J.R. Lindsay Smith

An E.S.R. Investigation of the Reactive Intermediate Generated in the Reaction Between FeII and H2O2 in Aqueous Solution. Direct Evidence for the Formation of the Hydroxyl Radical

The technique of E.S.R. spectroscopy, when employed in conjunction with a continuous flow system, provides direct evidence for the nature of free radicals formed from organic substrates in the presence of FeII and H2O2 in aqueous solution. It is shown, both via the identification of hydroxyl-radical adducts to alkenes and via the observed site-selectivity of radical attack, that the hydroxyl radical is formed as the reactive intermediate in the presence of various chelators (e.g. EDTA, DTPA). This approach also allows the rate constants for the FeII-H2O2 reaction in the presence of the different chelates to be determined; values obtained are in reasonable agreement with most of those measured by other methods. Examples of radical oxidation (by FeIII) and reduction (by FeII) are revealed.

Mechanisms of Mammalian Hydroxylation: Some Novel Metabolites of Chlorobenzene

1. The urinary metabolites of [14C]chlorobenzene administered orally to rabbits have been examined.2. The identified metabolites which account for 98-8% of the radioactivity in the urine include four previously unreported metabolites, namely, quinol, 3-chlorocatechol and o- and m-chlorophenylmercapturic acids.3. The distribution of isomeric mercapturic acids, free phenols and phenolic conjugates is reported.4. The major metabolites are r-chlorophenylmercapturic acid and the conjugates of 4-chlorocatechol.5. The metabolism of chlorobenzene is discussed in terms of an initial epoxidation to 3,4-chlorobenzene oxide.

Gas chromatographic analysis of aliphatic alcohols, diols and ethers using aromatic polymers

Abstract 1. The gas-solid separations of alcohols, diols and ethers on porous aromatic polymers are essentially the same as those using gas-liquid separation on Celite-Apiezon L columns, although the retention times on the latter are much shorter. 2. For liquids with similar boiling points the order of elution is diol, alcohol, ether, which reflects their increasing solubility in the polymer or in Apiezon L. 3. Within a class of compounds there is a linear relationship between long t r and boiling point of the eluent. Small divergencies from linearity arise from changes in the structure of the alkyl sidechain. 4. Modifying PAR-1 with polyethylene glycol has little effect on separation of alcohols and ethers, and the behaviour of the resulting column contrasts strongly with the Celite-PEG 1500 column. 5. Diols are separated on aromatic polymers ( e.g. PAR-1) without decomposition.

Gas chromatographic analysis of aliphatic amines : The use of ethylene glycols as stationary phases

Abstract The separation of amines on polyethylene glycol stationary phases is principally due to three types of solute—solvent attractive forces including donor and acceptor hydrogen-bonding. It is suggested that differences in retention time are principally due to differences in the entropy of formation of the acceptor hydrogen bond. The retention times of amines on a series of ethylene glycols are compared with each other and with those obtained using Apiezon L. Non-polar columns are most satisfactory for the separation of amines within a homologous series, but for amines with similar boiling points, as polar a column as possible should be used, although peak tailing becomes more apparent and may impair an efficient separation. For the most polar stationary phases, the support material must be coated with polyethyleneimine. If potassium hydroxide is used, the primary and secondary amines may not be eluted.

High-performance liquid chromatographic determination of low levels of primary and secondary amines in aqueous media via derivatisation with 1,2-naphthoquinone-4-sulphonate

Abstract 1,2-Naphthoquinone-4-sulphonate has been used as a derivatising agent for a variety of primary and secondary aliphatic amines in dilute aqueous solutions prior to separation by reversed-phase high-performance liquid chromatography. Although the method is generally reliable, it does not work with some amines and this was explained in terms of steric hindrance during derivatisation and failure to transfer derivatives of hydrophilic amines to the organic phas during the extraction/concentration stage.

Aflatoxin B1 activation to a plasmid mutagen by a chemical model of cytochrome P-450

Aflatoxin B1 (AFB1) was oxidised by a chemical model of cytochrome P-450 and the products obtained analysed by reversed-phase hplc. The oxidation system employs a water-insoluble iron(III)porphyrin catalyst (tetraphenylporphinatoiron(III) chloride; FeTPPCl) and an oxygen donor, iodosylbenzene (PhIO). The two AFB1 products obtained from this reaction were derived by initial oxidation across the 8-9 double bond of AFB1 and subsequent breakdown of AFB1-8,9-epoxide, the compound postulated to be the ultimate carcinogenic and mutagenic derivative of AFB1. Oxidation of AFB1 by the porphyrin-catalysed system in the presence of calf-thymus DNA, resulted in the formation of AFB1-DNA adducts identical to those formed in vivo and in vitro after liver mono-oxygenase activation. The chemical model system was therefore used on a microscale to react AFB1 with plasmid pHR1800, a plasmid containing the genes for beta-lactamase (amp-r) and galactokinase (galK). AFB1-modified plasmid DNA was then transformed into E. coli AB1886 (uvrA-) and the effects of the AFB1-DNA adducts on plasmid survival and the ability of pHR1800-transformed bacteria to metabolise galactose, were then studied. The results showed an AFB1 dose-dependent decrease in plasmid survival and increase in the mutation frequency of the galK gene only when the complete oxidation system was used to generate the reactive AFB1 metabolite.

A simple chromatographic procedure for the concurrent estimation of urinary 4-hydroxy-3-methoxymandelic acid (HMMA) and homovanillic acid (HVA) using a scanning technique

A rapid and simple procedure is described for the concurrent determination of 4-hydroxy-3-methoxymandelic acid (HMMA) and homovanillic acid (HVA). The acids are separated by chromatography and estimated by a scanning technique. The urinary output of HMMA and HVA over 24 h from 123 normals (80 males, 43 females) gave mean values of 3.3 +/- 0.94 and 4.9 +/- 1.3 mg, respectively. There was no significant difference in the 24 hour urinary output of HMMA and HVA between the male and femal groups.

Gas chromatographic separation of aliphatic diamines

Abstract The separation of aliphatic diamines by gas—liquid chromatography using a polar and a non-polar stationary phase is described and the results are compared with those obtained using aromatic polymer beads treated with polyethylene imine. For a homologous series of diamines, Apiezon L on alkaline-washed Celite is found to be the most satisfactory material, while for diamines with similar boiling points, the polar phase Carbowax 20M is most efficient. The different behaviour of the column materials is discussed in terms of hydrogen-bonding and other intermolecular forces between the amine and the liquid phase.

The degradation of lubricants in gasoline engines: Development of a test procedure to evaluate engine oil degradation and its consequences for rheology

Tests have been undertaken to study the effects of engine parameters and lubricant blends on oil degradation and engine components. A single cylinder spark ignition research engine was used for this work. The cam shaft was run on fully formulated oil and the crank and piston ring pack on the test oils. Samples were extracted from the sump, whilst the engine was running under controlled conditions, and rheological and chemical analysis data obtained from these samples. The methodology behind the testing and the engine set up is presented, as are results for the viscosity, sump carbonyl concentration and the end of test component condition for the four tests undertaken. Comparisons between the oil blends, engine parameters and results are discussed before conclusions are drawn and areas for further work highlighted.

Lubricant Degradation Studies Using a Single Cylinder Research Engine

With increasing pressure on engine oil manufacturers to extend oil drain intervals and reduce fuel consumption, whilst changing the composition of fully formulated oils to meet new CEC, ILSAC and OEM specifications, there is ever increasing need to understand the effect of oil degradation on the operating conditions and tribological performance of engines. This poster presents mechanical changes made to a single cylinder research engine to enable the study of lubricant degradation, its transport and how this links to piston assembly tribology. A summary of the research undertaken using these changes and a sample of results obtained to date are also presented.Copyright