Ash Analysis

Abstract

Ashing is an important first step in proximate or specific mineral analysis. Ash refers to the inorganic (mineral) residue remaining after the combustion or complete acid-facilitated oxidation of organic matter in food. This chapter covers the instrumentation, principles, procedures, advantages, and disadvantages various ashing procedures. The two major types of ashing analysis, dry ashing and wet ashing, can be accomplished by conventional means or by the use of microwave systems. The procedure of choice depends upon the use of the ash following its determination, and limitations based on cost, time, and sample numbers. Conventional dry ashing is based upon sample incineration at high temperatures (500-600°C) in a muffle furnace. Wet ashing (acid-facilitated oxidation) is often used as a preparation for specific elemental analysis by atomic absorption, inductively coupled plasma, and/or mass spectrometry. Microwave ashing (dry or wet) is faster than conventional methods and requires little additional equipment or space, but sample throughput may be a limiting factor.