Positive Pressure for Column Chromatography During the course of an NSF "Student Originated Studies'' project a problem developed in a critical separation step of the analysis procedure for pentachlorophenol. This problem arose due to the small mesh size (200-400) of ion-exchange resin used in a reservoir top glass chromatographic column. During the elution procedure the bottom of the packed column lost liquid and "channeling" could be clearly observed. The students involved consulted with the faculty advisor concerning this problem. As a consequence, a relatively inexpensive battery operated portable aeration pump of the type usually sold for keeping live minnows during fishing trips was adapted quite easily to the column. The air stone which comes with the pump assembly was removed from the end of the attached tubing. The tubing was then connected directly t o a glass tube in a rubber stopper as shown. Several brands of aquarium pumps including some powered by 115 V ac were tried, but the one which we found to he the mast satisfactory was the portable ''Seaway" brand. Over an 8-wk period six of these pumps operated about 20 hr/wk each without failure except for an occasional battery replacement. BY using these, two major problems were eliminated. Channeling a t the bottom of the column was stopped and the elution time was cut from a two hour operation to a one hour operation. Howard P. Williams Donald H. Moore Vaxx Allen Uyrd University of Southern Mississippi Hattiesburg, Mississippi 39401
370
/
Journal o f Chemical Education
