凱氏法
No significant differences in concentration among sub-samples were found.The certified value and uncertainty were based on the analytical results of eight labs by Kjeldahl method. 其標準值和不確定度是由多家實驗室用凱氏法進行分析測定，并經(jīng)數(shù)理統(tǒng)計處理后確定的。
