Studies on the determination of dissolved oxygen in water.

Studies on the decomposition rates of the Mn(III) complex of cyclohexanediaminetetra-acetate (DCTA) in light and in darkness have shown that this complex is more stable than the one derived from ethylenediaminetetra-acetate. The optimum pH range for the determination of dissolved oxygen by means of the Mn(III)-DCTA complex is found to be between 3 and 4. The absorbance of this complex is independent of the amount of DCTA used (in the range 0.2-1.0 g) with water samples containing a maximum of 3.2 ppm of dissolved oxygen. Significant interferences are caused by the presence of CO(2-)(3), HCO(-)(3), S(2)O(2-)(3), PO(3-)(4), I(-), NO(-)(2), SO(2-)(3), Ca(2+), Fe(2+) and Fe(3+) at 500 times the oxygen concentration.

Chlorination of ozonated soil fulvic acid: mutagenicity studies in Salmonella.

Samples of soil fulvic acid (SFA) were ozonated and subsequently chlorinated under acidic or slightly basic conditions. The residues were tested for His+ reversion in a fluctuation assay, using Salmonella typhimurium TA100 as the tester strain. The ozonated/chlorinated samples were mutagenic, but activity was dependent on the amount of ozone utilized and the pH of the reaction medium. Although increases in cell concentrations were also induced by some mutagenic samples, this alone did not account for the mutagenicity observed. Unchlorinated samples displayed insignificant activity.

A high pressure liquid chromatographic method for the quantitation of sub-microgram amounts of zearalenone (F-2) in agricultural products.

A highly sensitive and reliable method for the quantitation of sub-microgram quantitaties of zearalenone (F-2) residues in corn, corn oil and mixed feed is described. The isolation of this mycotoxin from a mixed solvent extract involves partitioning of the alkali soluble components from a chloroform solution, followed by acidification and extraction of organic components into chloroform, a silica gel column clean-up and analysis by high pressure liquid chromatography using a ultraviolet (UV) detector at 280 nm. The limit of detection of the instrument is shown to be 2.5 ng and that of the method is 100 ppb. The percent recoveries of zearalenone in corn is found to be 72.1 +/- 6.0 at the levels between 0.1 and 1.0 ppm, in corn oil 72.6 +/- 8.8 at levels 0.25 and 1.0 ppm and in pig starter 67.3 +/- 4.5 at 1.0 ppm level. In the case of two field samples, the reproducibility of analysis is very good and the mycotoxin contents are shown to be 11.5 +/- 0.26 and 0.61 +/- 0.07 ppm.

Bis-diazotized benzidine as a spray reagent for detecting zearalenone on thin layer chromatoplates.

Bis-diazotized benzidine is a highly sensitive spray reagent for detecting zearalenone (F-2) in corn samples. As little as 2.0 ng of this Fusarium toxin could be visualized on a thin layer plate after development. In addition, this spray reagent is more specific than the spray reagents currently used for zearalenone.

Toxicity of methylmercury: effects on different ages of rats.

LD50 of methylmercury chloride has been shown to be dependent on the ages of the rats. As the age increases, the LD50 decreases, i.e. the younger rats could tolerate higher doses of methylmercury than the older one. The LD50 were 39.6 +/- 2.3, 33.1 +/- 2.1, 30.3 +/- 1.0, 27.1 +/- 1.0, 24.7 +/- 1.5 and 23.9 +/- 1.1 mg Hg/kg for the 200 g, 300 g, 350 g, 400 g, 450 g and 500 g rates respectively. The elimination of mercury from blood showed little correspondence to age during the 30 days duration. The onset of neurological symptoms after receiving 25 mg Hg/kg of methylmercury chloride occurred between 8 to 15 days post dosing in the surviving rats. Rats unaffected during the latency period did not show neurological signs if their blood-mercury levels decreased to below 100 ppm. Young and old rats showed marked differences in the distribution of mercury in the blood. In the erythrocyte membrane, the eight week old rats retained a higher concentration of the toxic metal than did the 19.5 week old rats. Also, there was significant differences in the ratios of mercury content in the red blood cells to that of plasma; young rats showing 115:1 and for the old ones being 5:1. The permeability of erythrocyte membrane to mercury might play an important role in the age factors on the suceptibility of methylmercury intoxication.

Large scale production, purification and a study of some spectral properties of Penitrem A.

A large scale production of the tremorgenic toxin, Penitrem A, from the cultures of Penicillium (P.) palitans and P. crustosum for studying its spectral characteristics was attained. From several fermentation runs using Czapex-Dox medium, P. crustosum was shown to produce nearly 80% more toxic metabolite than P. palitans. A method involving silica-gel column chromatography for a single step isolation of the toxin from the crude extract of the mycelial mats was developed. Some spectral properties of Penitrem A were discussed.

Mutagenicity studies in Salmonella: residues of ozonated and/or chlorinated water fulvic acids.

Aqueous residues of ozonated, chlorinated, and ozonated/chlorinated water fulvic acids (WFA) were tested for induction of His+ reversion in Salmonella typhimurium strain TA100 in fluctuation tests for mutagenicity. The data suggest that ozonation of natural organics present in sources of drinking water can prevent subsequent formation of by-products of chlorination that are mutagenic in bacteria. Ozonation of the WFA at different pH and at varying dose levels produced residues that were not or were only weakly mutagenic. Chlorination of WFA or of previously ozonated WFA led to residues that were highly mutagenic. However, mutagen formation in the ozonated/chlorinated residues could be prevented, depending upon the pH of the WFA solutions during ozonation-mutagenicity decreased as pH increased. This decrease in mutagenicity is associated with previous observations of enhanced ozone decomposition into its highly reactive oxidant species at higher pH. Since ozonation seems to be more effective at alkaline pH, alkaline raw water sources seem to be the best candidates for water treatment that involves ozonation.