A.I.D A.N A L-Y.S- T. -S - F . O -R .. T .H ..E - . .. .. Simple Photoelectii c Signaling Device far Use with Chromatographic Columns:. William L. Porter, Eastern Regional Re.....I T.L...L.. s w c w uauurswry, Philadelphia 18;, Pa.
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HEN working with the Marvel-R:inds preparative silicic x i:d partition column (e) for the resolution of mixtures of organ ic acids, an average of ahout three frasctions an hour can bo co I.L : .. :.."---':--It.^U ~ I:WUILL~ >..1.1 L U ~ ~ C G L L u~t. lected. In practice, much time is losu to determine when it is necessary to change receivers, because inherent difficulties, such its change in flow rates due to the required changes in eluting solvents, make it impossible to employ an automatic fraction cutter. Durso, Sohall, and Whistler ( 1 ) employed a phatoelectrio circuit in their automatic fraction cutter, hut they used it to change from one solvent storage bottle to another. A simple photoelectric signaling device has been assembled in this lahoratory to indicate the approach of the end of a fraction. Use of this device saves the operator's time. Figures 1 and 2 describe the assembly of the equipment. "
The relay has a potential of 60 volts across the 20-megohm resistor in the grid circuit. Relays that do not have this potential must be used in conjunction with a battery in the phototube circuit. A harrierlayer photocell will not operate in this circuit because i t does not produce enough voltage. The light source shown in Figure 1 is a commercial microscope illuminator; hawver, a simple bulb and lens system has been used effectively.
The slit leading to the phototube is made of L/s-inch copper the ends of which are closed by soldering on mme sheet :opper and drilling '/rineh hales through bath ends.
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flows t&ough the column, a glass float moving with the meniscus
$to iosition for the next fraction and when the meniscus (flat bottom of the float) reaches the gradu&ion marking the end volume of the fraction, the receiver is ohanged. The entire sssemhlv is mounted on lsboratorv SUDDOrt rods. The phtototuhe and l&ht Eource are mounted on" do&k rc'dg to prevent their getting out of a l i m e n t during the repasiti oning of the u nit. A screw and crank mechanism can he used for a more elshorsite assembly.
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The L.mn+hnr _I.._.mishr. ...l..-l tn e v n i a o n hi..."annro-iatinn Irr ._-. in Rnlanrl Eddy and Charles Badeett of this Iaboboratorv for their helu in the design and assf!mhly of this equipment.
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LITERATURE CITED
( I ) Durso, D. F:, Sohell, E. D.. and Whistler, R. L., ANAL.C:HEM., 2:It 425 (1951). (2) Marvel. C. S.. and Rands. R. D.. Jr.. .I. Am. Chem. Sa..72, 2642 1195
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Solvent T.-, ll)llll-.l llllll.-."tend... ine I Paoer . Chromatoeranhv in Glass Cvlinders. William L. Porter, Eastern Regional Researoh Laboratory, Philadelphia 18, Pa. I _
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scribed in the literature ( 1 4 ) as the use of paper chromatography has progressed. The simple tray and tray support designed in this laboratory can be easily made in any metal shop
Figure 1. Phototuhe and Light Source as Assembled i n a Chromatographic Column
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TI Figure 2.
Diagram of Circuit for Photoelectric Signaling Device
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Figure 1. Details of Chromatographic Tray and Tray Support equipped to work with stainless steel. The assembly does not rest on the bottom of the tank, and therefore is stable, and the area under the tray is clear and unobstructed. The apparatus (Figures 1 and 2) was designed for use in a 12 X
