The presence of tetramethylammonium
ions at pH 2 in the methanol-water mobile phase was found to minimize
column adsorption of the alkaloids resulting in decreased retention time.
Their presence also provided a high resolution separation of scopolamine
and hyoscyamine-atropine, as shown in Fig. 1. The mobile phase was
sufficiently UV-transparent for the detector to be set at 220 nm where
alkaloid absorptivity is considerably higher. Three octadecylsilane col-
umns were used, and the separation of component peaks on each column
was as good as or better than that shown.