New books

Summary Micromolar analyses of the nitrogen species NH₃, NO ₂ ^– , and NO ₃ ^– in soil and other samples are usually accomplished by extracting several samples and testing each for a different species. This procedure is not viable when the quantity of the initial sample is limited. An improved method of separating and analysing for ammonia NH₃(aq), nitrite NO ₂ ^– (aq), and nitrate NO ₃ ^– (aq) from a single small sample with concentrations of 0–50 mol/l is reported. No interferences or carryovers among the three nitrogen containing species were found. Uncertainties were ±2–5 mol/l and accuracies with respect to standards were ±3 mol/l.     

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.

     

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.

     

Determination of Triphenyltin and Its Metabolite Diphenyltin in Culture Medium by High-Performance Liquid Chromatography with UV detection

A method for the determination of triphenyltin and diphenyltin was developed by reversed-phase high-performance liquid chromatography with UV detection. Triphenyltin and diphenyltin were separated using a reversed-phase Symmetry C₁₈ column (150 × 3.9 mm, 5 m) with tetrahydrofuran-water-acetonitrile-glacial acetic acid (13:25:5:7, v/v) containing 0.05% triethylamine and 1.0% sodium acetate as mobile phase at 0.50 mL min^–1 and detection at 257 nm. The calibration curves were linear from 0.26 mol L^–1 to 1100 mol L^–1 for triphenyltin with a correlation coefficient of 0.9999 (n=12) and from 0.60 mol L^–1 to 1200 mol L^–1 for diphenyltin with a correlation coefficient of 0.9991 (n=12), respectively. The detection limits of triphenyltin and diphenyltin were 0.2 mol L^–1 and 0.4 mol L^–1, respectively. The method was successfully applied to the determination of triphenyltin and its metabolite diphenyltin in culture medium. The recoveries of triphenyltin and diphenyltin were in the ranges of 97.7% to 103.3% and 85.5% to 91.6%, respectively.     

Photometrische Bestimmung von Sulfid mit Jodnitrotetrazoliumchlorid

Zusammenfassung S^2– kann mit Jodnitrotetrazoliumchlorid (INT) innerhalb von 30 min photometrisch bestimmt werden. PO₄ ^3–, Cl^– und SO₄ ^2– in Konzentrationen bis zu 5 · 10^–2 mol/l, S₂O₃ ^2– bis zu 10^–4 mol/l und S₃O₆ ^2– bis zu 2 · 10^– mol/l stören nicht. Die untere Bestimmungsgrenze beträgt 3,4 · 10^–5 mol/l, entsprechend 1 g S^2–. Als relative Standardabweichung ergibt sich bei der Bestimmung von 3,2 g S²}±6,4 Rel.%.Die Untersuchungen wurden mit Hilfe eines Stipendiums der Alexander von Humboldt-Stiftung durchgeführt, der an dieser Stelle herzlich gedankt sei.     

Low-Temperature Adsorption–Luminescence Determination of Gold Using Silica Gel Chemically Modified with Mercapto Groups

Silica gel with mercaptopropyl groups covalently bonded to the surface extracts gold(III) from its hydrochloric solutions in a wide acidity range (from 6 M HCl to pH 8). An adsorption equilibrium is attained in no more than 5 min. The distribution ratio is 1.65 × 10⁴–1 × 10⁵ cm³/g. The intense yellow–orange luminescence (_max = 575 nm) appearing in the adsorbent phase under UV irradiation of wet liquid-nitrogen cooled adsorbates (77 K) is used for the low-temperature adsorption–luminescence determination of gold. The calibration plot is linear in the range of 1–100 g of gold per 0.1 g of adsorbent. The detection limit is 0.05 g/0.1 g of adsorbent. The relative standard deviation for the determination of more than 10 g of gold is no more than 5%.     

Determination of medecamycin by adsorptive stripping voltammetry with an activated electrode

The adsorptive and electrochemical behaviors of medecamycin were investigated on a glassy carbon electrode (GCE) pretreated by anodic oxidation at +1.8 V for 5 min in 0.025 mol l^–1 NH₃-NH₄Cl (pH 8.6) solution. An adsorptive stripping voltammetric method for the determination of medecamycin at the pretreated glassy carbon electrode has been developed. Medecamycin was accumulated in NH₃-NH₄Cl buffer (pH 9.0) at a potential of –0.7 V (vs. saturated calomel electrode (SCE)) for a certain time, and then determined by second-order differential anodic stripping voltammetry. The second-order differential anodic stripping peak current at +0.72 V was proportional to the concentration of medecamycin in the range 2.0 g ml^–1 to 50.0 g ml^–1. The detection limit (three times the signal-to-noise) was 1.0 g ml^–1 and the relative standard deviation of the results was 3.28% for eight successive determinations of 10.0 g ml^–1 medecamycin. This method has been applied to the direct determination of medecamycin in commercial tablets and spiked urine samples with satisfactory results.     

Flow-injection extraction-spectrophotometric determination of permanganate with the triphenylsulphonium cation

Summary Permanganate can be determined spectrophotometrically at 548 nm after flow-injection extraction into chloroform of the ion-associate triphenylsulphonium permanganate. The carrier stream was a pH 6 buffer containing 10% (w/v) ammonium fluoride and the reagent stream was 0.10% (w/v) triphenylsulphonium chloride. The injection rate was 20 h^–1. The calibration graph is linear up to 40 g ml^–1 and the detection limit is 1.10 g ml^–1 Mn(VII), based on injection volumes of 250 l. The system has been applied to the determination of manganese in steels and a cupro-nickel alloy.     

Polarographisches Verhalten der C2-Halogenkohlenwasserstoffe

Summary Investigations on the polarographic and voltammetric behaviour of organic halogen compounds were carried out in order to obtain information on the redox properties and how to develop determination and detection methods. In this second report the dp-polarographic behaviour of the halogen substituted C₂-compounds has been studied in different supporting electrolytes and in various solvents. The electrode processes are discussed and the possibilities for the polarographic determination of the C₂-halogen hydrocarbons. The detection limit is 0.25 g · ml^–1 and the linear current-concentration relationship is observed up to 25 g · ml^–1. A simple and rapid method is proposed for the dp-polarographic determination of 1,2-dibromoethane in gasoline; the relative standard deviation for 20 g · ml^–1 is ±1.8%.     

Photometric detection of cyclodextrins in liquid chromatography by using iodine generated electrochemically in-situ

A method has been developed for photometric detection of cyclodextrins (CD) in liquid chromatography using iodine (I₂) generated electrochemically in-situ. Iodide ion in the mobile phase was electrochemically oxidized to I₂ which was subsequently reacted with I^–, in an electrochemical flow cell, forming I₃^–. The absorbance of I₃^– was found to be greatly enhanced when CD were present in the mobile phase. The absorbance enhancement was caused by the change in the mole fraction of I₃^–, because of the inclusion reaction of I₃^– with CD. On the basis of this phenomenon, CD were detected by means of a photodiode-array UV–visible detector positioned downstream of the electrochemical flow cell. The signals were found to be linearly dependent on CD concentration. Because the formation constants of I₃^– with CD decrease in the order -CD>-CD>-CD, -CD was most detectable by the method. Detection limits were 1.0 mol L^–1 for -CD, 65 mol L^–1 for monoG1--CD, 100 mol L^–1 for -CD, and 200 mol L^–1 for -CD.     

Tris(2-ethylhexyl)phosphate as an extractant for quadrivalent tin,with subsequent determination with pyrocatechol violet in alloy samples

The solvent extraction of tin(IV) from chloride media withtris(2-ethylhexyl)phosphate is presented. Tin(IV) is extracted quantitatively from 2.75–3.20 mol dm^–3 hydrochloric acid using 6.38–6.91 mol dm^–3 tris(2-ethyl-hexyl)phosphate dissolved in toluene as an extractant. After back-extraction of tin(IV) with water from thetris(2-ethylhexyl)phosphate phase, it is estimated spectrophotometrically following complexation with pyrocatechol violet. The recommended range for determination of tin(IV) is 10–100 g. The probable extracted species is SnCl₄·2TEHP. The method is applicable to the analysis of alloy samples with a detection limit of 0.4 g/ml (for 10 g of tin) and a relative standard deviation between 0.21–0.32%.     

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.     

Simultaneous capillary GC-MS determination of triazines and amides in water

Summary A simultaneous capillary Gas Chromatographic-Mass Spectrometric (GC-MS) method is described for the determination of thirteen pesticides belonging to the triazine and amide families in water. The sample is extracted in liquid-liquid mode (dichloromethane) and then the determination of the residues is carried out by capillary gas chromatography with mass spectrometric detection in the Selected-Ion Monitoring mode (SIM). The average recoveries of spiked compounds are in the 78.4–135.4% range between the relative low level (0.100 g L^–1) and the relative high level (10.0 g L^–1). The limits of detection (LOD) are in the 0.009–0.128 g L^–1 range.     

Syntheses and Structures of Heterometallic Fe–Ta Chalcogenido Clusters

Two Fe–Ta containing sulfido complexes were prepared by the reaction of the metal halide salts with bis-trimethylsilylsulfide in the presence of PMe₃. The complexes demonstrate that coordination chemistry with iron sulfides can give access to a range of heterometallic complexes. In [Cl(Me₃P)Ta( ₂-S)₂( ₃-S)Fe(PMe₃)₂]₂ the two [Cl(Me₃P)Ta] units are arranged around one central Fe₂( ₂-S)₂ unit. In [(Me₃P)₄(MeCN)₂Fe^II]²⁺[(Me₃P)₂Ta^IVFe^II ₃( ₃-S)₄Br₄]^2– a [TaFe₃S₄]²⁺ cuboidal arrangement was observed. The complex salt forms a polymeric structure in the solid-state with weak H-bonds between the ions. The [(Me₃P)₂Ta^IVFe^II ₃( ₃-S)₄Br₄]^2– ion was characterised by magnetic measurements showing strong antiferromagnetic interactions between the metal centres.     

Gas enthalpimetry

Summary Gaseous sulphur dioxide has been used as a titrant for the determination of micro-amounts of the oxidants I₂, IO ₃ ^– , IO ₄ ^– and BrO ₃ ^– . The gas is injected into the solution, the heat change recorded and the step height measured. Ease of manipulation and simplicity of apparatus is an advantage of the method. Satisfactory results are obtained over the range 1–100 mol of oxidants. Standard deviations have been determined at the 15–60 gmmol level to be 0.2–1.3%.

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Gas-EnthalpimetrieI. Enthalpimetrische Bestimmung von Mikromengen einiger Oxidationsmittel unter Verwendung von Schwefeldioxid als gasförmigem Titrationsmittel

Zusammenfassung J₂, JO ₃ ^– , JO ₄ ^– und BrO ₃ ^– wurden mit gasförmigem SO₂ titriert. Das Gas wird in der Lösung injiziert, die Temperaturänderung registriert und die Stufenhöhe ausgewertet. Bequeme Handhabung und einfache Bauweise der Apparatur sind Vorteile des Verfahrens. Befriedigende Ergebnisse wurden von 1–100 Mol Oxidationsmittel erhalten. Im Bereich 15–60 Mol betrug die Standardabweichung 0,2–1,3%.

On leave from University of Chiengmai, Thailand.     

Determination of hexavalent chromium by using speciated isotope-dilution mass spectrometry after microwave speciated extraction of environmental and other solid materials

Precise and accurate determination of hexavalent chromium in different types of solid environmental sample is regarded as a technical challenge with significant potential error if historically accepted methods are used. Microwave-assisted alkaline extraction (0.5 mol L^–1 NaOH+0.28 mol L^–1 Na₂CO₃) followed by anion-exchange chromatographic separation and inductively coupled plasma mass spectrophotometric detection has been shown to provide accurate and precise results. To obtain a better understanding of potential species conversion during and/or after extraction steps, speciated isotope-dilution mass spectrometry (SIDMS) (EPA Method 6800) metrology has been successfully applied as a diagnostic tool with the modified accompanying extraction version of EPA Method 3060A. In our study, aggregate materials distributed over a large area of a major western US state were found to contain a high concentration of total chromium (195±13 to 709±19 g g^–1) and significant amounts of Cr⁶⁺ (141±6 to 341±29 g g^–1) which are at least three orders of magnitude higher than the US EPA threshold limit (0.5 g g^–1). Sediment samples from a major western US state, studied independently, were found to contain less (1.77±0.34 g g^–1) or no Cr⁶⁺ in the presence of significant total chromium.     

Catalytic Spectrophotometric Determination of Bromide Based on the Diphenylcarbazide–Chromium(VI)–Iodate Reaction

A new catalytic spectrophotometric method for the determination of bromide is proposed. Diphenylcarbazide reacts with chromium(VI) ions in an acid medium to give a violet complex. The method is based on the bromide-catalyzed oxidation of this violet complex by iodate followed by measuring the color change at = 542 nm spectrophotometrically. The reaction starts after an induction period. Bromide ions catalyze this reaction, so that the induction period is decreased by the addition of Br^–. The derivative of the absorbance with respect to time was calculated. The maximum absorbance difference (A _m) and thetime taken to reach the maximum difference (t _m) were measured from the derivative curve. These values are used as the measured parameters for bromide determination. Under optimum conditions bromide can be determined in the range of 0.5–8 g/mL. The detection limit is 0.25 g/mL, and the relative standard deviation for ten replicate measurements of 1 g/mL of bromide is 1.57%. The method was applied to the determination of bromide in the Persian Gulf water.     

Alternative spectrophotometric determination of niobium and tantalum with o-hydroxyhydroquinonephthalein in cationic surfactant micellar media

Summary The alternative and simultaneous spectrophotometric determination of niobium and tantalum was examined by using the colour development between o-hydroxyhydroquinonephthalein (Qnph) and niobium or tantalum in the presence of hexadecyltrimethylammonium chloride (HTAC) in strong acidic media. Beer's law was obeyed up to 10.0 g of niobium and up to 18.0 g of tantalum in a final volume of 10.0 ml. The apparent molar absorption coefficients for niobium and tantalum were 2.18×10⁵ and 2.09×10⁵ l mol^–1 cm^–1 with Sandell's sensitivities of 0.00042 g/cm² niobium at 520 nm and 0.00085 g/cm² tantalum at 510 nm, respectively. The alternative assay of niobium and tantalum was possible by using two methods: Method A — masking method with oxalic acid, Method B — acid adjusting-method using 50% sulfuric acid. These methods were 2–6-times more sensitive than other methods.Application of xanthene derivatives in analytical chemistry. Part XC. Part LXXXIX see ref [1]     

Simultaneous determination of neodymium and erbium in rare earth mixture with 5,7-dibromo-8-hydroxyquinoline and TX-100 by third-derivative spectrophotometry

The absorption spectra of 4f electron transitions of the complexes of neodymium and erbium with 5,7-dibromo-8-hydroxyquinoline in the presence of octylphenol poly(ethyleneglycol)ether have been studied by normal and third-derivative spectrophotometry. The proposed method is free of interference of other rare earths. The calibration graphs were linear up to 18 g/ml of neodymium and 21 g/ml of erbium (in the final solution). The derivative molar absorptivities are 395 l.mol^–1.cm^–1 for neodymium and 3421.mol^–1.cm^–1 for erbium. The corresponding values of Sandell's sensitivity were 0.36 and 0.49 g.cm^–1, respectively. The relative standard deviations evaluated from ten independent determinations of 2.5 g/ml of neodymium and erbium are 1.5 and 3.8% for neodymium and 1.8 and 4.1% for erbium in absence and presence of 70 g of lanthanum, respectively. The detection limits (signal to noise ratio=2) are 0.23 g/ml for neodymium and 0.30 g/ml for erbium. The method has been used for the determination of neodymium and erbium in mixed rare earths with satisfactory results.     

Chromotropic acid,a fluorogenic chelating agent for aluminium(III)

Complexation of aluminium(III) with the fluorogenic ligand chromotropic acid (4,5-dihydroxynaphthalene-2,7-disulfonic acid) has been revisited with the aim of using enhancement of the fluorescence intensity as an analytical tool. Complexation at the optimum pH4 was shown to lead to a 1:1 complex with a stability constant log ₁₁₀=18.4±0.7. The fluorogenic effect was thoroughly investigated. Nearly selective excitation of the chelate rather than the ligand could be achieved at wavelengths longer than 360 nm. For analytical purposes the main interfering ion was Ga³⁺. The strongest competing ligand was shown to be citric acid. Competitive complexation by acetate or formate ions can also make their use in a buffer at the usual concentration, 0.2 mol L^–1, questionable, whereas a 10^–2 mol L^–1 formic acid buffer was shown to be a good alternative. The calibration plot showed that the dependence of response on Al(III) concentration was linear up to 500 g L^–1; the detection limit was 0.65 g L^–1 (3SD _blank, n=10, SD=±1.4% at 10 g L^–1 and ±0.8% at 100 g L^–1). The analytical procedure was successfully applied to several samples of tap water and the results were in good agreement with those from AAS determination.