Analysis of Humic Acid (Final Version)

8/22/2019 Analysis of Humic Acid (Final Version)

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By

Dr. Muammad Afzal


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Humic acid

Humic acid is a principal component of humic substances, which are the majororganicconstituents of soil (humus),peat, coal, many upland streams, dystrophic lakes, and ocean

water.[1] It is produced by biodegradation of dead organic matter. It is not a single acid; rather, it

is a complex mixture of many different acids containing carboxyl andphenolate groups so that

the mixture behaves functionally as a dibasic acid or, occasionally, as a tribasic acid. Humic

acids can form complexes with ions that are commonly found in the environment creating humic

colloids. Humic and fulvic acids (fulvic acids are humic acids of lower molecular weight and

higher oxygen content than other humic acids) are commonly used as a soil supplement in

agriculture, and less commonly as a human nutritional supplement. As a nutrition supplement,

fulvic acid can be found in a liquid form as a component of mineral colloids. Fulvic acids are

poly-electrolytes and are unique colloids that diffuse easily through membranes whereas all other

colloids do not[citation needed]

. "Synthesis of fulvic acid (1a) was accomplished by a route involving

selective ozonization of 9-propenylpyranobenzopyran (1c), obtained by a regioselective

cyclization of the 2-methylsulphinylmethyl 1,3-dione(3c)."[2]


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Chemical characteristics of humic substances

Example of a typical humic acid, having a variety of components including quinone, phenol,

catechol and sugar moieties[1]

A typical humic substance is a mixture of many molecules, some of which are based on a motif

ofaromatic nuclei withphenolic and carboxylic substituents, linked together; the illustration

shows a typical structure. The functional groups that contribute most to surface charge and

reactivity of humic substances are phenolic and carboxylic groups.


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Benefits of adding Humic Acid to the soil

Increases the CEC (nutrient holding capacity) of the soil.

Increases the water holding capacity or retention ability of the soil. Improves fertilizer utilization, by preventing fertilizers from leaching

out from the root zone.

Improves the growth of various groups of beneficial micro-

organisms. Helps reduce soil erosion by increasing cohesive forces of very fine

soil particles.

Buffers pH problems, allowing plants to survive until the pH can be

corrected.

Increases and enlarges root systems and promotes plant cell

division.

Changes the physical and mechanical properties of the soil in

structure, color, and consistency.


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Increases the permeability of plant

membranes, promotes more efficient nutrient

uptake.

Aids in correcting plant chlorosis.

Increases the germination capacity of seed

Helps plants grow better in high salt

situations.

Helps intensify the Enzyme systems increasing

the metabolic changes inside the plant's cells.

Releases various types of auxins responsiblefor plant growth.

As an organic catalyst it helps speed up the

rate of chemical reactions within the plant


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Humic acid is not a fertilizer, but instead

a compliment to fertilizer. Fertilizer is anutrient source for both plants and

microflora. Humic acid essentially helps

move micronutrients from soil to plant.Its benefits have been proven both

experimentally and in the field


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Figure 1. Oxidized humic acid molecule. The organic

structure of humic acid is naturally oxidized, as shown by

the asterisks, giving it a negative charge. Positive ions,attracted to broken bonds at the site of the oxidation,

create sites for micronutrients and microflora to attach.


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STANDARD TEST METHOD FOR

HUMIC ACID


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PRINCIPLE

Particulate/colloidal matter in humic acid

sample is removed by dissolving in extraction

solution. Actual humic acid contents are

calculated gravimetrically by acid precipitation

of humic acid.


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REAGENTS/CHEMICALS

Concentrated Nitric Acid

Sodium hydroxide

Ethanol

Diethylenetriamine Pentaacetic acid (DTPA)

Humic Acid Standard (Aldrich) 93% approx.

Extraction solution (Dissolve 2g NaOH ,20ml

Ethanol and 4ml of 0.001M DTPA in 1 literdeionized water)


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METHODOLOGY

Grind humic acid sample and pass through

sieve (mesh No 100). Care should be takenthat all the sample taken for grinding mustpass through sieve to obtain homogeneoussample.

Weigh accurately 0.5 g grinded sample in100 ml volumetric flask. In case of liquidsample take 5mL after filtration.

Make volume up to mark with extractionsolution. Shake for 1hour on mechanical

shaker.


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Filter the solution through whatman No. 42 toremove the colloidal/particulate matter.

Add concentrated HNO3 until the pH reaches to 1and stay for 2hrs. Humic acid will precipitate.

Collect the precipitates by filtration throughWhatman 42 filter paper.

CALCULATIONS

Humic Acid (%) = weight of oven dry precipitates x 100weight of sample taken


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REFERENCE / RELATED DOCUMENTS

F.J. Stevenson,J. Environ. Quality, 1972,1, 333.

A.K. Fataftah, PhD Thesis, Northeastern

University, Boston, 1997.

T. L. Senn and A. R. Kingman,A Review ofHumus and Humic Acid Research

www.humates.com/methodology.html
http://www.humates.com/methodology.htmlhttp://www.humates.com/methodology.html

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Analysis of Humic Acid (Final Version)