Open-vessel microwave digestion of animal waste samples for multi-element analysis
2000
Zhang, H. | Hattey, J.A.
Wet acid digestion on a heat block or in a closed-vessel microwave digestion system normally use half a gram to 1 gram of organic samples, but it is difficult to take a small quantity of representative sample from animal waste materials due to their heterogeneity. This study investigated an alternative microwave digestion system to prepare animal manure samples for plant nutrient analysis. Two types of solid animal manure and two reference plant samples were digested with an open-vessel microwave digestion system and with the conventional nitric/perchloric acid block digestion, and analyzed for macro-and micronutrients. Results of the open-vessel microwave digested samples were comparable to those digested by conventional block digester and in high agreement with the certified values of reference materials. The open-vessel microwave can reduce digestion time from about 4 hours to about 30 minutes. Fresh samples up to 10 grams can be completely digested directly by the open-vessel microwave without sample drying and grinding. Sample representation of bulk manure should be better when sample size increased from 1 to 10 grams. Eliminating drying and grinding before digestion improves lab efficiency.
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