Determination of water (moisture) and dry matter in animal feed, grain, and forage (plant tissue) by Karl Fischer titration: Collaborative study

Abstract

A Karl Fischer method for determining water (dry matter) in animal feed and forages was collaboratively studied. Water was extracted from animal feed or forage material into methanol-formamide (1+1) directly in the Karl Fischer titration vessel by high-speed homogenization. The water was titrated at 50°C with one-component Karl Fischer reagent based on imidazole. Ten blind samples were sent to 9 collaborators in the United States, Canada, and Germany. The within-laboratory relative standard deviation (repeatability) ranged from 1.14 to 6.99% for water or from 0.09 to 0.56% for dry matter. Among-laboratory (including within-) relative standard deviation (reproducibility) ranged from 5.35 to 10.73%, or from 0.44 to 0.77% for dry matter. The authors recommend that the method be adopted as Official First Action by AOAC INTERNATIONAL. A comparable alternative extraction procedure using boiling methanol is also recommended for Official First Action.