Because of her interest in nutrition and nutrients, Coward was one of the early adopters of chromatography following its introduction in 1906-1911 by M. S. Tswett.
Carotenoids, a class of structurally similar pigment molecules that include carotenes and xanthophylls, were of particular interest in nutritional research due to their demonstrated importance in animal studies. In his pioneering chromatographic research, Tswett showed the presence of four different xanthophylls in his studies of plant extracts, separated through the use of adsorption chromatography. Following L. S. Palmers descriptions of Tswetts experiment in 1922, Coward replicated the methodology, the results of which she published in 1923. During these studies Coward noted the presence of additional pigment (which would later be determined to be carotenes) in the eluent fractions, nearly developing a chromatographic method for the isolation of vitamin A from the carotenoids. This experiment made her the fifth scientist to adopt the use of chromatography, during a "dormant" period before the techniques popularization in the 1930s.
This early research applying adsorption chromatography would continue in her role at the Royal Pharmaceutical Society, in conjunction with other analytical methods.