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E R Barnhart

Publications and source records attributed to E R Barnhart.

14 recordsLinked to original sources
PubMed1996

Analytical characterization of peptide contaminants of L-tryptophan.

Reversed-phase liquid chromatographic fractions of extracts of 2 preparations of eosinophilia-myalgia syndrome (EMS)-associated L-tryptophan were analyzed by proton nuclear magnetic resonance spectrometry, mass spectrometry, microbial-growth inhibition, and amino acid residue analyses. Fraction components demonstrated properties of an antibiotic peptide resembling bacitracin. Many peptide antibiotics like bacitracin are secondary metabolites of Bacillus species, genus of the tryptophan producer organism for the implicated manufacturer. In order to determine whether a correlation exists between individual EMS cases and the concentration of peptides or bacitracin consumed, reliable methods must be developed for quantification of the total of isoforms.

Amino Acids↗
PubMed1995

Photodecomposition of 1,2,3,4- and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in water-alcohol media on a solid support.

We used a hydrophobic solid support, octadecylsilylated silica gel (C18), packed in a quartz column as a reaction medium for the photolysis of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD). When we exposed the column to a 450 W UV lamp, the adsorbed 1,2,3,4-TCDD or 2,3,7,8-TCDD in 10% 2-propanol/water decomposed completely in 20 minutes and 5 minutes, respectively. The large estimated partition coefficient of 1,2,3,4-TCDD in 10% 2-propanol/water (> 1000) indicates that on the C18 stationary phase, both the saturated hydrocarbon chains and the absorbed 2-propanol may act as proton donors and accelerate the photolysis. In direct sunlight, the adsorbed 1,2,3,4-TCDD in 10% 2-propanol/water decomposed much faster than in a nonaqueous solvent (50% 2-propanol/methanol). This solvent effect is advantageous for the practical use of the C18 photolysis process in aqueous waste treatment. We have demonstrated that complete C18 trapping with continuous photodecomposition of TCDD contained in an aqueous alcohol waste is possible.

Adsorption↗
PubMed1988

Reversed-phase liquid chromatography of the twenty-two tetrachlorodibenzo-p-dioxin isomers on pyrenylethyl- and octadecylsilylated silica gel columns.

To purify the tetrachlorobenzo-p-dioxins synthesized for chemical and biological reference standards, reversed-phase liquid chromatography on pyrenylethyl- and octadecylsilylated stationary phase (PYE and C18) columns was employed with 100% methanol. The pyrenylethyl phase satisfactorily separated isomers resulting from mixtures of reaction products which had not been adequately separated with conventional C18 or silica gel. The use of a single chromatographic mode, liquid chromatography, and a single mobile phase with columns of distinctly different properties, C18 and PYE, separates 20 of the 22 isomers from each other and from the 1246/1249 pair. (The observed properties of the two columns afford insight into steric and polarizability differences among isomers.)

Chromatography, High Pressure Liquid↗
PubMed1987

Teratogenicity of three polychlorinated dibenzofurans in C57BL/6N mice.

Polychlorinated dibenzofurans (PCDFs) are widespread environmental contaminants which have been detected in human tissues and implicated in several poisoning incidents. Their toxic effects are similar to those observed with other related halogenated aromatic hydrocarbons such as TCDD. The teratogenic effects of three PCDFs, 1,2,3,7,8-pentachlorodibenzofuran (1-PeCDF), 2,3,4,7,8-pentachlorodibenzofuran (4-PeCDF), and 1,2,3,4,7,8-hexachlorodibenzofuran (HCDF), were assessed in C57BL/6N mice. Pregnant mice were exposed on Gestation Days 10-13 to 10 ml corn oil/kg containing PCDFs. The dams were killed on Gestation Day 18 and maternal and fetal toxicity were assessed. All three compounds were highly teratogenic, with very steep and parallel dose-response curves for the two diagnostic indicators of dioxin-like teratogenicity, hydronephrosis, and cleft palate. 4-PeCDF was the most teratogenic with an ED50 of 36 micrograms/kg for cleft palate and 7 micrograms/kg for hydronephrosis. 4-PeCDF was approximately 4 times as potent as 1-PeCDF and 10 times as potent as HCDF. The teratogenic responses occurred at a dose below that where any obvious maternal or fetal toxicity was detected. Thus, these three compounds cause teratogenic responses similar to those seen with TCDD but are only 1/10 to 1/100 as potent.

Abnormalities, Drug-Induced↗