I suggest visiting the website of the International Humic Substances Society (IHSS).  They sell standard reference materials for humic and fulvic acids from various sources recovered using standardized methods, together with comprehensive characterization data.  They also hold an international conference for leading chemists and environmental scientists in this area.  Here is the link to their HA/FA extraction procedure from organic matrices:  http://www.humicsubstances.org/soilhafa.html .  Good luck!

Dr. Nadeem,long time ago, I collected a good procedure for determination of humic acid and fulvic acid in soils.The following reference may consulted if you can access.A procedure for the characterization of soil organic matter. By Schnitzer,M and others.Can.J.Soil.Sci.61:517-519.A simple procedure by an authority on humic substances.

For my opinion, it could be done best way by shares of carbon content.

Dr. Nadeem Sarwar, I approached humic acid measurement with the extraction followed by C analysis. Please read article/book's Stevenson. Good luck

Dr. Nadeem Sarwar, I approached humic acid measurement with the extraction followed by C analysis. Please read article/book's Stevenson. Good luck

Dr. Nadeem Sarwar, I approached humic acid measurement with the extraction followed by C analysis. Please read article/book's Stevenson. Good luck

Dear colleagues, Is there any method to isolate Humic acid and fulvic acid without using any chemicals such as acid and bases?

Ultrasonic dispersion method with different powers can be tried , standardised and compared with standard methods based on bases and acids.The following reference may be consulted for information in this line.(I could not see the original).Abstract is available on researchgate.

Effect of ultrasonic power on soil organic carbon fractions (.2014) Journal of plant nutrition and soil science 177(2) DOI:10.1002/jpln201300492