Diffusion Technique for Preparing Salt Solutions, Kjeldahl Digests, and Persulfate Digests for Nitrogen-15 Analysis

摘要: When diffusion techniques are used to prepare sample for 15 N analyses, low or variable recovery is sometimes observed. The effect of on estimates enrichment unknown. Also, the suitability use with variety salt solutions and digests containing very concentrations ( 92% Of 50 μg NH 4 + -N from 75 mL 2 M NaCl, total Kjeldahl digests, KCl preserved acid. Leaving containers open 5 d after completely eliminated contamination NO 3 - by residual ; however, was inversely related length period. Recovery 0.5 K SO alkaline persulfate a 3-d period 90 77%, respectively. Complete not required obtain accurate intimates enrichment; when < 100%, method blank correction critical. mass measured in blanks blank-correct enrichments, diffused standards often had enrichments that were significantly different nondiffused standards; intimated using an isotope dilution equation, there excellent agreement between standards, regardless degree recovery.