Effect of ampicillin-sulbactam on clinical capillary zone electrophoresis of serum proteins.

BACKGROUND: Capillary zone electrophoresis (CZE) is a well-accepted automated method used to separate serum proteins and detect monoclonal components. CZE uses ultraviolet detection at 214 nm to directly quantify proteins via peptide bonds. Any substance that absorbs at 214 nm and is present in serum can potentially interfere with CZE analysis. This has been reported for radio-contrast media and antibiotics. METHODS: Here we describe a peak on the anode side of the alpha(2)-globulin fraction caused by the antibiotic ampicillin-sulbactam (Unacid). RESULTS AND CONCLUSIONS: Extra peaks that can be misinterpreted as monoclonal components can be present in almost all electrophoretic fractions of CZE. Immunosubtraction or immunofixation is always required to rule out these conditions.