Atsunobu Yoda
Kobe University, Mikage Branch Kobe, Japan
A Self-controlling Apparatus for Column Chromatography under Pressure
W h e n pressure is applied to control the flow rate in column chromatography, it is often troublesome to ensure that the column does not become dry during the stepwise elution. The self-controlling apparatus here described eliminates this trouble and allows the elution solvent to be changed automatically. The thermal conductivity of a gas affects the electrical resistance of a thermistor, but there is a great difference in the thermal conductivity between the gas
and the liquid. Accordmgly, it is possible to measure the thermistor resistance and to detect whether a liquid level is above or below a thermistor. This principle is used in this self-controlling apparatus. As shown in Figure 1,a U-type column is used. The pressure in the reservoir is elevated by closing valve 1 (Fig. 3) operated by relay B. When valve 1 is opened, the pressure is released and the column does not run dry. The detecting thermistor (TA)' is placed just above the upper end of the column. By circuit 1 (Fig. 2), relay A is released when there is temperature difference between TA, covered by solvent, and the compensating thermistor (TB), placed in the air near the column. The relay is operated when TA is exposed to the air. The control of valve 1 by relay A is stabilized by the delay circuit, circuit 2 (Fig. 2). By the modification of this self-stopping apparatus as shown in Figure 4, it is possible to supply another solvent automatically. Reservoir 2 is connected with reservoir 1 by a siphon and with a pressure system LA "Ten Thermistor," type KD-27 (Kobe Kogyo Co., Kobe Japan) was placed in a thin-walled glass tube containing a little Silicone oil. Solenoid
Self-dopping system d the column chromatography under R: rolvent reservoir; TA: detecting thermistor; C: column; V-1; valve 1. ~i~~~~ 1.
-2 PRESSURE SYSTEM
I A.C. I I O V
Circuit-2
Circuit-3 Figure 2. Circuit system of the thermistor control. A: reloy A; 8: relay B (controls valves 1 and 2); C: relay C; . ; breok contact of reioy A; b: break contoct of relay B; c; break contact of reloy C; TA: deteding thermistor Idkc type, about 2 0 0 ohms); TB; compensating thermistor (identical with TAI; V-1: 6AU6; V-2: T Y 6 6 G llhyratron, Tokyo Shibovro Co, Kawaroki, Japan); V-3: 7 6 ; V-4: RMC40 (thermal reloy, Nippon Electric Co.,Tokyol.
Figure 4. Self-controlling system of fhe column chromatography. R-1: re9ervoir 1; R-2: reservoir 2; TA: delecling thermistor; C: coivmn; V-2: valve 2; pressure system: the same or in Fig. 1.
Volume 41, Number
4,April 7964 / 217
by valve 2, which is operated by relay B when valve 1 is closed. When TA is dipped in the solvent, the same positive pressure is applied in both reservoirs, and the solvent transfer from reservoir 2 to reservoir 1 does not occur because valve 1 closes and valve 2 opens. However, when the reservoir 1 becomes empty (when TA is exposed), valve 1 is opened and valve 2 is closed. The solvent in reservoir 2 flows down
21 8 / Journal of Chemical Education
through the siphon because the pressure decreases only in reservoir 1. As a result, TA is covered again and valve 1is closed. Circuit 3 (Fig. 2) will cut off both circuits 1 and 2 when the elution is completed. If the electricity supply were cut off in the midst of the elution, the pressure would be released without the solvent transfer from reservoir 2 to reservoir 1.
