MVH HUMIC ACID METHODOLOGY
Procedure for determining humic acid content
In a 2 liter volumetric flask with 500 ml of DI H2O, add 80g NaOH, 8ml ethanol and bring to volume.
STANDARD STOCK PREPARATION (1000 ppm)
Dry Humic Acid (I.H.S.S.) for 4 hours @ 105 degrees centigrade. Weigh out 0.1075 g of Humic Acid and dilute to 100 ml with extraction solution. Shake for 1 hour.
Take 5 ml of Humic Acid Standard Stock Solution and dilute to 100ml with DI H2O to make 50 ppm standard solution. Take 10 ml and dilute to 100 mIl to make 100 ppm standard. Take 20 ml and dilute to 100ml to make 200 ppm standard.
Weigh out 2g of dry sample and add sufficient extraction solution to dissolve entire sample. Mix sample well. Centrifuge an aliquot of the sample to remove any particulates. Dilute sample as necessary so it falls within the range of the standard curve.
With Spectrophotometer set at 450 nm, set up standard curve with the 50, 100 and 200 ppm standards, using water as a blank. Read your sample and calculate concentration from the standard curve.
(ppm Humic Acid from standard curve) x (dilution factor = ppm Humic Acid
% Humic Acid = ppm Humic Acid / 10,000
DTPA = Diethylenetriamine Penta Acetic Acid