>99% [HPLC]. Free 4MU < 25ppm.
For detection of E. coli: P.C.S. Feng and P.A. Hartman, Appl. Environ. Microbiol., 43, 1320 (1982); B.J. Robison, Appl. Environ. Microbiol., 48, 285 (1984); R.J. Alverez, J. Food Sci., 49, 1186 (1984). In a membrane filter method: L.C. Shadix et al., Can. J. Microbiol., 39, 1066 (1993).