Fredric J. Feldman

The determination of chromium in biological materials by atomic absorption spectroscopy.

Abstract Biological samples were mineralized with a mixture of nitric, sulfuric, and perchloric acids. The chromium was oxidized to chromium(VI) followed by extraction into methyl isobutyl ketone in the cold. The ketone extract was aspirated into a fuel-rich hydrogen-air flame, and the absorption recorded using the 357.9 nm line of chromium. The limit of detection for chromium was found to be 10 p.p.b. Tissue chromium levels of normal albino rats were determined. Increased chromium values were observed for animals maintained on a high chromium diet compared to those fed a deficient diet.

Plasma Chromium after Glucose Administration

Sharp increases in the concentration of chromium in plasma were found in five subjects with normal glucose utilization after administration of glucose by mouth. This rise was not observed in two diabetics when glucose tolerance was impaired; however, it appeared when glucose tolerance was improved and when trace amounts of trivalent chromium were given as a dietary supple-ment. The source of chromium which became elevated was most likely an internal pool. Possibly there is a relation between chromium and insulin function.

Determination of nonmetals by atomic absorption spectrophotometry

Abstract Inorganic anions and organic compounds are determined using conventional atomic absorption apparatus. Several methods are studied in which the desired compound either limits or interferes with the determination or absorption of a metal. A direct relationship is obtained between the absorption by the metal and the amount of substance sought. Substances determined include orthophosphate, sulfate, iodide, sulfide, iodate, glucose, protein, 8-hydroxyquinoline, ethylenediaminetetraacetic acid, and ammonium pyrrolidine dithiocarbamate.

The atomic absorption spectroscopy of chromium

Abstract Conditions were studied for the determination of trace amounts of chromium by atomic absorption spectroscopy. Solution matrix, flame composition, and extraction procedures were the variables studied. A detection limit of 0.006 p.p.m. of chromium was observed with an air-hydrogen flame and methyl isobutyl ketone as the solvent.

Coulometric titration of blood ammonia

Abstract Blood ammonia after being separated by microdiffusion was determined by coulometric titration with electrogenerated hypobromite using a sensitive amperometric end point. An optimum pH of 8.6 for the titration was found to give reproducible results at all levels encountered. Time for a single analysis was 10–15 min.

Coulometric generation of molybdenum(v)

Abstract Molybdenum (V) was generated at a platinum cathode from 0.7 M molybdenum(VI) in 4 M sulfuric acid. A current efficiency of 99.9% was attained. A limiting current density of 0.05 mA/cm 2 /m M was found. The formal potential of the Mo(VI)–Mo(V) couple in 4 M sulfuric acid was determined to be ca. 0.55 V vs. N.H.E. Chromium(VI) solutions were titrated over a wide range of sample size and generating current. Amperometric titration curves were interpreted from current-voltage curves. Titrations could be performed in the presence of oxygen at the 1μeq. level. The effect of nitrate, perchlorate, orthophosphate, and chloride ions on the titration was determined.

Coulometric titration of oxidizing agents with electrogenerated molybdenum(V)

Abstract The coulometric titration of several oxidizing agents with Mo(V) has been investigated. Permanganate, persulfate, Ce(IV), vanadate, iodate, and ferricyanide reacted stoichiometrically. Bromine, bromate, iodine, and chlorate reacted too slowly to be titrated directly. Fe(III), tungstate, uranyl, and Ti(IV) did not titrate.

A semi-quantitative method for the determination of microgram amounts of manganese on millipore filters

Abstract A method is described in which the intensity of coloration of brown manganese dioxide on white Millipore filters is taken as the measure of the manganese content. A solution of manganese(II) is made strongly basic, whereupon manganese dioxide precipitates via its auto-oxidation. Optimum conditions for the precipitation are studied. Less than 0.5 μg of manganese can be determined.