Reduction des interferences sur la determination des metaux lourds dans les sediments de cours d'eau et les boues de stations d'epuration par spectrometrie d'absorption atomique en four graphite

(Reduction of interferences in the determination of trace heavy metals in river sediments and sewage sludges by electrothermal atomic absorption spectrometry.)The interferences of synthetic matrices of river sediments and sewage sludges in the determination of lead, copper, cadmium, chromium and nickel by electrothermal atomic absorption spectrometry were studied; Pb, Cd and Ni were the most sensitive to interferences. The effects of hydrochloric, nitric, perchloric and hydrofluoric acids were tested; perchloric acid was found to interfere most during the determinations. Hydrofluoric acid must be eliminated by evaporation. Techniques for reducing chemical interferences were evaluated. The best method was found to be matrix modification with ammonium dihydrogenphosphate and ascorbic acid for the determination of lead and nickel, and rapid heating (Max Power) for the determination of cadmium. Determinants of copper and chromium were less prone to interference.     

Quelques interferences sur le dosage du plomb dans les eaux alimentaires par spectroscopie d'absorption atomique sans flamme

Interferences in the determination of lead in potable water by graphite-furnace atomic absorption spectrometry are examined. The peak-height signal and the pyrolysis/atomization curves are studied as a function of the nature and concentration of the interferent. Some interferences are caused not by the cation or anion, but by the salt. Magnesium chloride interferes most extensively not only by decreasing the signal but also by changing the pyrolysis curve. Interferences are more pronounced in hydrochloric than in nitric acid medium. Frequently, stabilization of an interfering effect from a defined interferent concentration was observed in nitric acid medium whereas in hydrochloric acid medium the signals continued to change.     

Etude de l'application de l'isonitrosomalonylguanidine au dosage du fer dans les alliages d'aluminium et dans les zincs et au dosage du cobalt dans les aciers

Isonitrosomalonylguanidine reacts with iron salts in acid medium (pH ca. 6) ; or in basic medium (pH ca. 9), giving a blue color. This reaction is the basis of a new method for the determination of iron. in aluminium alloys (in acid medium) or in zincs (in acid medium or in basic medium) for the weakest contents. Concerning the determination of cobalt in steels, bromine can be used instead of nitric acid, in order to remove the excess of reagent.     

Sur les indicateurs d'absorption. iv

A new adsorption indicator. Red acid 6B, has been described for argentometric titrations of the halide ions.The great usefulness of the indicator lies in its being applicable for the very diluted solutions of the ions I^-.     

Extraction de l'acide oxalique par formation de paires d'ions et application au dosage de l'acide oxalique urinaireExtraction of oxalic acid by ion-pair formation with application to the determination of oxalic acid in urine

Extraction of oxalic acid by ion-pair formation with application to the determination of oxalic acid in urineThe yield of ion-pair extraction of oxalic acid by trioctylamine and triisooctylamine in chloroform depends on the pH of the aqueous phase. The optimum pH is 2.7, proving that hydrogenoxalate ion is the extractable form. Extraction yield depends on the acid used for pH adjustment and dissolution of the calcium oxalate formed in complex medium. The best results are obtained with hydrochloric and sulfuric acids and with trioctylamine extraction. This extraction was applied to oxalic acid determination by colorimetry and gas chromatography in urines from twenty healthy patients. Mean excretion was found to be $\text{0.30 mmol}\text{24 h.}$ Extraction yields lie between 94 and 106%.     

Determination de la constante d'acidite intrinseque d'un echangeur d'ions carboxylique

To obtain the intrinsic acidity constant of a carboxylic ion-exchanger, we propose a method of graphical double extrapolation. The results for an ion-exchanger made of polyvinyl alcohol grafted with acrylic acid are close to those published for the corresponding linear polyacid.     

Speciation of organotin compounds in marine sediments by capillary column gas chromatography-atomic absorption spectrometry coupled with hydride generation

A method for speciation of organotin compounds in marine sediments by solvent extraction combined with hydride generation gas chromatography-atomic absorption spectrometry has been developed. Sediment samples spiked with tributyltin and triphenyltin chlorides were homogenized in hydrochloric acid. The chlorides were extracted twice into toluene. Recoveries of the organotin compounds from the spiked sediment samples were improved by the addition of 8-quinolinol. Tributyltin and triphenyltin chlorides form ion-associates with 8-quinolinol in aqueous hydrochloric acid. The method was optimized with respect to derivatization reactions and extraction conditions. Interferences from Sn(II/IV) and additional 13 ions were investigated. Recoveries of 84-100% for tributyltin and 86-100% for triphenyltin were achieved using this method. The detection limits obtained for tributyltin and triphenyltin chlorides were 95 and 145 pg, respectively, corresponding to a relative detection limit of 95 and 145 ng kg(-1) in the sediment.     

Etude critique de la determination par spectrometrie d'absorption atomique sans flamme du selenium dans les milieux complexes apres extraction a l'aide d'o-diamines aromatiques et ajout de nickel(II)

Critical study of the graphite-furnace atomic absorption determination of selenium in biological samples after extraction with aromatic o-diamines and addition of nickel(II)A new method for the determination of traces of selenium in natural samples is proposed. After digestion with nitric, sulfuric and perchloric acids, selenium is quantitatively converted to the tetravalent state with perhydrol. Reaction with an aromatic o-diamine gives the corresponding piazselenol which can be extracted into toluene and determined by atomic absorption spectrometry after addition of nickel(II). Calibration graphs are linear in the range 0–1.5 ppm Se. A critical study shows the advantages of the method.     

The determination of arsenic in rocks,sediments and minerals by arsine generation and atomic absorption spectrometry

An arsine generation-atomic absorption method for the rapid and precise determination of 0.04–4000 p.p.m. arsenic in geological materials is described. The siliceous sample is decomposed with perchloric, nitric and hydrofluoric acids and potassium permanganate solution, and the residue is dissolved in dilute hydrochloric acid. Arsine is generated with potassium iodide, tin(II) chloride and zinc powder, and introduced to an argon—hydrogen flame. The method is applied to various standard rocks, NBS mineral standards, and geochemical exploration samples. The relative standard deviation is 4–14 %.     

Reaction des nitrones avec les chlorures d'acides: action de chlorures d'aryl-sulfonyles et du chlorure de benzoyle sur des n-oxy (aryl-1 dihydro-3,4 isoquinoleines). Formation d'une isoquinoleine,d'un isocarbostyryle ou d'une indoline selon les conditions

Toluene-p-sulphonyl chloride, p-nitrobenzoyl chloride, and benzoyl chloride react with 1-aryl 3,4-isoquinoline N-oxide depending on the acidity of the medium, the nature of the substituent at C-1, and the nature of the acid chloride, to give an isoquinoline, an isocarbostyril (resulting from migration of the phenyl substituent at C-1), an indoline (resulting from migration of the phenyl moiety incorporated in the heterocycle), or the formation of an O-acyl hydroxamic acid. The maximum selectivity is obtained in an heterogeneous medium and is governed by the intermediate formation of an hydroxylated pseudo-base.     

Determination of serum selenium by hydride generation flame atomic absorption spectrometry

Serum is rapidly digested with a mixture of nitric and perchloric acids at a temperature of 180 +/- 10 degrees C, and hydrochloric acid is used to reduce selenium(VI) to selenium(IV). Selenium is determined by hydride generation flame atomic absorption spectrometry. The results show that this method has the advantages of being sensitive, accurate, rapid and simple. After the serum is digested and diluted, 4.0 ml is taken for the determination. The characteristic concentration, detection limit, variation coefficient, recovery rate and linear range are 2.93 mug 1(-1), 1.55 mug l(-1), 1.6-5.0%, 97.3-99.2% and 0.0-320.0 mug l(-1) respectively. Serum at 4 degrees C and in frozen state can be preserved for at least 7 and 14 days, respectively.     

Le dosage de traces d'argent dans le zinc extra-pur par activation neutronique

Below the p.p.m. level, the determination of silver in zinc by non-destructive γ-spectrometry is no longer feasible due to the activation of the matrix element. The activated zinc is dissolved in nitric acid, sulfamic acid and silver carrier are added, and ^110mAg (253 d) is obtained in a radiochemically pure state after two successive electrolyses on gold cathodes.After two days of irradiation in a thermal neutron flux of the order of 3.10¹³ n/cm²/sec (BR₂-Mol), 30 ng of silver can easily be evaluated with an error of 5%. Data obtained by integral γ-counting or by γ-spectrometry are compared.     

Elimination of hydrofluoric acid interference in the determination of antimony by the hydride generation technique

For the determination of antimony by hydride generation techniques a pretreatment procedure has been developed for the reduction of Sb(V) to Sb(III) in order to remove the effect of hydrofluoric acid which strongly interferes with the reduction of pentavalent antimony to the trivalent state. It is based on the combined action of l-cysteine and boric acid at 80 degrees C. The pretreatment is effective in both nitric and hydrochloric acid media. Quantitative recoveries are obtained in less than 60 min. Under these conditions antimony is reduced to the trivalent state in acid media containing both nitric and hydrochloric acid. The method has been applied to the determination of total antimony in certified reference materials of sediments after pressurized microwave digestion with HNO(3)-HCl-HF. Good agreement is obtained by using both analytical techniques: continuous flow hydride generation atomic fluorescence spectrometry and flow injection electrothermal atomic absorption spectrometry with in-situ trapping of stibine in a graphite atomizer.     

Determination of selenium in sediments by hydride generation atomic absorption spectrometry. Elimination of interferences

Summary The hydride generation/atomic absorption spectrometry (AAS) with an automated flow system is useful for the routine analysis of selenium in environmental samples. This method is, however, subject to interferences from transition metal ions and other hydride forming ions. The conditions to minimize the interferences were established: the concentration of hydrochloric acid 6 mol/l; the concentration of tetrahydroborate 0.5%. Iron(III) chloride released the depression of selenium signals by metal ions such as copper(II) and bismuth(III). Selenium in several standard reference materials including sediment samples was determined by the present method and by fluorimetry with 2,3-diaminonaphthalene. The results obtained by the two methods agreed with an acceptable precision. This means that hydride generation/AAS offers good precision and accuracy in the determination of selenium in sediment samples as well as DAN fluorimetry. However, the former is much simpler in operation. The method was applied to the determination of selenium in estuarine sediments collected in Nagoya harbor and Ise Bay. The results can be used to assess the pollution state of these places.

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Selenbestimmung in Sedimenten durch AAS mit Hydriderzeugung. Eliminierung von Störungen

     

Enthalpies de formation du nitrate d'yttrium hexahydraté et de l'ion Y3+

The dissolution enthalpies of yttrium and hexahydrated yttrium nitrate in nitric acid at different concentrations have been measured and the following enthalpies have been determined:

     

Separation gallium-fer en presence d'edta

Macro- or microquantities of gallium can be separated from iron by precipitating the latter with sodium hydroxide in the presence of EDTA. Nearly all the gallium remains in solution. After the separation of iron, gallium is extracted with tributylphosphate from 3 N hydrochloric acid medium, and then re-extracted into water. Gallium is finally determined by precipitation with cupferron and ignition to the oxide, or for trace amounts of gallium, by colorimetric determination with rhodamine B. The method was checked with radioactive gallium and iron.     

Etude quantitative par absorption optique de l'homogeneite de monocristaux d'arseniure de gallium

The optical absorption coeffient of n-type gallium arsenide is measured at many places of samples with an infrared microscope (spot of 100 × 100 μm) and variable energies for the incident light. The inhomogeneities we observed are associated with free carrier density fluctuations in heavily doped single crystals and with the impurities diffusion around dislocations in lower ones.     

Effets polaires dans les reactions de transfert homolytique intramoleculaire d'hydrogene

In this paper we analyse the influence of a phenyl substituent on the relative rates of the 1–5 and 1–6 intramolecular hydrogen transfers. Compared to the abstraction of an aliphatic H atom, the activation energy for the abstraction of a benzylic H atom is smaller. The effect is nevertheless more important with a primary alkyl radical (1,3 kcal/mole) than with an alkoxy radical (0,9 kcal/mole. This can be analysed in terms of a polar effect. In addition, the size of the effect is too small to make a short distance transfer of a H-atom feasible; this is in keeping with the statement that H atom migration requires a linear transition state.     

Étude par spectroscopie d'absorption de la complexation des lanthanides trivalents par les acides amino-carboxyliques

An absorption spectrophotometric study of the complexation of trivalent lanthanides by aminocarboxylic acidsComplexation of the lanthanides by aminoacetic acids shows a shift in some absorption bands of the cation towards higher wavelengths. By choosing the medium —pH and concentrations —adequately, each complex species can be characterized by a certain shift. This study has been carried out at 20°C in M KCl and concerns the 1:1, 1:2, 1:3 and mixed complexes of praseodymium, holmium and thulium with G, NTA, HEDTA, EDTA, DCTA and DTPA. The characteristic shifts are correlated with the number of coordinating sites of the chelating agents. It seems that a significant change occurs in the structure of the complex when the number of coordinating sites exceeds nine for the cerium rare earths or eight for the yttrium elements.     

Sur une cause d'erreur dans le dosage par voie humide de l'azote dans les aciers speciaux

The estimation of nitrogen in normal or special steels by the Kjeldahl method can give results that are too high if the acid used to dissolve the steel (even “pro analysi” acid) contains impurities such as nitrates, and if the metal itself contains even negligible amounts of molybdenum (e g a few ten-thousandths). In this case the blank test can nevertheless give a very weak or negative result.In order to ascertain from this point of view the quality of the acid used, it is necessary to compare the nitrogen contents obtained on a sample with a very low nitrogen content, e g electrolytic iron, in the absence or in the presence, respectively, of a minute addition (about 0.1%) of molybdenum. The difference between these determinations should be negligible. If it is not, then the acid tested should be rejected, or distilled before use.