Nitrocefin is the chromogenic cephalosporin that acts as an excellent β-lactamase substrate. It exhibits a rapid distinctive color change from yellow (max at pH 7.0 = 390 nm) to red (max at pH 7.0 = 486 nm) as the amide bond in the beta-lactam ring is hydrolyzed by a β-lactamase. It is sensitive to hydrolysis by all known lactamases produced by Gram-positive and Gram-negative bacteria. MW: 516.5. Purity ≥95% by UV