连续流动分析仪与自动凯氏定氮仪测定小麦秸秆全氮含量之比较

摘要

凯氏定氮法是测定植株全氮含量的经典方法,但费时费力。选择24个小麦秸秆样品,用浓 H2 SO4-H2 O2消煮,分别利用连续流动分析仪与全自动凯氏定氮仪测定消煮液中氮含量,比较了两种方法测定结果,探讨利用连续流动分析仪测定植株样品全氮含量的可行性。结果表明：两种仪器测定的小麦秸秆中全氮含量无明显差异,彼此间呈显著线性相关,回归直线方程为Y (连续流动分析仪-N)=0．892X (凯氏蒸馏滴定-N)+0．753,相关系数r=0．9421(n=24, P<0．01)。连续流动分析仪测定的回收率在96．6%~102．3%之间,对5个样品消煮液中氮浓度分别重复测定5次,相对标准偏差在5%以下。连续流动分析仪分析速度快,消耗试剂少,可用于大批量H2 SO4-H2 O2消煮的植株样品中全氮含量分析。研究结果为采用连续流动分析仪测定植株全氮含量提供了技术依据。%Kjeldahl distillation-titration has been used as a reference method for N determination in plants, but it is time consu-ming. This article aimed at establishing a time saving method for determining of plant N concentrations by continuous flow ana-lyzer ( CFA) . Twenty four of wheat plant samples were selected and digested with H2 SO4-H2 O2 . N contents in the digests were determined by CFA and an automated Kjeldahl distillation-titration ( AKDT) instrument, respectively. The test showed that there was no any significant difference of the plant N contents measured by the CFA and the AKDT method. A linear rela-tionship best described the measured N values generated by both methods: CFA-N=0. 892 AKDT-N +0. 753. The Pearson’s correlation coefficient was 0. 942 1 with a significance level (n=24, P<0. 01). The CFA method for plant N measurement had a high precision with relative standard deviation less than 5%. The standard recovery rate of feed samples with addition of ( NH4 ) 2 SO4 was 96. 6% ~102. 3%. It suggested that the CFA based on colorimetric detection of the pure ammonium chloride distillate ( Berthelot reaction) could be used to determinate N in the Kjeldahl digests of plant samples. The CFA method was labor saving and could handle large numbers of samples. The human error in mixing and other operations was reduced to a great extent.