Reverse phase thin layer chromatographic procedure for identification of digoxin and related fluorescing substances.

A one-step method was developed to replace the current USP monograph procedrues for identification of digoxin and determination of related fluorescing substances. The new method is much quicker than the previous tests, which required paper chromatography and fluorometric measurements, respectively. Using reverse phase silica gel plates (C18 bonded to silica gel), digoxin was separated from digitoxin, gitoxin, and digoxigenin mono-digitoxoside, and partially resolved from digoxigenin bis-digitoxoside. A digoxin reference standard is used to correlate Rf values for identification, and a dilute solution of gitoxin is also co-spotted to give a maximum intensity limit for related fluorescing substances.