160 / 172
Conclusions
The AOAC Official Methods 959.03 (Urease Method) and 983.01 (HPLC Method) are frequently
inaccurate and therefore not suitable for measuring the amounts of free and unreacted urea in liquid
urea-formaldehyde condensate products. AOAC Official Method 2003.14 consistently provides more
accurate analytical results for measuring the contents of free urea in these classes of fertilizers.
Acknowledgements
We give special thanks to Hugh Rodriguez, Thornton Laboratory, Tampa, FL, and John Hartshorn, Morral
Chemical Co., Morral, OH, for collaborative support of this study. We are also indebted to Nancy Thiex
and James Bartos for many helpful suggestions.