Improvements in the qualitative and quantitative study of erythromycins using laser-based polarimetric detection

A technique in which liquid chromatographic separation is combined with laser-based polarimetric detection is described for the study of erythromycin and its analogs. The polarimetric system, owing to the inherent selectivity of the technique, can provide unique advantages, particularly when the measurement must be made in a complicated matrix. Individual specific rotations have been measured for the three erythromycin analogs A, B and C and for the derivative erythromycin ethylsuccinate (EES). The results suggest that specific rotation may be used to identify closely related erythromycin species in studies of their fate and location in physiological pathways. The detection limit for the technique is 12 ng for erythromycin and 10 ng for EES. The distinct advantages of this technique, in terms of both sensitivity and selectivity, are demonstrated by the determination of erythromycin in milk and EES in a pharmaceutical preparation.