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Sometimes, samples undergo a solvent extraction prior to ABA pretreatment to remove contaminants such as resins and waxes.A soxhlet extractor is the most common apparatus used in the extraction method.This material is non-contemporaneous and must be removed.Usually, dilute HCl (10% conc.) is used in this treatment.Upon condensing they drip down through the pyrex wool covering the sample and then through the sample itself, leaching the contaminants through the profile and dissolving them.As the pressure increases in the sample tube, the solvents are gradually deposited back into the original flask, whereupon the process is repeated.This apparatus continually recycles the solvents being used so that they do not have to be replaced.
It is then rinsed in a buchner funnel with distilled water to reduce the p H levels towards neutral.
Because HCl reacts with carbonate to produce CO2, its use in pretreatment work is restricted to non-carbonate samples.
Sodium hydroxide (Na OH) treatment is usually associated with the removal of humic acid contamination from soils, wood, charcoal and peat samples.
During this treatment, regular litmus readings are taken to determine the extent of the acidity remaining.
Once the p H level is reduced, two sample fractions are left; an acid insoluble fraction and an acid soluble fraction.