Norman S. Radin

The preparative isolation of lecithin.

Publisher Summary This chapter discusses the preparative isolation of lecithin. Lecithin has generally been purified with alumina columns, but many methods have utilized silica gel columns. A nice feature of alumina is that, the flow is faster and a nontoxic solvent can be used, whereas silica gel columns have been eluted with mixtures of chloroform and methanol. The entire effluent, including the liquid between the alumina particles, is collected and evaporated under vacuum to a small volume. The remaining ethanol is removed by adding several portions of cyclohexane, each time followed by further evaporation to a small volume. The lecithin solution obtained is evaporated under vacuum to a small volume and transferred to a small weighed flask with some cyclohexane and the remaining hexane and isopropanol are then displaced as by a few evaporations with cyclohexane. The residual cyclohexane and water are removed by lyophilization, and the fluffy white lecithin is weighed to determine the yield.

A computer program for selecting animals for control and experimental groups in biochemical studies

The standard method for selecting experimental animals for control and experimental groups is by a randomization process in which each animal is placed into one of the groups without looking at any of its individual differences. An alternative, active matching process is proposed by which three to five animals are chosen to form experimental units that are closely matched with respect to average weight and with respect to distribution of weights (standard distribution values). Several such units are then randomly assigned to each control or treatment group and, at the end of the experiment, the animals within each unit are pooled prior to analysis. The merits of this approach and a computer algorithm for making the selections are described.