Determination of acid insoluble ash/ Ash Insoluble in Hydrochloric Acid

Principle
Ash insoluble in hydrochloric acid (AIA) is determined gravimetrically as the residue remaining
after boiling the ash fraction with hydrochloric acid.
Scope
This procedure is applicable for determination of ash in feed ingredients and feeds. This
method cannot be used for mineral mixtures.
Responsibilities
Laboratory Analysts shall perform the analysis as per this method. It is the responsibility
of the Laboratory Analyst to ensure that all conditions laid down in the method are met
and strictly adhered to. Any deviations from the prescribed method shall be recorded and
supervisor notified.
Equipment
4.1 Incineration dish.
4.2 Analytical electronic balance, accurate to 0.1 mg.
4.3 Muffle furnace, capable of maintaining temperatures to 550 ± 20 °C.
4.4 Desiccator.
4.5 Hot plate.
4.6 Ash-free filter paper.
4.7 Forced-air drying oven capable of maintaining temperature to 103 ± 2 °C. Oven
should be equipped with a shelf to allow circulation of air. It should be operated with
open vents.
Reagents
5.1 3 M hydrochloric acid.
Procedure
6.1 Dry incineration dish (4.1) at 103 ± 2 °C for at least 2 hours, remove from oven and
cool in a desiccator.
6.2 Weigh the empty incineration dish (4.1) to the nearest 0.1 mg (W1).
6.3 Add approximately 5 g of sample to the dish and weigh to the nearest 0.1 mg (W2).
6.4 Place the dish in preheated muffle furnace (4.3) adjusted to 550 ± 20 °C for 3 hours.
6.5 Inspect visually if the residue is free from carbonaceous particles (see remark 9.1).
6.6 Transfer dish into a desiccator (4.4) and allow to cool down to room temperature
(approximately 45 minutes).
6.7 Transfer the ash quantitatively to a beaker using 75 ml 3 M hydrochloric acid (5.1).
6.8 Heat the mixture on a hot plate (4.5) carefully to boiling, and boil for 15 minutes.
6.9 Filter the mixture through ash-free filter paper (4.6) and wash with hot distilled water
until the washings are free from acid.
6.10 Transfer the filter paper with the residue to an incineration dish.
6.11 Dry the incineration dish overnight in drying oven (4.7) adjusted to 103 ± 2 °C.
6.12 Place the dish in preheated muffle furnace (4.3) adjusted to 550 ± 20 °C for 2 hours.
6.13 Transfer dish into a desiccator (4.4) and allow to cool to room temperature (approximately
45 minutes).
6.14 Weigh the dish and the residue to the nearest 0.1 mg (W3)
Calculation
Percent AIA (% AIA)
% AIA = (W3 – W1) x 100 / (W2 – W1)
where,
W1 = weight of empty dish (g),
W2 = weight of the dish and sample (g), and
W3 = weight of dish and residue after incineration (g).