Jd. Sarma et al., IMPROVED MICROBIOLOGICAL ASSAY FOR FOLIC-ACID BASED ON MICROTITER PLATING WITH STREPTOCOCCUS-FAECALIS, Journal of AOAC International, 78(5), 1995, pp. 1173-1177
We have developed an improved method, using 96-well microtiter plates,
for the microbiological assay of folic acid. With this method, the te
dium of conventional microbiological analysis is substantially decreas
ed. Culture volumes have been reduced 33-fold, and pipetting procedure
s have been simplified. Assay time has been reduced to 14 h, and sensi
tivity has increased 10-fold (0.1 ng/ml). Analytical recoveries range
from 98 to 104%. Intra-assay and interassay variabilities are less tha
n 11%. The assay does not require extensive manipulation of inoculum.
Day-to-day variability has been minimized by using saline aliquots of
the bacterial suspension stored at 4 degrees C. The procedure is accur
ate, selective, and useful for direct measurement of folic acid in mul
tivitamin formulations.