Reversed-phase high-performance liquid chromatography of the cardiac glycoside LNF-209 with refractive index...

LNF-209 is a glycoside, similar to digoxin, which has potential for use in the treatment of congestive heart failure. However, unlike digoxin it exhibits virtually no useful UV absorption spectra, making detection difficult. One means of detection is the refractive index detector, but like most bulk property detectors it has certain limitations. Its sensitivity is limited and it is sensitive to small changes in a number of parameters, such as temperature, mobile phase composition, and flow-rate. These parameters must be closely controlled to obtain a stable baseline. This paper describes the steps taken to control the system and the development and validation of an assay for LNF-209 in dosing solutions. The method developed is capable of quantitating LNF-209 in solutions of sterile water and 5% dextrose at concentrations ranging from 8 to 6000 micrograms/ml. The method is linear over this range and quantitative recovery is obtained. The overall average relative standard deviation for replicate analysis of several samples at various concentrations assayed over two days was 2.3%.