Tail Spots Research Articles

Conditions and techniques for thin layer chromatography of aflatoxins.

AbstractSatisfactory resolution of the four common aflatoxins, B1, B2, G1 and G2, on thin layer chromatograms has been a recurring problem. The most frequently observed cause of poor resolution and tailing of spots in the chromatograms was the variable properties of the commercial silica gel‐calcium sulfate adsorbent preparations. Variations in quality were observed even from one container to the next within single lots produced by individual manufacturers. Other variables which affected the chromatography to some degree included adsorbent particle size, concentration and nature of the calcium sulfate binder, silica gel layer thickness and moisture content, vapor phase composition in the developing chamber and the solvent used for development.

The Analysis of Plasticizers by Thin Layer Chromatography

The separation of fifty kinds of plasticizers, which are widely used in Japan, was performed by thin layer chromatography, using five kinds of solvent systems and eleven kinds of coloring reagents. The tailing of spots was prevented by addition of small amount of ethyl acetate to the solvent systems. In homologous series, Rf value was increased as the carbon number of alkyl chain increased. The high molecular weight plasticizers, such as epoxidized esters, showed many spots with any of the solvent systems. For detecting the spots of every type of plasticizers, iodine chloroform reagent was effective, and other reagents showed specific coloring for each homologous plasticizers (e.g. resorcinol reagent or thymol reagent for phthalates, 2, 6-dichloroquinone-chloroimide reagent or p-nitroaniline reagent for phosphates and alkaline KMnO4 for maleates). From the results of the experiments, a mixture of unknown plasticizers could be separated and identified from Rf values with five kinds of solvent systems and the coloring reactions by several coloring reagents.

Collaborative Studies of Methods for Determining Vanillin and Ethyl Vanillin in Flavoring Material

Abstract Collaborative study was conducted on two ultraviolet absorption methods for vanillin and one paper chromatographic method for vanillin and ethyl vanillin. The official, first action screening method for vanillin was compared with another ultraviolet absorption method which determines p-hydroxybenzaldehyde. Results were more accurate by the ultraviolet absorption method than by the official method, when the estimation of p-hydroxybenzaldehyde was eliminated. The method is recommended for adoption as official, first action. Improvements have been incorporated into the paper chromatographic method to prevent tailing of spots, and the revised method is recommended for adoption as official, first action.

The Robin Does Not Change Its Tail Spots

The Robin Does Not Change Its Tail Spots

Description of a New Pipilo

Subsp. char. Terminal white spot of outer tail feather considerably shorter (less than one inch) than in megalonyx; claws much longer and heavier than in oregonus; under tail coverts darker than in atratus; rump more or less grayish, upper tail coverts tipped with pale buff. Type. No. 2274, 6, McGregor Collection, Palo Alto, California, April 9, 1898. Chord of wing 3.38; tail 3.75; exposed culmen .55; white tail spot .76; chord of hind claw 46. Collected by T. J. Hoover. Type. No. 882, Y, McGregor Collection, Palo Alto, California, March 3, 1898. Range. San Francisco Bay region. I faix + fero; sickle-bearing, referring to the large hind claw.