Adam Shatkay

EPR STUDY OF WOOL IRRADIATED WITH BLUE LIGHT

Abstract— Wool fibres were exposed to visible light in the blue range. The free radicals created by the illumination were studied using electron paramagnetic resonance. It is shown that by control of the light intensity and frequency it is possible to get considerable insight into the mechanism of the creation and the decay of the free radicals. The radical population under the above conditions appears to consist of an initial stable radical insensitive to radiation, and three other radicals, two of which follow decay kinetics considerably different from that of the remaining free radical. All the latter three radicals are probably caused by N–H or C–H bond scission.

DECAY KINETICS OF FREE RADICALS IN IRRADIATED PROTEINS

Abstract— A detailed analysis is presented of the decay kinetics of free radicals in irradiated biopolymers. Available data in the literature are critically evaluated and new data for irradiated keratin are presented. It is shown that a rigorous analysis of the data available in the literature leads to more detailed information on the decay mechanisms than the conclusions which have been previously given; in some cases the analysis leads to mechanisms contradicting those claimed in the literature.

Comparison of different methods of quantitative analysis employing gas-liquid chromatography, illustrated by the determination of water in organic solvents

Abstract The methods used in quantitative analysis employing gas-liquid chromatography are critically examined, and a division into three major categories is suggested. The various methods have been applied to the determination of water in organic solvents. It was found that for a moisture content of 0.1–5 wt.-% the external standard method is preferable to the internal standard method, and the method of standard additions is the least satisfactory. The “volume effect” and the “solute effect” were examined for various water-standard-solvent systems, and the errors were evaluated.

SIMULTANEOUS GROWTH AND DECAY OF FREE RADICALS IN IRRADIATED PROTEINS

Abstract— The electron paramagnetic resonance signals due to free radicals created in illuminated keratin have been studied during illumination and also during the decay of the signal in the dark. A number of mechanisms suggested to account for the simultaneous growth and decay of radicals during illumination is considered but only one of these is capable of accounting for the experimental results.

Discrepancies in curve fitting for direct and linearized functions, illustrated with transient electrode potentials

Abstract The discrepancies arising from curve-fitting with direct equations or with linearized equations are discussed. The argument is illustrated with three equations purporting to represent transient potentials in ion-selective electrodes. The advantages and the disadvantages of using direct equations instead of linearized ones are considered in detail. It is shown that the use of “pseudo-linearized” equations is inferior in all respects, and can yield significantly wrong results.

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.

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

Abstract 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.

Enzymatic determination of pyridostigmine in the presence of endogenous cholinesterase

Abstract An enzymatic method for the assay of pyridostigmine in body fluids is described, in which the degree of inhibition of the endogenous cholinesterase is utilized in constructing the calibration curve. Hydrogen-ion activity is measured potentiometrically (±0.1 mV). Samples are introduced directly, without any extraction, concentration or derivatization. The effect of the time of inhibition is discussed. Cholinesterase inhibition is calculated for various concentrations of pyridostigmine, and summarized graphically. The assay is applied to blood plasma from humans and animals and found to be reliable, within 20%, down to 10 −8 g mol −1 concentrations of pyridostigmine.

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

Abstract 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.

Gas-chromatographic quantitation of lindane in household insecticide spray cans

ZusammenfassungDas Treibmittel wird durch Ausfrieren abgetrennt und die Insecticidlösung gas-chromatographisch mit Electron-capture Detektor analysiert. Das reine α-Isomere dient als innerer Standard. Der Fehler beträgt ± 5%.SummaryA 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 α-isomer of hexachlorocyclohexane serves as the internal standard. Experimental error is ± 5%.