Determination of Narasin in Raw Material, Premix, and Animal Feeds by Liquid Chromatography and Correlation to Microbiological Assay

Abstract

Abstract A method is described for the detection and quantitation of narasin in raw material, premix, and feeds by liquid chromatography (LC) and postcolumn derivatization (PCD) with vanillin. Narasin was mixed with vanillin under acidic conditions and heated, and the resulting products were measured by a variable-wavelength detector operating at 520 nm. The LC responses of narasin and narasinlike factors were determined and correlated to the microbiological response of each factor as determined with Streptococcus faecium. Narasin reference standard was characterized in the same manner as the individual factors. The chemical composition of the reference standard (i.e., the amounts of narasin factors expressed in percent) combined with the relative microbiological potency value was used to calculate the biopotency contribution of each narasin factor. A formula was used to transform chemical composition values (amounts of narasin factors expressed in percent) of the reference standard to total microbiological activity as directly obtained from the microbiological assay. The LC method was validated by analyses of raw material, premix, and cattle and poultry rations.