ANN 111: Principles of Animal Nutrition and Feed Technology (2+1)

INTRODUCTION

• Ashing is most commonly performed by burning the sample at 550 to 600^oC in a muffle furnace. As in the case of dry matter analysis, some problems can be encountered, certain minerals (e.g., Se, Pb, Cd) may be volatilized by high temperature ashing. In cases when this might be important (usually when analysis for these minerals is going to be performed) a procedure known as wet ashing is used. Wet ashing involves digestion of the organic matter with nitric and perchloric acids. This procedure, however, is quite dangerous due to the use of perchloric acid, and special precautions such as an acid fume hood are required.
• Note that total ash content is not a particularly meaningful analysis, in that it reveals nothing about specific mineral content. Moreover, ash will contain many contaminating materials like sand or soil, which may inflate a sample’s ash value. Generally, ashing is a preparatory step for further analysis of specific minerals.