Delay Circuit for Fraction Collection of Very Volatile Liquids W. H. Bancroft, Jr., Medical Research, Veterans Administration Hospital, Birmingham, Ala.
wo problems encountered in the
T chromatography of volatile samples are (1) evaporation when a drop count fraction collector is used, and (2) differing ratcs of collection when a preset time collector is used. To alleviate these problems an intermittent calibrated siphon may he used in conjunction with :I. delay circuit in series with the drop rounter. With the counter set a t a few drops, this system allows ample time for emptying the siphon. This delay circuit was designed to hc used with a Technicon drop count fraction collector, so that the lead from the counter may simply be plugged into the delay circuit, which is connccted to the fraction collector. Thc delay circuit is composed of a thermaltype delay relay which activates a power relay to energize the fraction collector. The system has been used suc-
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cessfullJ-for many months at this laboratory.
As the siphon empties, the drop counter set a t about 3 drops activates the delay circuit. As the siphon takes approximatcly 30 seconds to empty, the delay must be of longer duration. A 3-minute delay tube was employed.
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Because of the chattering when cnnt:rct is made, a thermal relay cannot hc connected to an inductive load without gcncrating excessive voltages for the relay. Therefore, i t was connected to a of larger current capaeity. After the prescribed delay, the poiver rclay closes, causing the fraction c.nllector to bring a new collector tube into place.
Glass Paper Chromatography of the Long-chain Fatty Acids, Brominated Derivatives, and Methyl Esters Robert L. Ory, W. G. Bickford, and J. W. Dieckert, Southern Regional Research Laborator/, U. S. Department of Agriculture, N e w Orleans, Lo.
(5) separation of the H methyl polybromostearates on alnOWTON’S’
mina and silicic acid columns suggested that glass paper chromatography might he useful for the separation of these substances. The present investigation mas designed to test the above idea and to extend the knowledge of how various classes of organic compounds behave under conditions of glass paper chromatography.
hroniine in ether or Skellysolve at -10’ C. in the absence of sunlight. Methyl esters of the fatty acids and their bromine derivatives were prepared by treatment with diazomethane. Methyl esters made from authentic samples of tetra- and hexahromostearic acids served as standard reference compounds.
EXPERIMENTAL
Glass paper impregnated with silicic acid (2). Glass paper impregnated with alumina (1). For each kind of treated paper 4 X 7 inch sheets were used. PREPARATION OF POLYBROMOSTEARITES. The fatty acids were bromintited a t the double bonds by adding
b Figure 1. Typical chromatogram showing separation of saturated and unsaturated fatty acids os brominated methyl esters Solvent, 100% iro-octane A. Methyl palmitote B. Melhyl oleate C. Mixture of A, B, D, E, and F
D. E.
F.
Methyl dibrornorteorate Methyl tetrabromortearate Methyl hexabrornortearote
CHROXATOGRAPHY. The general technique was that of Dieckert and Reiser (4)as modified by Dieckert and Morris (S). All solvents were used IT-ithout further purification. The chromatographed substances were made visible in the usual manner by treatmetit n.ith concentrated sulfuric acid plus heat. Each fatty acid was applied in 5- to 10.~1. quantities in 0.05% solutions of each component. Table I. Chromatography of Fatty Acids on Glass Paper Impregnated with Silicic Acid Ri Values
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MisSiihstance S l o n e tiire” Methyl Esters of Brominated and Unbrominated Acids 0.82 0.83 Methyl palmitate Methyl oleate 0.78 n.83 Methyl dihromosteamte 0.62 0.66 Mcthyl tetrahromostearate 0.47 0.50 Methyl hexnLmmostearate 0 . 2 3 0.44 Frce Fatty Acids and ‘l’heii Bromine Derivatives Oleic acid 0.53b I)ihromostesric acid 0.w Tctrabromostearic acid 0 ,:w Hcxsbromostearic acid 0.27fi a Solvent, 100% isa-octane. 1, Average values. Solvent, 2”’, ethyl ether in iso-octane.
VOL. 31, NO. 8, AUGUST 1959
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