Indirect determination of cyanide by molecular emission cavity analysis

Nanogram amounts of cyanide were indirectly determined by molecular emission cavity analysis. The method is based on the reaction of cyanide with sulphite-formaldehyde addition compound and the measurement of the S₂ emission produced either from the sulphite released or from the addition compound. The relative standard deviations are 2.13% and 1.66% and the recoveries are 99% and 100% using the released sulphite peak and the addition compound peak, respectively. Potential interfering anions were investigated.     

Generalized Dirichlet to Neumann operator on invariant differential forms and equivariant cohomology

In recent work, Belishev and Sharafutdinov show that the generalized Dirichlet to Neumann (DN) operator Λ on a compact Riemannian manifold M with boundary ∂M determines de Rham cohomology groups of M. In this paper, we suppose G is a torus acting by isometries on M. Given X in the Lie algebra of G and the corresponding vector field XM on M, Witten defines an inhomogeneous coboundary operator dXM=d+ιXM on invariant forms on M. The main purpose is to adapt Belishev-Sharafutdinov?s boundary data to invariant forms in terms of the operator dXM in order to investigate to what extent the equivariant topology of a manifold is determined by the corresponding variant of the DN map. We define an operator ΛXM on invariant forms on the boundary which we call the XM-DN map and using this we recover the XM-cohomology groups from the generalized boundary data (∂M,ΛXM). This shows that for a Zariski-open subset of the Lie algebra, ΛXM determines the free part of the relative and absolute equivariant cohomology groups of M. In addition, we partially determine the ring structure of XM-cohomology groups from ΛXM. These results explain to what extent the equivariant topology of the manifold in question is determined by ΛXM.     

Adducts of coordination compounds—12: New hydrogen dinitrates and their structures

The new compounds trans-[Ru(pyr)₄Cl₂[H(ONO₂)₂] and [C₁₃H₉NH][H(ONO₂)₂] have been characterised (where pyr is pyridi     

Molecular emission cavity analysis: Part 24. Determination of germanium,gallium and thallium

Germanium (10–500 ng) is determined by measuring its GeCl emission at 455 nm in a carbon cavity in a hydrogen—nitrogen—air flame. Similarly, gallium gives a violet GaI emission and a bluish white GaBr emission with maximum intensities at 391 and 350 nm. respectively. These emissions can be used for the determination of nanogram amounts of gallium or bromide, and microgram amounts of iodide. Thallium (20–2000 ng) is determined by measuring its atomic emission produced in an oxy-cavity at 377.5 nm. The effects of interferences on germanium, gallium and thallium emissions are described.     

Consecutive indirect titration of periodate and iodate with EDTA

Periodate and iodate (μmol amounts) are determined successively in the same solution by their selective oxidation of iron(II) at pH 2.0 and in acetic acid, respectively. The resultant iron(III) is titrated with EDTA solution to a sulphosalicylic acid end-point. Bromate—iodate mixture can be titrated similarly.     

Molecular emission cavity analysis: Part 23. Determination of Nitrite and Nitrate after Conversion to Nitrogen Monoxide

Molecular emission cavity analysis is applied to the determination of nitrite and nitrate after their reduction to nitrogen monoxide by iodide or zinc. The white emission stimulated from nitrogen monoxide in an oxy-cavity placed in a hydrogen—nitrogen diffusion flame is measured at 526 nm. Calibration graphs are linear up to 300 μg N ml^-1; the detection limit is 0.5 μg N ml^-1 for nitrite and 2 μg N ml^-1 for nitrate. There are few interferences. Procedures for the determination of nitrite and nitrate in admixture are described.     

Effect of pH on lipid oxidation of red onion skin extracts treated with washed tilapia (Oreochromis niloticus) muscle model systems

The aim of the study was to investigate the effect of pH on the lipid oxidation of red onion skin extracts (ROSEs) treated with washed tilapia muscle model systems (WTMS). Minced and buffered washed samples were prepared at pH 6.3 and 6.8. The WTMS were treated with2 different concentrations of red onion skin prior to storage for 5 days. Lipid oxidation was investigated via peroxide values (PVs), thiobarbituric acid reactive substances (TBARS), and the formation of volatile compounds. Fatty acid profiles of the samples were also identified. The ROSEs were able to significantly suppress the PV (~71%) and TBARS (~42%) formation. Hexanal and octanal formations in the WTMS were relatively less in the ROSE-treated samples. The WTMS samples prepared at pH 6.3 were more vulnerable to lipid oxidation than those prepared at pH 6.8. Red onion skin polyphenols may increase the lag phase of lipid oxidation, depending on pH levels, resulting in the shelf life extension of raw fish.     

Indirect determination of amino acids by molecular emission cavity analysis

An indirect method for the determination of ca. 10^?4 M amino acids is described which is based on the reaction of the latter with 2,4,6-trinitrobenzene-1-sulphonic acid at pH 11.7 and the measurement of the S₂ emission in a hydrogen-nitrogen flame that is produced from the resulting compound after the addition of hydrochloric acid. The optimum conditions for the determination of amino acids were investigated. The amino acids examined were glycine, alanine, valine, methionine, serine, threonine and histidine.