Carlson M P, Schneider N R
J Assoc Off Anal Chem. 1986 Mar-Apr;69(2):196-8.
Each of 10 collaborating laboratories analyzed 4 blind duplicate pairs of forage samples for nitrate, by using a potentiometric method. Two forage controls and a 100 000 mg KNO3/L standard were also provided. Nitrate was extracted into an aqueous Al2(SO4)3 solution containing 70 mg KNO3/L and quantitated with a nitrate-selective electrode. Standards were prepared using extracting solution as diluent. Nitrate concentrations in forage samples ranged from less than 0.50 to 4.35% KNO3. Repeatability coefficients of variation (CVo) ranged from 1.74 to 3.61%, and reproducibility coefficients of variation (CVx) ranged from 6.92 to 7.66%. Mean recovery of a 0.55% KNO3 spike was 94.5%. The method has been adopted official first action.
10个合作实验室分别采用电位滴定法对4对盲样饲草样品进行了硝酸盐分析。同时还提供了两种饲草对照品和一种100000mg KNO₃/L的标准品。硝酸盐被萃取到含有70mg KNO₃/L的Al₂(SO₄)₃水溶液中，并用硝酸盐选择性电极进行定量分析。标准品用萃取液作为稀释剂配制。饲草样品中的硝酸盐浓度范围为小于0.50%至4.35% KNO₃。重复性变异系数（CVo）范围为1.74%至3.61%，再现性变异系数（CVx）范围为6.92%至7.66%。0.55% KNO₃加标回收率平均为94.5%。该方法已被采用为官方首次行动方法。
