Standard peptide purification conditions are used to purify PNAs. A reversed phase C-18 column, 100-180 Angstrom pore size and 5~10¥ìm particle size, works well. A shallow gradient of 0.5% to 1% per minute of acetonitrile as the organic phase eluent in water is typically used. For best performance, 0.1% TFA is added to both the aqueous and organic phases.