I found this link, http://www.a2zproject.org/pdf/Manual_Foods.pdf

hope it will help

Microbiological analysis of the total folate contents was based on Rader et al. with a modification to the amount of the conjugase source. All procedures were

carried out under subdued light conditions. A 25 g sample of cooked legumes was homogenized in 100 ml of 0.1 M phosphate buffer (pH 7.0) and centrifuged for

30 min. A 1 ml (2 mg·ml–1) of protease (Streptomyces griseus; Sigma Chemical Co., St. Louis, MO) was added to 25 ml extract and incubated for 3 h at 37˚C. Samples were heated to 100˚C, cooled and brought to pH 7.8 with buffer. A 1 ml (20 mg·ml–1) of α-amylase (Aspergillus oryzae; Sigma Chemical Co., St. Louis, MO) was added to each extraction sample and incubated for 2 h at 37˚C.

A 4 ml (3 mg·ml–1) aliquot of chicken conjugase (Difco Laboratories, Detroit, MI) was added to each extraction sample and incubated for 16 h at 37˚C. Deconjugatedextracts were heated to 100˚C and centrifuged. The extracted

samples were appropriately diluted and used in the microbiological analysis with Lactobacillus casei subsp. Rhamnosus (ATCC No. 7469) for total folate. A

folic acid (200 µg·ml–1) standard solution was prepared according to AOAC 45.2.03 [17]. L. casei subsp. Rhamnosus was incubated for 17 h at 37˚C. Turbidimetric readings were carried out by using a spectrophotometer

(Beckman DU® 640, Fullerton, CA) at 660 nm. Each variety of cooked legumes was analyzed in triplicate. The growth response of the L. casei subsp. Rhamnosus (measure as turbidity at 660 nm) of the total folate in the sample was compared quantitatively to standard solutions of folic acid.

2.4.2. HPLC Analysis

Folate derivatives of tetrahydrofolate (THF), 5-formyltetrahydrofolate

(5-CHO-THF) and 5-methyl tetrahydrofolate (5-CH3-THF) in sample were identified and quantified by reversed-phase ion-pair HPLC with fluorometric detection after ion exchange solid phase extraction. Individual folate standards THF, 5-CHO-THF, 5-CH3-THF, folic acid were purchased from Sigma Chemical Co. (St. Louis, MO).