A Computer-Interfaced Drop Counter as an Inexpensive Fraction Collector for Column Chromatography

A computer-interfaced drop counter is described that serves as an inexpensive alternative to a fraction collector for column chromatography experiments. Undergraduate biochemistry laboratories frequently do not have the budget to purchase fraction collectors. Protocols that call for the manual measurement of fraction volumes as well as the manual application of buffer to the column do not provide students with the skills required to function in a professional setting. In this experiment, students use a column outfitted with Luer fittings to set up an automatic buffer-feeding system and also monitor fraction collection using a drop counter. Students have the opportunity to learn troubleshooting techniques for both methods. To illustrate this system, a sample of typical student data from an experiment in which the molecular weight of myoglobin is determined by gel filtration chromatography is shown. The system described can be used for any column chromatography experiment, including preparative gel filtration chromatography, ion exchange chromatography, and affinity chromatography. (Contains 3 figures and 2 notes.)