ISO issued their approval of what they stated as a “modified form of the classical technique” described by Stevenson in the textbook: Humus Chemistry, 1994.2
The method ISO outlines in their paper is, but for a few steps, identical to the LAMAR procedure.
As I read through both the ISO method and the LAMAR method to determine any differences in protocol, I make my observations as follows:
The good news is that there are no major differences between the two methods; however, some of the steps do vary by time and temperature and may be of critical difference (see table).
It appears that ISO took into account that some constituents found in humic substances, such as phenolic compounds, for example, are understood as being somewhat unstable when exposed to prolonged high temperatures or UV light.
The first difference is the time of flocculation for the HA portion. LAMAR stirs for 6 hrs. while ISO stirs for 16-18 hrs. to ensure that all the HA is flocculated.
The second major difference is the temperature of drying the HA or HFA. LAMAR drys at 90°C (194°F) while the ISO method never exceeds 65°C (149°F) during any and all of the drying steps. The rationale is that the HFA is heat labile and may degrade at 90°C (194°F).
Another difference is that after the HCl is added to flocculate the HA portion the LAMAR method lets the solution sit for 1-6 hrs., while the ISO method specifically lets the solution sit for 4 hrs. +/- 5 minutes in order to "minimize loss" of HFA.
LAMAR & ISO Objectives
The LAMAR method established an accurate and reliable way to quantify HA and FA in raw ores and products. The insoluble material is removed from the alkaline dissolved HA and FA material.
For decades, it has been difficult to accurately identify the fulvic acid portion of a humic substance without other constituents such as mineral salts, proteins, carbohydrates and mimickers of fulvic acid, such as lignosulfonates. ISO agrees with the LAMAR definition that hydrophobic fulvic acids are materials of low sulfur content containing no lignosulfates.
The ISO method identifies hydrophobic fulvic acids (HFA) as separate from humic acids (HA) derived from the raw source material. The results determine the portion of fulvic acids that tend to repel or fail to mix with water and, furthermore, distinguishes HFA from mineral salts, polysaccharides, amino sugars, amino acids, proteins, acids, and carbohydrates.
The new ISO test is very close to the LAMAR Standardized Test Method approved by the International Humic Substances Society and the AOAC. The longer time for flocculation could purify the hydrophobic fulvic acid to a greater degree. ISO’s test accounts for heat sensitivity of co-resident organic acids. The drawbacks of longer times applied in the ISO method lengthens the protocol significantly and potentially the cost. In my opinion, it is good news that the industry is embracing accurate standardized testing methods specifically for the fulvic acid fraction of humic acids.
Watch Hydrometer Test video on Fulvic Minerals with Fulvic Acid Concentration Comparison