Preparation of Gel and Buffer

Most applications of ImEl have been realized with commercial forms of agar. Difco Bacto Agar from Difco Laboratories, Detroit, Mich., 

is very useful other products of Difco— Special Agar Noble and Difco Purified Agar —come close to maximum purification. The product of Merck A. G., Darmstadt, Germany (Agar-agar, pulv. subst.) 

Grabar and Williams (G5) have developed the following procedure for purification of the commercial product. Agar is dissolved by boiling in distilled water when a 6 % sol is attained, it is poured into wide trays after setting, the gel is cut into small blocks these are extracted for 2 days in distilled water, which is renewed 5 times. The gel is now perfectly white and is kept in stoppered sterile containers. In order to eliminate organic substances, Wieme (W4) extracts the gel with 50 % ethanol in distilled water. An exacting method of purification (Bl) uses electrodialysis. 

All these techniques tend to lower the ionality of the agar gel the rigidity is thereby increased, whereas the intensity of the electroosmotic flow is decreased. It follows that results with ImEl are comparable only if identical conditions have prevailed during the foregoing purification. The following stock buffer solutions have an ionic strength of t/2 = 0.1 (W4) when the specified quantities of constituents are made up to 1 liter with distilled water (plus 0.5 g sodium azide). 

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