The development of the chemistry for solid-phase oligonucleotide synthesis has enabled its widespread use in molecular biology laboratories for construction of novel linkers, site-directed mutagenesis, and many other techniques. The material obtained from a particular synthesis contains traces of premature termination products and other unwanted byproducts of the organic reactions. For most uses in genetic engineering, the material must be purified free of these contaminants. The most efficient method is undoubtedly by HPLC or FPLC, but in circumstances in which these systems are not available, the method described below provides very pure oligonucleotides in reasonable yield. The method described here is based loosely on that described by Narang et al. (1 ) and on information supplied by Applied Biosystems (oligonucleotide synthesis is described in Chapters 13 and 14 ).
