Light-induced decay of free radicals in wool keratin

The kinetics of free radicals created by blue light in wool keratin are interpreted in terms of two decay processes: a first-order decay occurring spontaneously even in the dark, and another first-order decay directly proportional to the light intensity. This interpretation is supported by an analysis of previous experimental results and by more direct new experimental evidence.     

Comparison of osmotic pressures from EMF measurements,obtained according to cell-model considerations and exact Gibbs-Duhem integrations

Osmotic pressures of aqueous solutions of poly(diethylaminoethyl methacrylate) hydrochloride, in equilibrium with a precipitate of the un-ionized polybase, at various concentrations of polymer and NaCl in solution and at different values of pH are derived from emf measurements and the “cell” theory for polyelectrolytes. Single-ion activities are evaluated according to two procedures. The first is based on measurements with ion-specific electrodes versus a calomel electrode. The second makes use of a salt bridge, but assumes that the co-ions have activity coefficients equal to the mean activity coefficient of the salt in a polyelectrolyte-free solution of the same concentration. The results show that the calculated values of the osmotic pressures are consistent with those obtained by the exact integration of the Gibbs-Duhem relationship, when the first procedure is employed. If, however, the single-ion activities are evaluated by the second procedure, the osmotic pressures obtained are consistently lower by about 10%. These differences arise because the two methods yield different values of the activity coefficients of the single ions.     

Theoretical considerations on the estimation of sample matrix effects in analytical chemistry

Methods are suggested for evaluating the magnitude of matrix effects on the results of analysis.     

DETERMINATION OF INTRINSIC CONSTANTS FOR THE KINETICS OF GROWTH AND DECAY OF FREE RADICALS IN ILLUMINATED KERATIN

Abstract— The growth and the decay of free radicals in illuminated keratin of five samples of wool have been studied by electron paramagnetic resonance. Illumination of the different samples varied from 10^-9 to 10^-7 Einstein cm^-2s^-1. The paramagnetic resonance spectra were measured both during illumination and during the decay of signals in the dark. The curves obtained during illumination gave two typical shapes: one approaching the apparent "saturation value", and the other passing through a maximum and then decreasing despite continuing illumination. All the above results are discussed in terms of only two prevalent free-radical species, whose growth and decay are determined for each species by a single intrinsic growth constant, and a single intrinsic decay constant. These four constants allow a reasonable fit for the complete behaviour of all five samples.     

Gas-chromatographic quantitation of lindane in household insecticide spray cans

Summary A method was developed for the determination of the lindane content of commercial household insecticide spray aerosols. After the propellant is removed from the chilled contents of the spray packages the hydrocarbon solution is analysed for its lindane content by electron-capture gas chromatography. Pure -isomer of hexachlorocyclohexane serves as the internal standard. Experimental error is ± 5%.

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Gas-chromatographische Bestimmung von Lindan in Haushalts-Spraydosen

Zusammenfassung Das Treibmittel wird durch Ausfrieren abgetrennt und die Insecticidlösung gas-chromatographisch mit Electron-capture Detektor analysiert. Das reine -Isomere dient als innerer Standard. Der Fehler beträgt ± 5%.

     

Determination of osmotic coefficients in polyelectrolyte solutions by potentionmetric measurements during phase separation

A method of evaluating osmotic coefficients of polyelectrolyte solutions is suggested for systems in which a two-phase equilibrium is maintained between the polymer solution and a polymer precipitate so that the “polymer” terms C_pdμ_p in the Gibbs-Duhem relationship may be neglected. The method is applied to a polybase system, and the osmotic coefficients calculated from the experimental data are discussed in terms of the theory of Alexandrowicz. The results are found to be in line with the above theory but the characteristic parameter ?_p, the fraction of free counterions, is about twice as large as values previously observed in polyacids.     

Optimization of analytical methods based on non-linear asymptotic calibration graphs: Effect of the Time of Hydrolysis on the Enzymatic Determination of Pyridostigmine

A method for enzymatic determination of pyridostigmine is considered. The nonlinear calibration graphs obtained are functions of nine independent variables. The optimization of the curves is discussed, with the relative error as the criterion of optimization. A graphical method is suggested, which allows easy determination of the relative error, of the best concentration for sampling, and of the limit of response. A shortcut method of optimization for asymptotic calibration curves is suggested, and illustrated by optimizing the time of hydrolysis of acetylcholine by cholinesterase. Some determinations of pyridostigmine in water, urine and bovine serum are presented, employing the suggested method.     

Optimization of non-linear calibration graphs as applied to an enzymatic assay of pyridostigmine

The enzymatic method for the determination of pyridostigmine in body fluids was investigated in order to optimize the various parameters that affect the calibration graphs. Six variables were optimized, each with respect to three criteria of optimization. The optimum values were found to be different for aqueous and plasma calibration graphs, but the differences are only slight. The former, roughly calculated, values of the variables were found to be fairly satisfactory. The suggested graphical method for optimization was found to be very helpful.     

Further study of individual ion activities in pure aqueous sodium chloride solution

The e.m.f. values between a chloride electrode and a reference electrode were measured in aqueous NaCl solutions between 10(-5) and 6 m, saturated KC1 and 1M KNO(3) bridges being used. The effect of the various liquid junctions is calculated and discussed. The consistency of the results is inspected, assuming either the MacInnes or the Guggenheim convention. The choice of different reference points for the standardization of the e.m.f.'s and for the activity coefficients is discussed. A comparison is made between the results obtained with an Ag/AgCl electrode of the second kind and a solid membrane chloride electrode.