Determination
Reductive hydrolysis of folic acid produces 4-aminobenzoyl glutamic acid which is determined photometrically after diazotization and coupling with N-(1-naphthyl)-ethylenediamine.
In the microbiological assay, it is either by the turbidimetric growth measurement of Streptococcus faecalis ATCC 8043 or titrimetric determination of lactic acid produced by Lactobacillus casei ATCC 7469.