Liquid-liquid extraction of ferric thiocyanate with hexamethyl phosphoramide: Direct spectrophotometric determination in the organic phase

Summary Application of hexamethylphosphoramide (HMPA) in the iron(III)-thiocyanate system gives a simple, sensitive and highly selective method for the spectrophotometric determination of Fe(III) in the organic phase (CHCl₃). The color is stable for more than 24 hours in CHCl₃. The system obeys Beer's law for 7g Fe/ml and the optimum concentration range is found to be 0.5–5g/ml. The molar absorptivity of 1.33×10⁴ l·mole^–1·cm^–1, and Sandell's sensitivity is 0.0044/cm² at 460 nm The composition of Fe(III) to thiocyanate is found to be 13 in the presence of HMPA in CHCl₃. The method is free from interferences of many anions and cations. The method has been used to determine iron in bauxite ore.

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Flüssig-flüssig-Extraktion von Eisenrhodanid nach Zusatz von Hexatnethyl-pbosphoramid: Direkte spektrophotometrische Bestimmung in der organischen Phase

Zusammenfassung Der Zusatz von Hexamethylphosphoramid (HMPA) zu Eisen(III)-Thiocyanat führt zu einer einfachen, empfindlichen und sehr selektiven Methode der spektrophotometrischen Bestimmung von Fe(III) in organischer Phase (CHCl₃). Die Farbe bleibt in Chloroform mehr als 24 Stunden beständig. Das System entspricht dem Beerschen Gesetz unterhalb 7g Fe/ml. Das Konzentrationsoptimum liegt zwischen 0,5 und 5g/ml. Die molare Extinktion beträgt 1,33·10⁴ l·Mol^–1·cm^–1, die Empfindlichkeit nach Sandell 0,0044g/cm² bei 460 nm. Das Verhältnis Fe(III): Rhodanid in CHCl₃ ist 13 in Gegenwart von HMPA. Die Methode wird von vielen Anionen und Kationen nicht gestört. Sie wurde zur Bestimmung von Eisen in Bauxit verwendet.

     

Nicotinamidoxime as an analytical reagent

Summary Cobalt(II) gives a deep blue colour with nicotinamidoxime in alkaline aqueous-ethylalcoholic medium which has been used with advantage for the spectrophotometric determination of this metal. The optimum p_H for the development of colour is 9.8–11.3 in aqueous-alcoholic (40% v./v.) medium in presence of a large excess of the reagent, at 15–40°C. The colour intensity is measured at 580 m,. Sensitivity is 0.01 g cobalt per cm², while visual identification limit is 0.5 g cobalt per ml (12·10⁶). Beer's law is obeyed in the range of 0.2–20 ppm of the metal, with an optimum range of 2–16 ppm. The colour is stable for about half an hour in the p_N range of 9.8–11.3 and at least one hour in the range of 10.5 to 11.0. On account of the high p_N and alcoholic medium used, most of the cations and anions interfere and, hence, must be removed.Part I: See Z. anal. Chem. 168, 326 (1959).     

Trace element analysis of some shaving powders commonly marketed in Nigeria using instrumental neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been employed viak ₀ approximation method to determine elemental composition of five shaving powders commonly marketed in Nigeria. Fe displayed the highest concentrations in the range 1000–2000 g·g^–1. Na and Zn concentrations were established in the range 200–400 g·g^–1. Heavy elements like Ga, La, Cr, Co, Ag, Ce and Nd concentrations were noted in the lower range of 1–10 g·g^–1 Br, As, Sb, Sm, Eu, W, Cs, Tb, Yb, Hf, Ta, Th and U concentrations were established in even lower traces in the <1 g·g^–1 range. Results obtained for a certified reference material, CANMET BL-1 and CERT (in house) Kaolin standard compared favourably with the literature values thus establishing the results presented for the shaving powders.     

Spectrophotometric Determination of Iron(III) After Separation by Adsorption of its 2-Thenoyltrifluoroacetone Complex on Microcrystalline Naphthalene

Summary A new spectrophotometric method for the determination of iron (III) after adsorption of its red TTA complex onto microcrystalline naphthalene has been developed. Iron(III) reacts with 2-thenoyltri-fluoroacetone in pH range 2.4–5.2 to form a water-insoluble 13 red complex which is easily adsorbed onto microcrystalline naphthalene from its acetone solution. The naphthalene mixture is separated, dried and dissolved in 10 ml dioxane. The red organic phase has a plateau around 480–500 nm while the reagent has no absorbance beyond 420 nm. The system obeys Beer's law over 20–120g iron(III) in 10 ml of dioxane solution or 0.4–2.4 ppm aqueous. The molar absorptivity of the complex species is 3.9×10³·l·mol^–1·cm^–1, while the sensitivity for Fe(III) extends to 1.43×10^–2 g cm^–2 for 0.001 absorbance. Samples containing 80g of iron gave a relative standard deviation of 1.23%. The effects of experimental variables such as pH, amount of reagents, shaking and digestion time, aqueous volume and diverse ions have been examined. The method has been applied to the determination of iron(III) in standard reference and environmental samples and results compared with other standard colorimetric procedures.

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Spektrophotometrische Bestimmung von Eisen(III) nach Adsorption seines 2-Thenoyltrifluoraceton-Komplexes an mikrokristallines Naphthalin

Zusammenfassung Eine neue spektrophotometrische Methode zur Bestimmung von Eisen (III) nach Adsorption seines roten TTA-Komplexes an mikrokristallines Naphthalin wurde ausgearbeitet. Fe(III) reagiert mit 2-Thenoyltrifluoraceton bei pH 2,4-5,2 unter Bildung eines roten, wasser-unlöslichen 13-Komplexes, der sich aus seiner acetonischen Lösung leicht an mikrokristallines Naphthalin adsorbieren läßt. Das Naphthalin-Gemisch wird abgetrennt, getrocknet und in 10 ml Dioxan gelöst. Die rote organische Phase hat ein Adsorptions-Plateau bei 480–500 nm, während das Reagens jenseits 420 nm nicht adsorbiert. Das System entspricht dem Beerschen Gesetz von 20–120g Fe(III) in 10 ml Dioxan-Lösung bzw. 0,4–2,4 ppm in wäßriger Lösung. Die molare Extinktion der Komplexverbindung beträgt 3,9× 10³l·mol^–1·cm^–1. Die Empfindlichkeit für Fe(III) entspricht 1,43×10^–2 g cm^–2 für 0,001 Absorptionseinheiten. Proben mit 80g Fe(III) zeigen eine rel. Standardabweichung von 1,23%. Die Wirkung variabler Versuchsbedingungen pH, Reagensmenge, Zeit, Volumen und diverse Fremdionen wurden geprüft. Das Verfahren wurde an Standardsubstanzen geprüft und seine Ergebnisse mit denen anderer kolorimetrischer Verfahren verglichen.

     

Liquid Chromatographic Determination of Glutamine in Cerebrospinal Fluid Using 2-Hydroxynaphthaldehyde Derivatizing Reagent

Summary An analytical procedure has been developed for the selective determination of glutamine from cerebrospinal fluid (CSF) using 2-hydroxynaphthaldehyde derivatizing reagent. Arginine and tyramine could also be determined simultaneously. Separation was on a Phenomenex C-18, (150 × 4.6 mm i.d.) column with methanol: water (63:38 v/v) mobile phase at 1mL min^–1 and UV detection at 330nm. Detection limits for glutamine, arginine, and tyramine were 2.8 ng, 17.4 ng and 3.45 ng injection^–1 (5 L), respectively. A large number of amines and amino acids eluted did not affect the determination of glutamine. The analysis of CSF of four patients suffering from hydrocephalus for glutamine indicated concentrations within range 37.4–11.24 g mL^–1 with coefficient of variation 3.0–6.2%.     

Bestimmung flüchtiger organischer Verbindungen in atmosphärischen Aerosolproben durch thermische Desorption und FID-Detektion

Zusammenfassung Staub- und Aerosolproben werden im Stickstoffstrom im Temperaturbereich 25–420° C einer temperaturprogrammierten thermischen Desorption unterworfen. Die flüchtigen organischen Komponenten werden mittels FID summarisch als volatile organic carbon (VOC) bestimmt. Die Eichung des Analysators erfolgt durch ein Aliphaten-Standardgemisch. Bei Probemengen von 50–100g Aerosol ist eine Bestimmung des VOC-Gehaltes mit einer Reproduzierbarkeit vons=3,5–7 rel.% möglich. Die Nachweisgrenze der Methode liegt für Aerosolproben bei 0,3g VOC.

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Determination of volatile organic components in atmospheric aerosol samples by thermal desorption and FID-detection

Summary Atmospheric dust and aerosol samples are treated in a nitrogen carrier gas stream at the temperature range 25–420° C by temperature programmed desorption. The volatile organic components are detected by FID. Calibration of the analyzer is carried out with a standard mixture of aliphatic hydrocarbons. The result is expressed as volatile organic carbon (VOC). The reproducibility of the method for aerosol samples (sample weight 50–100g) is in the range of 3,5–7% r. s. d. The detection limit of the method is 0,3g VOC.

     

Chemical composition of T-21 silica tubing and implications for neutron activation analysis

T-21 silica, a commonly used encapsulation material in neutron activation analysis of small samples, was analyzed by INAA to determine trace levels of the following impurities: Na, Sc, Cr, Fe, Co, Ni, Zn, Br, Sb, La, Ce, Sm, Tb, Hf and Au. In the unprocessed form supplied by the manufacturer, pieces of T-21 weighing 50 mg contain 6·10^–2 g Na; 9·10^–3 g Fe; 3·10^–7–7·10^–6 g light REE, Sc and Hf and 4·10^–8 g Tb and Au. In a series of glass-blowing steps, in which unfiltered gases were used for fuel, and cleaning steps, in which reagent grade aqua regia was used, irradiation vials were produced which contain higher average levels of Sc, La, Sm, Tb and Hf, by factors ranging from 1.3 for Sm to 11.5 for La, and lower average levels of Co, Na and Fe, by factors of 1.4, 2.0 and 4.0, respectively, than the unprocessed material. These contamination levels lead to blank corrections of 21% for La, 2.6% for Ce and 3.0% for Hf in 40 g samples of refractory inclusions from carbonaceous chondrites, if counted in their irradiation vials.     

Titrimetry in a continuous flow system

Summary Sulphate in the range of 5–2000 mol · l^–1 is automatically titrated with Ba(II) in a device with an optical detection which is able to correct automatically for dilution and turbidities. The flow-through system contains 80% v/v ethanol; the indicator is dimethyl sulfonazo(III). Above a concentration level of about 20 mol · l^–1 SO ₄ ^2– the standard deviation is less than 5% rel. The titration time is negligibly small as compared to the sampling time.

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Titrimetrie im DurchflußsystemI. Apparatur und Sulfatbestimmung

Zusammenfassung Sulfat wird im Bereich von 5–2000 mol · l^–1 automatisch mit Ba(II) mit einem Gerät mit optischer Detektion titriert, das automatisch für Verdünnung und Trübung korrigieren kann. Das Durchflußsystem enthält 80% v/v Äthanol; Indicator ist Dimethylsulfonazo(III). Die Standardabweichung für Proben mit einem Sulfatgehalt höher als 20 mol · l^–1 ist niedriger als 5% rel. Die Titrationsdauer ist vernachlässigbar im Vergleich mit der Zeit für die Probennahme.

     

Liquid-liquid extraction of ruthenium(III) thiocyanate with hexamethylphosphoramide: Direct spectrophotometric determination in the organic phase

Summary Ru(III)-thiocyanate has been extracted with hexamethylphosphoramide (HMPA) in methyl isobutyl ketone (MIBK). Thus the extractability, sensitivity and selectivity are improved over the simple binary Ru(III) thiocyanate system in spectrophotometric determination of ruthenium in the organic phase. The maximum colour develops on the steam bath, at the acidity range of 1.5–2.5M with HCl and ammonium thiocyanate concentration range of 0.25–0.5M. The colour is completely extractable in MIBK when 1.5–3.0 ml HMPA is used and show maximum absorbance at 570 nm. The colour system obeys Beer's law for 0.7–13 g Ru/ml and the optimum concentration range is 2–13 g/ml. The molar absorptivity and sensitivity are 69401-mole^–1 cm^–1 and 0.0145 g/cm² respectively. The percent relative error is 2.72%. The method is very simple and does not require oxidation and subsequent distillation. The method can be applied in the presence of osmium.

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Flüssig-flüssig-Extraktion von Ruthenium(III)thiocyanat mit Hexamethylpbosphoratnid: spektrophotometrische Bestimmung in der organischen Phase

Zusammenfassung Ru(III)thiocyanat wurde mit Hexamethylphosphoramid (HMPA) in Methylisobutylketon (MIBK) extrahiert. Die Extrahierbarkeit, Empfindlichkeit und Selektivität wurden im Vergleich zum binären Ru(III)-thiocyanatsystem durch spektrophotometrische Bestimmung in der organischen Phase verbessert. Das Farbmaximum entwickelt sich auf dem Wasserbad in 1,5 bis 2,5M Salzsäure bei einer Ammoniumthiocyanat-Konzentration von 0,25–0,5 Mol/l. Mit 1,5–3,0 ml HMPA läßt sich die Färbung vollständig in MIBK extrahieren und zeigt ein Absorptionsmaximum bei 570 nm. Die gefärbte Lösung entspricht dem Beerschen Gesetz für 0,7–13 g Ru/ml; das Konzentrationsoptimum liegt zwischen 2 und 13 g/ml Die molare Absorptivität und Empfindlichkeit betragen 69401·mol^–1·cm^–1 bzw. 0,0145g/cm². Die Methode ist sehr empfindlich; Oxydation und nachfolgende Destillation sind überflüssig. Bei Anwesenheit von Osmium ist dieses vorher zu entfernen.

     

Photometrische Bestimmung von Arsen und Phosphor in hochreinen Chemikalien

Zusammenfassung Optimale Bedingungen zur photometrischen Bestimmung von Spurengehalten Arsen und Phosphor nebeneinander wurden ermittelt. Die dem Verfahren zugrundeliegende Farbreaktion ist die Umsetzung von in saurer Lösung gebildeter Dodekamolybdatoarsen- bzw.-phosphorsäure mit Hydraziniumsulfat zu Arsen-bzw. Phosphor-Molybdänblau. Auf diese Weise sind Arsengehalte zwischen 1,1 und 10,0 g sowie 0,12 bis 8,0 g Phosphor zu bestimmen. Die Empfindlichkeit der Verfahren beträgt ₈₃₀=2,0·10⁴l·mol^–1·cm^–1 für As und ₈₃₀=2.6·10⁴ l·mol^–1·cm^–1 für P.Die Bestimmung beider Elemente nebeneinander gelingt dadurch, daß man nach der Summenbestimmung von As und P das Arsen aus der Analysenlösung durch Verflüchtigung als AsBr₃ entfernt oder es zu nicht mehr reaktionsfähigem As(III) reduziert. In der nun As-freien Lösung kann der P-Gehalt nach gleichem Verfahren ermittelt werden.Das Verfahren wurde zur Bestimmung von Arsen und Phosphor in hochreinen Chemikalien eingesetzt.

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Photometric determination of arsenic and phosphorus in high-purity chemicals

Summary Optimal conditions for the photometric determination of microgram amounts of arsenic and phosphorus are reported. The method bases on the reaction between molybdophosphoric or molybdoarsenic acid respectively, and hydrazinium sulphate to provide heteropoly blue.In this way arsenic can be determined within a range from 1.1 to 10.0 g and phosphorus within a range from 0.12 to 8.0 g. The absorptivities are ₈₃₀=2.0·10⁴l·mol^–1 ·cm^–1 for As and ₈₃₀=2.6·10⁴l·mol·cm^–1 for P, respectively.The simultaneous determination of As and P involves at first the determination of the sum of these elements and after reduction of arsenic to As(III) or volatilization as the bromide in a second step the determination of P in the same way.The method has been applied to the determination of arsenic and phosphorus in high-purity chemicals.

     

Extraction and spectrophotometric determination of uranium(VI) withN-phenylcinnamohydroxamic acid

Uranium(VI) reacts withN-phenylcinnamohydroxamic acid to form an orange-yellow complex in the pH range 5.5–8.5. The orange-yellow complex, having the composition of 12 (metal:ligand), is quantitatively extractable into ethyl acetate. The spectrum of the complex exhibits a maximum absorption at 400 nm with a molar absorptivity of 6500 M^–1·cm^–1. The coloured system obeys Beer's law in the concentration range 2–40g·ml^–1 of uranium(VI). The photometric sensitivity of the colour reaction is 0.037 g·cm^–2 of uranium(VI). Most of the common ions do not interfere and the method has been found to be simple, precise, and free from the rigid control of experimental conditions. The method has been applied to the determination of uranium in synthetic matrices and potable water.     

Catalytic-fluorimetric determination of EDTA and iron(III) by flow injection analysis

Summary In this paper the authors report on several methods for the direct determination of EDTA and indirect determination of iron(III), based on the inhibition effect of EDTA on the catalytic action of copper (II) on the oxidation of 2,2-dipyridyl ketone hydrazone by hydrogen peroxide and on the decrease of this inhibition effect in the presence of Fe(III), respectively. These methods allow the determination of EDTA in the ranges of 0.4–2.0 g · ml^–1 and 0.2–1.0 g · ml^–1 for the normal and reversed FIA modes, respectively, and of 40–240 ng · ml^–1 for Fe(III) by reversed FIA.

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Katalytisch-fluorimetrische Bestimmung von EDTA und Eisen(III) durch FließinjektionsanalyseInhibitionsmethoden

Zusammenfassung Verfahren zur direkten Bestimmung von EDTA sowie zur indirekten Bestimmung von Eisen(III) werden beschrieben. Sie beruhen auf der Inhibitorwirkung von EDTA auf den katalytischen Effekt von Kupfer(II) bei der Oxidation von 2,2-Dipyridylketonhydrazon mit Wasserstoffperoxid bzw. auf der Schwächung dieser Inhibitorwirkung in Gegenwart von Eisen(III). Es ist mit diesen Methoden möglich, EDTA im Bereich von 0,4–2,0 g/ml (normale FIA) bzw. 0,2–1,0 g/ml (umgekehrte FIA) und Eisen im Bereich von 40–240 ng/ml (umgekehrte FIA) zu bestimmen.

     

Photometrische Bestimmung von Bor in hochreinen Chemikalien

Zusammenfassung Bor reagiert in Form des Tetrafluoroboratkomplexes mit dem basischen Farbstoff Methylenblau unter Bildung eines mit 1,2-Dichlorethan extrahierbaren Ionenassoziatkomplexes. Die optimalen Bedingungen für die photometrische Bestimmung von Mikromengen Bor werden ermittelt und das vorgestellte Verfahren hinsichtlich Empfindlichkeit, Genauigkeit und kleinster bestimmbarer Menge charakterisiert.Die Borbestimmung ist im Bereich von 0,25–2,5 g Bor mit einer relativen Standardabweichung von 3,8% für 1,0 g Bor möglich. Der molare Extinktionskoeffizient beträgt ₆₆₅=8,2·10⁴1·mol^–1·cm^–1, die Nachweisgrenze nach Kaiser 0,125 g Bor.Das Verfahren wurde zur Bestimmung von 10^–6 bis 10^–5% Bor in folgenden hochreinen Chemikalien eingesetzt: Methanol, Ethanol, Isopropanol, Aceton, Mineralsäuren, Essigsäure, Ammoniak und Wasserstoffperoxid.

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Photometric determination of boron in high-purity chemicals

Summary Boron reacts with fluoride to form borofluoride which itself reacts with the basic dye methylene blue forming a complex which can be extracted into 1,2-dichloroethane. Optimum conditions were established for the determination of microamounts of boron by an extraction-photometric method. The procedure presented has been characterized with regard to sensitivity, precision and detection limit.Boron can be determined within a range from 0.25 to 2.5 g with a relative standard deviation s _rel=3.8% for 1 g B. The absorptivity is ₆₆₅=8.2·10⁴1·mol^–1·cm^–1, the detection limit according to Kaiser was found to be 0.125 g B.The procedure was used to analyse high-purity chemicals (10^–6–10^–5% B) such as organic solvents, mineral acids, acetic acid, ammonia, hydrogen peroxide etc.

     

Di-μ-hydroxo bridge-cleavage reactions between [Co(nta)(μ-OH)]2 2− and different monodentate ligands

The cleavage of the di--hydroxo bridges of [Co(nta)(-OH)]₂ ^2– by dimethylaminopyridine (dmap) and pyridine (py) has been investigated. [Co(nta)(-OH)]₂ ^2– equilibrates rapidly in aqueous basic solutions with a mono--hydroxo bridged Co^III species [pK _OH = 3.26(2)] and both these species react with the incoming ligand to form different ion associated species which react in the subsequent rate-determining steps (k ₁ and k ₂) to form presumably a ligand-substituted, mono-bridged species, [(nta)(OH)Co--OH-Co(nta)(L)]^2–. Values for k ₂, the preferred mono--hydroxo bridged substitution pathway for these reactions, vary between 6.8(2) × 10^–4 s^–1 (py) and 8.5(4) × 10^–2 s^–1 (dmap).     

Path of “dry” electrons before localization in liquid hydrocarbons

Conclusions On the basis of measurements of values of in liquid hydrocarbons, it has been shown that the path length before localization of a photoliberated electron increases with increasing mobility of the excess electron, from approximately 40 Å (methylcyclohexane) to 200 Å (isooctane). In a liquid with10^–2 cm²/V·sec (methylcyclohexane, hexane), the localization takes place before or immediately after thermalization of the electron. In a liquid with>10^–1 cm²/V·sec, the electron passes through the main part of its path before localization, being in thermal equilibrium with the medium.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2198–2203, October, 1985.     

Semi-automatic catalytic titration of some aminopoly-carboxylic acids,copper(II), and cobalt(II)

Summary A semi-automatic potentiometric method is described for the catalytic titrimetric determination ofg amounts of some aminopolycarboxylic acids. The method is based on their inhibitory effect on the copper(II)-catalyzed periodate-thiosulfate reaction. Amounts of EDTA in the 0.7–600g range (10^–6–8×10^–5 M), of DCTA in the 7–7000g range (10^–6–10^–3 M), of EGTA in the 0.8–800g range (10^–7–10^–4 M), and of DTPA in the 4–800g range (5×10^–7–10^–4 M) were determined with average relative errors and coefficient of variation of about 0.4–1%. The method has also been used for the indirect catalytic titrimetric determination ofg amounts of Cu²⁺ and Co²⁺ ions with about the before mentioned accuracy and precision.

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Halbautomatische katalytische Titration einiger Aminopolycarbonsäuren sowie von Cu(II) und Co(II)

Zusammenfassung Eine halbautomatische potentiometrische Methode zur katalytischen Maßanalyse von Mikrogrammengen einiger Aminopolycarbonsäuren wurde angegeben. Sie beruht auf dem Hinderungseffekt gegenüber der Cu(II)katalysierten Perjodat-Thiosulfatreaktion. EDTA in Mengen von 0,7–600g, DCTA in Mengen von 7–7000g, EGTA in Mengen von 0,8–800g und DTPA in Mengen von 4–800g wurden mit einem mittleren relativen Fehler von etwa 0,4–1% bestimmt. Das Verfahren wurde auch zur Bestimmung von Cu(II) und Co(II) mit der angeführten Genauigkeit verwendet.

     

Spectrophotometric determination of beryllium and zirconium using chromotrope-2C

Summary Disodium salt of o-carboxyphenylazo chromotropic acid (chromotrope 2C) has been used for the colorimetric determination of microamounts of beryllium and zirconium. The red-violet complexes show maximum absorption at 580 nm and the colour systems obey Beer's law from 0.025 to 0.375 ppm of beryllium and 2 to 12 ppm of zirconium. The optimum concentration ranges are from 0.125 to 0.375 ppm for beryllium and from 4 to 12 ppm for zirconium, where the percent relative errors per 1% absolute photometric error are, respectively, 3.014 and 3.22. The sensitivity of the reactions per cm² are 0.00067 g Be and 0.027 g Zr. The complexes, with the metal to reagent ratio of 11, have instability constants as 2.836 · 10^–6 for beryllium and 6.026 · 10^–6 for zirconium.     

Transition State Geometry and a Polar Effect in the Reactions of Peroxy Radicals with Oxygen-Containing Compounds

The reactions of structurally different peroxy radicals with the C–H bonds of oxygen-containing compounds (ketones, aldehydes, ethers, and esters) were analyzed in terms of a parabolic model. The enthalpies of these reactions and the activation energies of equienthalpic reactions of peroxy radicals with hydrocarbons were calculated, and the contribution of the polar interaction E to the activation energy was evaluated. The geometry parameters of the transition state were calculated with the use of an algorithm developed based on quantum-chemical calculations in combination with the intersecting parabolas method. It was found that the polar interaction resulted in a change in the configuration of the C···H···O reaction center in the transition state from linear to angular. A different angle (C···H···O) from 180° appeared in this case. The following linear correlation between E (kJ/mol) and cos (180° – ) was obeyed: cos (180° – ) = 1 + 6.76 × 10^–3E .     

ET-AAS in the Analysis of high-purity mercury

ET-AAS is investigated for the analysis of high purity mercury. Two possibilities are proposed: ET-AAS determination of trace analytes in the presence of high mercury concentrations or after matrix separation by reduction. The ET-AAS analysis of high-purity mercury under optimal instrumental parameters permits fast and reproducible determination of 0.03 gg^–1 Al, Cd and Mn; 0.05 gg^–1 Cu, Co, Cr, Fe, Ni and Pb and 0.2 gg^–1 V. Preliminary mercury matrix reductive separation with ascorbic acid allows determination of 0.005 gg^–1 Cd, 0.02 gg^–1 Cu, Cr and Mn, 0.03 g g^–1 Co, Ni and Pb, 0.05 g g^–1 Al and Fe and 0.1 gg^–1 V, but the reproducibility is lower. The main advantage of the second procedure is that it avoids laboratory and instrument pollution with toxic mercury.