Triazene-N-oxides as new type of fluorimetric reagents

Summary The fact that niobium gives orange fluorescence ( _ex ^max 570, _em ^max 540 nm) in both acid and alkali media with 3-(2-hydroxyphenyl)-1-phenyltriazene-N-oxide, has been exploited to develop a simple, sensitive and selective method for the determination of trace amounts of the metal in 50% ethanolic medium. Measurements are made at the pH range of 3.2–5.0. Fluorescence intensity attains the maximum value after 45 min of standing and remains almost unchanged after 24 h. Calibration graph maintains linearity from 50 ppb to 2.2 ppm of the metal. Forty cations and anions are without any effect on the fluorimetric determination of niobium(V). The method has been applied to the analysis of synthetic mixtures.     

Polarographic determination of zirconium at trace level

An indirect polarographic method has been developed for the determination of zirconium by formation of molybdozirconophosphoric acid, its extraction with MIBK or a mixture of diethyl ether and 1-butanol, stripping with alkali and measurement of the Mo(VI) by its catalytic effect on the polarographic reduction of hydrogen peroxide. Depending on the extradant, a detection limit of 2.5 or 8.9 mu/gl, can be achieved.     

An automated fluorimetric method for the determination of nanogram quantities of selenium

An automated solvent extraction method, based on the fluorescence of 4,5-benzopiazselenol has been developed for the determination of nanogram quantities of selenium. Sample extracts, analysed at a rate of 40 per hour, gave standard deviations of 0.022, 0.054, 0.096 ng g^-1 at levels of 1, 5 and 10 ng g^-1 respectively. The detection limit was therefore approximately 0.044 ng g^-1. Of the more common ions at 1 mM concentration, only palladiuim(II) and tin(IV) caused appreciable interference in the presence of oxalate or ethylenediaminetetraacetic acid.     

Selective kinetic fluorimetric determination of copper at the ng ml level

A kinetic fluorimetric method for copper, based on a previously described system with 1,1,3-tricyano-2-amino-1-propene as reagent, has been developed. It has been shown that the determination is based on copper-catalysed oxidation of the reagent rather than on complex formation with it, although complex-formation with imidazole seems needed to stabilize the copper(I) that is thought to be the catalyst. The application of several kinetic methods (tangent, fixed-time and variable-time) allows determination of very low concentrations of copper (1-35 ng ml ) with a sensitivity about 100 times that of an earlier method. Of 47 ions tested, only EDTA interfered when present at the same concentration as copper. The method has been applied to the determination of copper in blood serum samples.     

协同催化荧光法测定痕量钴的研究

基于在硼酸 硼砂介质中,钴和三乙醇胺协同催化过氧化氢氧化还原型罗丹明6G的反应,建立了协同催化荧光法测定痕量钴的新方法。钴的检出限为0.011ng/mL;测定范围0.016～0.80ng/mL。方法已用于小麦粉,玉米粉,VB12和人尿液等样品中痕量钴的测定。     

基于痕量联苯胺阻尼作用的荧光光度分析

在HCl介质中，联苯胺的存在对KBrO3氧化吡咯红反应有抑制作用，据此建立了测定痕量联苯胺的荧光动力学新方法。对方法的介质条件、试剂用量、干扰物质影响进行了系统研究。在最佳实验条件下，方法的线性范围为30～400ng／mL，检出限为14．4ng／mL，对11份浓度为80ng／mL，300ng／mL的联苯胺标准溶液进行平行测定，相对标准偏差分别为2．1％和1．2％。本法用于塑料和雨水中联苯胺的测定，回收率为97．8％～102．1％。     

Rapid determination of uranium at the nanogram level in geological and biological materials

A rapid method for the determination of uranium at nanogram levels in geological and biological materials is described. The method is based on the separation of 23.5 min²³⁹U, produced on neutron activation, by solvent extraction with TBP from nitric acid medium in the presence of HF, which prevents interference from Th; a number of other possibly interfering elements were shown to be negligibly extracted. The method is selective and sensitive enough for the determination of nanogram levels of uranium in soils, ores and biological samples. Results for some standard reference materials were in good agreement with certified values. Presented at the International Conference on Analytical Chemistry, Interan '76, Prague, August 1976.     

Mandelic acid and halogen-substituted mandelic acids as reagents for the determination of zirconium

o-, m-, and p-Fluoro- and -trifluoromethylmandelic acids have been prepared and an assessment made of their value as précipitants for zirconium. Though the p-derivatives are satisfactory there are no obvious advantages in their use. Direct weighings of zirconium mandelate and p-bromomandelate, about which there have been conflicting reports in the literature, have been investigated also. P-Bromomandelic acid has been used successfully for the determination of amounts of zirconium oxide between 3 and 50 mg per 100 ml but ignition of the precipitate to zirconium oxide is necessary. Of the acids examined, mandelic itself gives the only precipitate which is almost constant and stoichiometric in composition. The composition of this compound, however, varies slightly with the amount of zirconium present in the solution under test, and though an overall empirical factor can be applied its use is recommended only if a high order of accuracy is not required. If a series of determinations in a narrow range is to be carried out by direct weighing of zirconium mandelate, more accurate results might be obtained by determination of the appropriate factor for that range.     

Kinetic fluorimetric determination of organic peroxides and lipohydroperoxides at the nanomole level

A new kinetic fluorimetric method for determination of cumene hydroperoxide, tert-butyl hydroperoxide and lipohydroperoxides is reported. It is based on the manganese(II)-catalysed oxidation of 2-hydroxynaphthaldehyde thiosemicarbazone (HNTS) by a hydroperoxide. Measurements are made by the initial-rate method, which allows determination of as little as 0.1 nmole of peroxide and also permits establishment of the differences in reactivity between the hydroperoxides assayed. The method has been applied to the determination of lipohydroperoxides in six commercial oil samples (grape, corn, sunflower seed, cod-liver and linseed). The results obtained can be expressed as meq of peroxide per kg of oil, and are in close agreement with those obtained by the classical iodometric method.     

Kinetic fluorimetric determination of aminoglycoside antibiotics by use of OPA and N-acetylcysteine as reagents

The use of N-acetylcysteine for the kinetic fluorimetric determination of aminoglycoside antibiotics by reaction with o-phthaldialdehyde (OPA) in a basic medium was studied. The results obtained show that this thiol is a satisfactory substitute for 2-mercaptoethanol as reagent for the formation of isoindole derivatives of compounds containing primary amines such as amikacin, kanamicin and tobramycin, while avoiding its unpleasant odour. Due to the fast formation of the fluorescent derivatives the stopped-flow mixing technique must be used in order to acquire analytical kinetic data. This allowed the development of a kinetic automatic method for the determination of amikacin applicable to routine analyses. The initial rate was measured within ca. 5 s and the calibration graph was linear over the range 0.05–30.0 g mL^–1. The method was satisfactorily applied to the determination of amikacin in two pharmaceutical preparations with a mean recovery of 98.7%.     

动力学荧光法分析痕量碘的研究

基于在磷酸介质中，碘能催化过碘酸钾氧化罗丹明6G的反应，使荧光猝灭，建立了催化荧光法测定痕量碘的新方法。方法的检出限为0．019mg/L，线性范围为0．020mg/L-0.80mg/L，可直接用于加碘食盐、海带、紫菜和盐酸胺碘酮药片中碘的测定。     

Study on catalytic fluorimetric determination of trace manganese

A new kinetic fluorimetric method has been proposed for the determination of trace manganese. The method is based on the catalytic oxidation of rhodamine 6G with potassium periodate in the presence of nitrilo triacetic acid as activator, in near neutral media. The detection limit for manganese is 0.018 ng/ml. The linear range of the determination is 0.04-1.00 ng/ml. The proposed method suffers from few interferences in the presence of more than 30 foreign ions. The method has been used to determine trace manganese in hair, urine, fish and water samples. The results are satisfactory.     

Radiochemical neutron activation analysis in standardization of trace elements in biological reference materials at the nanogram level

Summary Results for up to 12 trace elements in some newer biological materials of the NBS Washington (Citrus Leaves, New Bovine Liver, Wheat and Rice Flours, Milk Powder, Stabilized Wine) are reported using radiochemical neutron activation analysis. A discussion of the techniques and problems of standardization and the correct use of standards is included.

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Radiochemische Neutronen-Aktivierungs-Analyse zur Standardisierung von Spurenelementen in biologischen Referenzproben in ng-Mengen

Zusammenfassung Ergebnisse für bis zu 12 Spurenelemente in einigen neuen biologischen Proben des NBS, Washington, (Citrus-Laub, frische Rindsleber, Weizenund Reismehl, Milchpulver, Wein) wurden mitgeteilt, die mittels radiochemischer Neutronen-Aktivierungs-Analyse erhalten wurden. Eine Diskussion der Verfahren, der Probleme der Standardisierung sowie der korrekten Verwendung der Standardproben wurde geboten.

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Presented in part at the 9th International Symposium on Microchemical Techniques, Amsterdam, August 1983.     

Simultaneous polarographic determination of adenosine-5'-monophosphate and adenosine-5'-0-monothiophosphate at the nanogram level.

A method is described for the simultaneous gas Chromatographie determination of arsenic, germanium and antimony. The approach is based on conversion of the elements to their hydrides, collection of these via a semi-selective trapping procedure, desorption from the trap, and delivery to a gas Chromatograph for separation and determination. Detection limits, based on the analysis of 100-ml natural water samples, are 1, 0.3, and 10 μg l^-1 for As, Ge, and Sb, respectively. Recovery studies indicate that the relatively simple method yields precise and accurate results.     

Kinetic method for the determination of mercury at the nanogram level using an iodide-catalyzed arsenitecerium reaction

Summary A kinetic method for the determination of mercury has been developed by using the iodide-catalyzed reaction between arsenite (III) and cerium (IV). The difference in reaction rate due to inhibition by mercury was measured spectrophotometrically at 275 nm. Optimum reaction conditions were investigated in order to obtain a greater sensitivity in the determination of mercury. The described procedure can be used satisfactorily for samples containing mercury in the 1 to 60 ng range, with an overall error of less than 5 %.

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Zusammenfassung Eine kinetische Methode zur Quecksilberbestimmung mit Hilfe der jodkatalysierten Reaktion zwischen Arsenit und Cer(IV) wurde ausgearbeitet. Der infolge der Hemmung durch Quecksilber eintretende Unterschied im Reaktionsablauf wurde spektrophotometrisch bei 275 nm gemessen. Die optimalen Reaktionsbedingungen wurden untersucht, um größere Empfindlichkeit bei der Quecksilberbestimmung zu erzielen. Die beschriebene Arbeitsweise kann mit zufriedenstellendem Erfolg für Proben angewendet werden, die 1–60 ng Hg enthalten. Der Fehler ist durchwegs geringer als 5%.

     

Spectrophotometric determination of zinc at trace level in environmental samples

Summary Zinc is selectively extracted with N-hydroxy-N,N-diphenylbenzamidine and spectrophotometrically determined with 4-(2-pyridylazo)resorcinol. The molar absorptivity is 9.4×10⁴l·mol^–1 cm^–1. Relative standard deviation is ±1.5%.     

High-performance liquid chromatographic determination of humic acid in environmental samples at the nanogram level using fluorescence detection

A high-performance liquid chromatographic method for the determination of humic acid in environmental samples is presented. The humic acid is chromatographed as its sodium or calcium complex, eluting as a single, sharp peak. Coral skeletal matter, sea water, river water, soils and plant matter were successfully analysed. The detection limit is 15 ng. The relative standard deviation for a coral skeletal sample is 1.9%. Unusual chromatographic properties such as the occurrence of peak broadening with increased concentration appear to be due to a slow change in the equilibrium composition of humic acid. In solution, fulvic acid showed similar properties to humic acid.     

Dapsone and iminodibenzyl as novel reagents for the spectrophotometric determination of trace amounts of nitrite in water samples.

A rapid, simple, sensitive and selective spectrophotometric determination of nitrite using new diazotizing and coupling reagents is described. The method is based on a diazotization-coupling reaction between dapsone and iminodibenzyl in a hydrochloric acid medium. The molar absorptivity and Sandell's sensitivity were found to be 7.5 x 10(4) l mol(-1) cm(-1) and 0.000613 microg ml(-1), respectively. The interference effects of various cations and anions were also studied and reported. This method has been found to be applicable for the determination of nitrite in various water samples.     

Evaluation of long chain dithiocarbamates as photometric reagents for the determination of trace amounts of uranium

A highly sensitive extractive spectrophotometric method for the determination of U(VI) using octadecyldithiocarbamate (ODDTC) has been developed. The efficiency of ODDTC as a chelating agent is compared with that of hexadecyl, tetradecyl and dodecyl dithiocarbamates. U(VI) reacts with these dithiocarbamates in ethanol to form reddish-brown water-insoluble chelates capable of being extracted into CHCl₃. The molar absorptivities range from 1.16·10 to 4.91·10⁴l·mol^–1·cm^–1, the highest value being found for ODDTC. Suitable conditions for the extraction and the effect of foreign ions were investigated. The method can be used for the determination of trace amounts of U(VI) in water and sand. The results are comparable to ICP-AES method.     

An extractive pellet fluorimetric determination of trace uranium in thorium rich samples

An extractive pellet fluorimetry determination of trace uranium in thorium rich samples has been developed. This is based upon a solvent extraction system which completely separates both the elements uranium and thorium from each other. Thorium as a neutral complex with 2,3-dihydroxynaphthalene at pH 4–6 is extracted into ethylacetate and then uranium-2,3-dihydroxynaphthalene anionic complex is extracted into another batch of ethylacetate at pH 11–12 under the influence of a counter cation, cetyltrimethylammonium ion. This method has been applied for the determination of trace uranium in synthetic nuclear grade thorium oxide and thorium rich mineralized rock with high degree of accuracy and precision.