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.     

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%).     

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.     

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.     

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%).     

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 trace amounts of cadmium and lead with iodide and Rhodamine B

Summary Highly sensitive spectrophotometric methods have been developed for determination of cadmium and lead, based on the CdI₄ ^2– or PbI₄ ^–2 anionic complexes with Rhodamine B in the presence of polyvinyl alcohol to form ion-association complexes. The molar absorptivity is 4.2×10⁵l·mole^–1·cm^–1 at 600 nm for cadmium and 5.7×10⁵l·mole^–1·cm^–1 at 610 nm for lead. The complexes have the composition [CdI₄ ^2–]·[RhB⁺]₂ and [PbI₄ ^2–]·[RhB⁺]₂ as established by Job's method of continuous variations and the molarratio method. The colour reaction selectivity is fairly good and the method can be applied for direct spectrophotometric determination of cadmium or lead in some pure metals. A species [PbI₃ ^–]·[RhB⁺] can also be formed, and extracted into toluene or a toluene/diethyl ether mixture.

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Spektrophotometriscbe Bestimmung von Spuren Cadmium und Blei mit Jodid und Rhodamin B

Zusammenfassung Hochempfindliche spektrophotometrische Methoden für die Bestimmung von Cadmium und Blei wurden entwickelt; sie beruhen auf der Reaktion von CdJ₄ ^2– bzw. PbJ₄ ^2– mit Rhodamin B in Gegenwart von Polyvinylalkohol unter Bildung von Ionenassoziat-Komplexen. Die molare Absorptivität für Cadmium beträgt 4,2×10⁵l·mol^–1·cm^–1 bei 600 nm und für Blei 5,7×10⁵l·mol^–1·cm^–1 bei 610 nm. Wie nach der Methode der kontinuierlichen Variation nach Job bzw. mittels Molarverhältnis ermittelt wurde, lautet die Formel [CdJ₄] [RhB]₂ bzw. [PbJ₄] [RhB]₂. Die Selektivität der Farbreaktion ist gut. Das Verfahren kann zur direkten spektrophotometrischen Bestimmung von Cadmium bzw. Blei in verschiedenen reinen Metallen verwendet werden. Auch eine Verbindung [PbJ₃ ^–] [RhB⁺] kann hergestellt werden, die sich mit Toluol oder mit einem Gemisch aus Toluol und Diethylether extrahieren läßt.

     

Spectrophotometrie determination of microgram quantities of hexavalent uranium

Summary A method is presented for the spectrophotometric determination of microgram amounts of hexavalent uranium by means of the azodyes Monochrome Black Blue G und Diamond Black PBB respectively.These two azodyes react with uranyl ions in an acetate buffered hydrochloric acid-methanolic medium under formation of colored chelates. 10 or 20 g uranium(VI)/10 ml measuring solution can still be determined with relatively high accuracy.

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Zusammenfassung Es wird eine Methode zur spektrophotometrischen Bestimmung von Mikrogrammengen Uran(VI) mittels der Azofarbstoffe Monochromschwarzblau G bzw. Diamantschwarz PBB angegeben. Diese beiden Azofarbstoffe reagieren mit Uranylionen in acetatgepuffertem salzsauermethanolischem Medium unter Bildung gefärbter Chelate. 10 bzw. 20 gUran(VI)/10ml Meßlösungkönnennoch mitrelativ hoher Genauigkeit bestimmt werden.

     

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 and submicrogram amounts of silver with thio-Michlers ketone

Summary 4,4-bis-(dimethylamino-)thiobenzophenone (thio-Michler's ketone, TMK) has been found to be more sensitive than the commonly known silver reagents such as dithizone, diethylaminobenzylidenerhodanine, and pyrogallol red. Silver reacts with TMK at p_H 3.0 ± 0.2 forming a 1-to-1 red complex with two absorption maxima, 480 nm and 520 nm. The latter is recommended for the absorbance measurement. The silver-TMK complex can be extracted with isoamyl alcohol orn-hexanol or its color may be developed in a 60% ethanol or methanol solution. Procedures are described for determining silver in microgram and submicrogram amounts. The sensitivity and absorptivity of the silver TMK complex are found to be 0.001 and 93800, respectively. Like most silver compounds, the silver TMK complex must be protected from light. The use of amber glass separatory funnels is recommended. Silver may be determined with TMK in the presence of tartaric acid and EDTA. New color reactions of TMK with other elements in the presence of ascorbic acid are reported.

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Zusammenfassung 4,4-Bis(dimethylamino)-thiobenzophenone (Thio-Michlers Keton, TMK) ist als Reagens für Silber sensitiver als die üblichen Silberreagenzien wie Dithizon, Diäthylaminobenzylidenrhodanine oder Pyrogallolrot. Silber bildet mit TMK bei p_H 3,0±0,2 einen roten 11-Komplex mit zwei Absorptionsmaxima bei 480 und 520 nm. Letzteres wird für die Messung empfohlen. Der Silber-TMK-Komplex kann entweder mit Isoamylalkohol oder n-Hexanol extrahiert werden, oder man führt die Farbreaktion in 60%ig äthanolischer oder methanolischer Lösung aus. Arbeitsweisen zur Bestimmung von Mikrogramm- und Submikrogramm-Mengen Silber werden angegeben. Empfindlichkeit und Absorptionswert des Silber-TMK-Komplexes betragen 0,001 bzw. 93800. Wie die meisten Silberverbindungen muß auch dieser Komplex vor Licht geschützt werden, daher wird empfohlen, Scheidetrichter aus dunklem Glas zu verwenden. Die Silberbestimmung mit TMK kann auch in Gegenwart von Weinsäure oder ÄDTA durchgeführt werden. Über neue Farbreaktionen von TMK mit anderen Elementen in Gegenwart von Ascorbinsäure wird berichtet.

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Résumé On a observé que la bis-(diméthylamino)-4,4-thiobenzophénone (thiocétone de Michler, TCM) était plus sensible que les réactifs de l'argent habituels, comme la dithizone, la diéthylammobenzylidènerhodanine et le rouge de pyrogallol. L'argent réagit avec la TCM à p_H 3,0±0,2 en formant un complexe rouge avec deux maximums d'absorption à 480 et 520 nm. Le dernier est recommandé pour la mesure de la densité optique. On peut extraire le complexe de la TCM avec l'argent par l'alcool isoamylique ou l'hexanol N; on peut aussi développer la coloration dans une solution d'éthanol ou de méthanol à 60%. Les modes opératoires sont décrits pour le dosage de l'argent en quantités de l'ordre du microgramme ou du submicrogramme. On a trouvé que la sensibilité et la capacité d'absorption du complexe de la TCM avec l'argent étaient respectivement de 0,001 et de 93800. Comme pour la plupart des composés de l'argent, on doit protéger le complexe Ag-TCM de la lumière. On recommande l'emploi d'entonnoirs à décantation en verre ambré. On peut doser l'argent avec la TCM en présence d'acide tartrique et d'EDTA. On décrit de nouvelles réactions colorées de la TCM avec d'autres éléments en présence d'acide ascorbique.

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Presented at the Symposium on Trace Characterization-Chemical and Physical, October 5, 1966, Gaithersberg, Maryland, U. S. A.     

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.     

Rapid titrimetric determination of microgram amounts of fluoride ion with spadns -thorium lake

A rapid titrimetric method has been developed for the determination of microgram amounts of fluoride ion in the range from Img-Ioomg, in 50 ml final volume. It involves the adjustment of pH, addition of 1 ml of 0.02% SPADNS indicator, dilution to volume and titration with standard 0.004M Th(NO₃)₄ until the colour obtained matches a blank containing the buffered solution of the indicator with a. trace of thorium nitrate solution. Interference by various ions was also studied. The method described for the determination of fluoride ion is very rapid and the colour change at the end point being sharp, the detection of the end point is very easy. The method is applicable to pure solutions of fluondes.     

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.     

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.