A gravimetric Kjeldahl—precautions and improved procedures

A variety of wheat (Triticum aestivum L. cv. Vona) tissues were analyzed with three tube diffusion Kjeldahl procedures yielding quantitative recovery of N in 2 days, 1 day, and 18 h employing gravimetric detection. Recoveries of wheat N by the gravimetric Kjeldahl procedures averaged 2.01% higher than by steam distillation and standard acid titration. Absolute gravimetric determinations on 3-mg N standards yielded N recoveries of 99.86%, 99.69%, and 98.46% for 2-day, 18-h, and 1-day diffusion respectively, whereas steam distillation of 1-mg N standards yielded an average recovery of 97.69%. The gravimetric Kjeldahl procedures are preferably applied to samples containing at least 3 mg N.