Showing papers in "Analytical Chemistry in 1962"

Chromatographic Separation of Peptides on Ion Exchange Resins. Separation of Peptides from Enzymatic Hydrolyzates of the α,β, and γ Chains of Human Hemoglobins.

Abstract: Isolation of components in a mixture is most effectively accomplished by great alteration of conditions from step to step in the separation. This principle has been applied to the separation of complex mixtures of peptides in protein hydrolyzates. Excellent results have been obtained by chromatographing first on the cation exchanger Dowex-50 and then rechromatographing on the anion exchanger Dowex-1. Volatile developers were employed throughout. Experimental procedures are presented, and results are given of their application to the separation of peptides from human hemoglobins A and F.

Gas Chromatographic Analysis of Head Space Gas of Dilute Aqueous Solutions.

Abstract: Enrichment of head space gas in sulfides, carbonyls, esters, and alcohols prior to chromatographic analyses was accomplished by adding anhydrous sodium sulfate salt to dilute aqueous solutions. It was possible to analyze head space gas from aqueous solutions below the 1 p.p.m. level. In addition to retention times, evidence for identification of these trace organic compounds was obtained by eliminating peaks with selective qualitative reagents. Evidence for the identification of the 18 components of a complex mixture of sulfides, carbonyls, esters, and alcohols at the 1 p.p.m. carbonyls was made to establish the limits of sensitivity of the method.

Activation Analysis for Oxygen and Other Elements by Helium-3-Induced Nuclear Reactions.

Abstract: A rapid activation analysis was performed for oxygen in beryllium, thorium, and Mylar samples. The ultimate sensitivity is in fractions of a part per billion. Milligram amounts of total sample are sufficient. The method can be used to analyze for other elements and for specific nuclides. More than one element can be determined in the same activation. The sample need not be destroyed. Because of the low binding energy of the He3 incident projectile, many He/sup 3/ nuclear reactions are exoergic, permitting radioactive products to be formed with large cross section from a beam of low kinetic energy. The absolute excitation function was determined for the production of F/sup 18/ from O/sup 16/ reaction with He/sup 3/ ions of kinetic energy up to 31 Mev. The induced radioactivity was measured by calibrated endwindow proportional counters and NaI scintillation spectroscopy. Brief bombardment of a 0.001-inch thorium foil with 0.01 mu a of He/sup 3/ gave sufficient F/sup 18/ radioactivity from O/ sup 16/ impurity to distinguish easily the 0.51-Mev annihilation radiation from the nuclear gamma rays emitted thorium and its daughters. Methods for eliminating or minimizing interferences more » are discussed. Nuclear reactions of lowenergy He/sup 3/ ions with nuclides up to Ca/sup 48/, product half lives, and reaction Q values are listed. (auth) « less

Anion Exchange Resin Separation of the Rare Earths, Yttrium, and Scandium in Nitric Acid-Methanol Mixtures.

Abstract: The adsorption of the rare earths, yttrium, and scandium from nitric acid--methanol solutions was studied using strongly basic anion exchange resins. Adsorption measurements were made at room temperature using the column elution technique and employing emission spectrographic analysis. Distribution coefficients were a function of both the volume percentage of alcohol and of the nitric acid concentration. The rare earths were eluted from a column in order of decreasing atomic number with little individual than terbium had relatively large separation factors. Yttrium behaved like lutetium, while scandium was not adsorbed to an appreciable extent. Application of the system for macro separations was demonstrated in the preparation of extremely pure rare earths and for fractionation of crude rare earth mixtures. Finally, the simplicity of operation is attractive for analytical separation of trace impurities.