DETERMINATION OF ERYTHROMYCIN-A BY LIQUID-CHROMATOGRAPHY AND ELECTROCHEMICAL DETECTION, WITH APPLICATION TO SALMON TISSUE

The chromatographic performance of erythromycin A (EA) is improved sig nificantly over that achieved on polymeric columns by using a sterical ly shielded octyldiisopropylsilica (Zorbax Rx-C-8) column and a neutra l mobile phase consisting of 5 mM aqueous sodium perchlorate-acetonitr ile (50:50). This mobile phase facilitates electrochemical detection o f EA at the 3-pmol level. Temperature control of both column and detec tion cell is important for minimizing detector noise and drift. A clea n-up procedure, based on aminopropylsilica solid-phase extraction, all ows the detection of EA in salmon flesh down to the 0.2-ppm level. Som e of the metabolites of EA that retain the tertiary amine may also be detected by this method.