaceuticals

Four simple, selective and sensitive methods are described for the determination of levocetirizine dihydrochloride (LCT) in bulk drug and in tablets. The methods exploit the well-known analytical reaction between iodide and iodate in the presence of acid solution. Iodide present is oxidized by iodate in an amount equivalent to the HCl present in LCT to iodine and the liberated iodine is determined by four different procedures which inturn quantify LCT at varying detection range and sensitiveness. Two direct titrimetric procedures involve titration of iodine by thiosulphate either towards starch end point (method A) or potentiometrically (method B). Both the methods have a reaction stiochiometry of 1: 1 (LCT: liberated iodine) and have quantification ranges of 2–20 mg LCT for method A and method B. The liberated iodine is also measured spectrophotometrically at 350 nm (method C) or the iodine-starch complex measured at 570 nm (method D). In both the methods, the absorbance is found to be linearly dependent on the concentration of iodine which in turn is related to LCT concentration. The calibration curves are linear over 5–40 and 1.25–12.5 mg mL^?1 LCT for method C and method D, respectively. The calculated molar absorptivity and Sandel sensitivity values are 1.0 × 10⁴ L mol^?1 cm^?1 and 0.0435 mg cm^?2, respectively for method C, and their respective values for method D are 2.9 × 10⁴ L mol^?1 cm^?1 and 0.0156 mg cm^?2. The intra-day and inter-day accuracy and precision studies were carried according to the ICH guidelines. The method was successfully applied to the analysis of two brands of tablets LCT. The accuracy was also checked by placebo blank and synthetic mixture analyses besides recovery study via standard addition procedure.     

The determination of microgram and sub-microgram amounts of boron : Absorptiometric determination using curcumin

Three methods are described for the absorptiometric determination of boron present in alkaline residues in a platinum dish. These are based on the reaction of boric acid and a curcumin reagent to form the red compounds rubrocurcumin and rosocyanin The first method is suitable for quantities of the element between about 2 and 15 μg, the second is best used when between 0.5 and 4 μg are present and the third when the highest sensitivity is required, 0.01–0.2μg. The last method does not involve the use of an oxalic acid promotor and is thought to give the maximum sensitivity possible for any absorptiometric technique. The three procedures were developed and have been used over the last decade for the analysis of atomic energy materials and have received very thorough testing under routine conditions.