A high performance liquid chromatography (HPLC) procedure using a LiChrosorb-NH₂ column and a eluant buffer of 75:25 (v/v) of acetonitrile:0.05 M KH₂P0₄, pH 5.95, was developed for the successful separation and determination of ascorbic and erythorbic acids in selected food samples. Application of the method, which is sensitive, rapid and simple, for the analysis of ascorbic and erythorbic acids in frozen apples, potato products, fruit and vegetable concentrated juices, frozen juices, natural and artificial flavor drink mixes, and Hi-C drinks gave satisfactory results. Dehydroascorbic and dehydroerythorbic acids in these samples could also be determined after reduction with dithiothreitol. It was verified by HPLC that the presence of erythorbic acid affected the determination of ascorbic acid levels by the spectrophotometric method by causing elevated absorbance readings and hence, abnormally high values. Erythorbic acid seriously affects the true determination of ascorbic acid contents in food samples by the spectrophotometric method. The use of HPLC is recommended for the routine analysis of ascorbic acid of those samples containing both ascorbic and erythorbic acids. / Graduation date: 1986

The roles of vitamin C and the effects of supplementation have been under investigation for many years. The purpose of this study was to use high performance liquid chromatography to assess the presence of vitamin C in human sweat, to evaluate sweat as a possible excretory route for vitamin C and to note any effects of vitamin C supplementation. Vitamin C in sweat was determined in samples from 10 active men and women prior to supplementation and weekly for 4 consecutive weeks as the vitamin C supplements were with a reverse-phase liquid chromatograph (Model ALC-202) equipped with a solvent delivery system (Model 6000, Waters Association).The presence of vitamin C in sweat samples was indicated by comparing peaks to those seen with vitamin C observed in sweat samples. Vitamin C was observed in sweat at the end of the first week of supplementation. The pres C.However, 4 and 5 when standards. During the first week of the study, when subjects' diets were not supplemented, vitamin C was not observed in sweat samples. Vitamin C was observed in sweat at the end of the first week o supplementation. The presence of vitamin C in sweat diminished during weeks 4 and 5 when intakes were supplemented with 750 mg and 1000 mg, respectively. It appeared that supplementation affected the presence of vitamin C in human sweat until plasma or tissues were saturated, at which point absorption may have decreased and other means of excretion may have been enhanced.

Shiu Kwok Keung. / Bibliography: leaf 75 / Thesis (M.Ph.)--Chinese University of Hong Kong, 1984

Digitized by Kansas Correctional Industries

An equals sign appears under the "L" in the title. / Digitized by Kansas Correctional Industries

Thesis (Ph. D.)--Ohio State University, 1970. / Includes vita. Includes bibliographical references (leaves 67-77). Available online via OhioLINK's ETD Center.

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The concentration of ascorbic acid in the plasma was determined on four levels of ascorbic acid intake for seven day periods in 1946-47 and on three levels of ascorbic acid intake for ten day periods in 1947-48. The subjects, eight girls and eight boys, were 16 to 19 year old freshman students at Oregon State College. All of the food eaten by the subjects during the experimental periods was weighed and the quantities were recorded. The reduced ascorbic acid in the foods was determined after each meal by the method of Loeffler and Ponting (1942) and daily fasting plasma ascorbic acid values were determined by the micro-method of Farmer and Abt (1936). The data in this study were analyzed statistically by testing the significance of the differences between the means and by analysis of variance. The recommended allowance of the National Research Council (1945) for these subjects (80 mg for the girls and 100 mg for the boys) did not maintain mean plasma values as high as their respective means during the saturation period when they were receiving 200 mg of crystalline ascorbic acid in addition to the ascorbic acid from their food. On the recommended allowance all the mean plasma values for the girls were above 0.80 mg per cent, ranging from 0.83 to 1.07. The boys values ranged from 0.67 to 0.91 mg per cent; two out of seven values were below 0.80 mg per cent (data for one boy were excluded due to illness). A decrease in ascorbic acid intake to 10 mg less than the recommended allowance of the National Research Council made a statistically significant decrease in the plasma ascorbic acid concentration for only two of the eight girls and for one of the seven boys. The plasma ascorbic acid concentrations of these subjects showed individual variation even when the ascorbic acid intake was considered on the basis of mg of ascorbic acid per kg of body weight. The ten day experimental periods were more desirable than the periods of one week. This was particularly true for the saturation period when some of the subjects had been on diets low in ascorbic acid prior to the study. / Graduation date: 1949

Thesis (M.D.S.)--University of Adelaide, Dept. of Dentistry, 1984. / Some mounted ill. Includes bibliographical references (leaves 79-101).