Determination of elements by atomic absorption spectrometry after destruction of blood in the oxygen flask

Summary A new method for mineralisation of blood is proposed. A known volume of blood is combusted in an oxygen-filled flask which contains 11 nitric acid as absorbent for the combustion products. The elements are determined by flame photometry and atomic absorption. The results are compared with results from wet digestion and dilution procedures.

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Bestimmung von Elementen im Blut durch AAS nach Veraschung im Sauerstoffkolben

Zusammenfassung Ein neues Verfahren der Mineralisierung von Blut wurde vorgeschlagen. Ein gemessenes Volumen Blut wird im sauerstoffgefüllten Kolben in Gegenwart von Salpetersäure (11) verascht. Die Elemente werden durch Flammenphotometrie bzw. Atomabsorption bestimmt. Die Ergebnisse wurden mit jenen nach nasser Veraschung und Verdünnung verglichen.

     

Determination of ethambutol in pharmaceutical preparations by atomic absorption spectrometry,spectrophotometry and potentiometry

Simple methods are described for the determination of ethambutol in pharmaceutical preparations. They are based on the reaction of the drug with copper phosphate suspension in a borate buffer of pH 9.2, whereby a blue 11 water-soluble copper-ethambutol complex is quantitatively formed. Four portions of the reaction solution are used for (i) measurement of copper by atomic-absorption spectrometry at 324.7 nm; (ii) potentiometric titration with EDTA with use of a solid-state copper ion-selective electrode; (iii) visual titration with EDTA (copper-PAN indicator); and (iv) spectrophotometric measurement of the copper-ethambutol complex at 640 nm. The results obtained are in good agreement and are better than those of the British Pharmacopoeia (BP) method.     

New colorimetric methods for the determination of trazodone HCl,famotidine, and diltiazem HCl in their pharmaceutical dosage forms

Two sensitive and simple spectrophotometric methods are developed for the determination of trazodone HCl, famotidine, and diltiazem HCl in pure and pharmaceutical preparations. The methods are based on the oxidation of the cited drugs with iron(III) in acidic medium. The liberated iron(II) reacts with 1,10-phenanthroline (method A) and the ferroin complex is colorimetrically measured at 510 nm against reagent blank. Method B is based on the reaction of the liberated Fe(II) with 2,2-bipyridyl to form a stable colored complex with lambda(max )at 520 nm. Optimization of the experimental conditions was described. Beer's law was obeyed in the concentration range of 1-5, 2-12, and 12-32 microg mL(-1) for trazodone, famotidine, and diltiazem with method A, and 1-10 and 8-16 microg mL(-1) for trazodone and famotidine with method B. The apparent molar absorptivity for method A is 1.06x10(5), 2.9x10(4), 1.2x10(4) and for method B is 9.4x10(4 )and 1.6x10(4), respectively. The suggested procedures could be used for the determination of trazodone, famotidine, and diltiazem, both in pure and dosage forms without interference from common excipients.     

Construction and Evaluation of a Promazinium Cation-Selective Electrode

 The construction of a plasticised PVC matrix-type promazinium cation-selective membrane electrode and its use in the potentiometric determination of promazine hydrochloride in pharmaceutical preparations are described. It is based on the use of the ion-associate species, formed by promazinium cation and tetraphenylborate (TPB) counter ion. The basic electrode performance characteristics are evaluated according to IUPAC recommendations. It exhibited a linear response for 1 × 10⁻²−1 × 10⁻⁵ M of promazine hydrochloride solutions with a cationic Nernstian slope over the pH range 2–6. Common organic and inorganic cations showed negligible interference. Direct potentiometric determination of 1 × 10⁻²−1 × 10⁻⁵ M aqueous promazine hydrochloride using this membrane electrode system showed an average recovery of 99.5% with a mean standard deviation of 1.5%. This electrode was successfully used for monitoring the titration of promazine hydrochloride with sodium tetraphenyl borate and for determining promazine hydrochloride in ampoules. Received June 15, 2001 Revision November 6, 2001     

Polarographic analysis. II

Summary The polarography of hexavalent uranium in sulphuric acid solutions of different concentrations and solutions containing sodium sulphate is studied. In 0.01 M H₂SO₄ three waves are obtained corresponding to the successive reduction of U^VI to U^V, U^V to U^IV and U^IV to U^III. The second and third waves intermingle by increasing the H₂SO₄ concentration up to 0.055 M or by adding Na₂SO₄ or sulphosalicylic acid. In 0.25 M H₂SO₄ or in the presence of EDTA the second wave shifts to less negative potentials and intermingles with the first wave, forming a single wave along which reduction of U^VI gives a mixture of U^V and U^IV. The diffusion current of this wave increases up to 1 M H₂SO₄ and then decreases above this acidity. The diffusion current measured at –0.6 V is proportional to the U^VI concentration in the presence of 0.25–0.6 M H₂SO₄. This is not the case in the presence of EDTA. The proportionality is better at lower than at higher acidity.Part I: See Z. analyt. Chem.174, 4 (1960).     

Triangulating point sets in space

A setP ofn points inR ^d is called simplicial if it has dimensiond and contains exactlyd + 1 extreme points. We show that whenP containsn interior points, there is always one point, called a splitter, that partitionsP intod + 1 simplices, none of which contain more thandn/(d + 1) points. A splitter can be found inO(d ⁴ +nd ²) time. Using this result, we give anO(nd ⁴ log_1+1/d n) algorithm for triangulating simplicial point sets that are in general position. InR ³ we give anO(n logn +k) algorithm for triangulating arbitrary point sets, wherek is the number of simplices produced. We exhibit sets of 2n + 1 points inR ³ for which the number of simplices produced may vary between (n – 1)² + 1 and 2n – 2. We also exhibit point sets for which every triangulation contains a quadratic number of simplices.Research supported by the Natural Science and Engineering Research Council grant A3013 and the F.C.A.R. grant EQ1678.     

Highly stable organic monolayers for reacting silicon with further functionalities: the effect of the C-C bond nearest the silicon surface

Crystalline Si(111) surfaces have been alkylated in a two-step chlorination/alkylation process using various organic molecules having similar backbones but differing in their C-C bond closest to the silicon surface (i.e., C-C vs C=C vs C[triple bond]C bonds). X-ray photoelectron spectroscopic (XPS) data show that functionalization of silicon surfaces with propenyl magnesium bromide (CH3-CH=CH-MgBr) organic molecules gives nearly full coverage of the silicon atop sites, as on methyl- and propynyl-terminated silicon surfaces. Propenyl-terminated silicon surface shows less surface oxidation and is more robust against solvent attacks when compared to methyl- and propynyl-terminated silicon surfaces. We also show a secondary functionalization process of propenyl-terminated silicon surface with 4'-[3-Trifluoromethyl-3H-diazirin-3-yl]-benzoic acid N-hydroxysuccinimide ester [TDBA-OSu] cross-linker. The Si-CH=CH-CH3 surfaces thus offer a means of attaching a variety of chemical moieties to a silicon surface through a short linking group, enabling applications in molecular electronics, energy conversion, catalysis, and sensing.     

Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

Technetium-99 is a prevalent fission product from nuclear waste. The long half-life (211,000 yr) and environmental mobility of pertechnetate (TcO₄⁻) render Tc particularly challenging to isolate and stabilize. Here we present two approaches for development of potential wasteforms using titanium dioxide, TiO₂. Approach 1 is a low temperature chemical synthesis of TiO₂ doped with Tc(IV) from TcO₄⁻ intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge-shared Tc(IV) pairs. Approach 2 utilizes TiO₂ to photocatalytically reduce TcO₄⁻ to Tc(IV) stabilized on the surface of or within the TiO₂ lattice. The %Tc removed from solution and adsorbed to TiO₂ is pH dependent, with the maximum Tc(IV) adsorbed at pH 3–4 as either TcO₂ or edge-sharing Tc(IV) octahedra. The Tc(IV)-TiO₂ composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing).