Identification of impurities in ivermectin bulk material by mass spectrometry and NMR

The identification and characterization of four process impurities in bulk ivermectin and four process impurities in bulk avermectin, using a combination of MS and NMR, are discussed herein. These process impurities were shown to be 24-demethyl H2B1a, 3′-demethyl H2B1a, 3″-demethyl H2B1a and 24a-hydroxy B2a isomer. The impurities were shown to be process impurities and are present in avermectin bulk also.