Ferree M A, Shannon R D
249 Agricultural Engineering Building, Pennsylvania State University, University Park, PA 16802, USA.
Water Res. 2001 Jan;35(1):327-32. doi: 10.1016/s0043-1354(00)00222-0.
A method for nitrate analysis based on second derivative UV/Visible spectroscopy was developed by Simal et al. (1985: Simal J., Lage M. A., and Iglesias I. (1985) Second derivative ultraviolet spectroscopy and sulfamic acid method for determination of nitrates in water. J. Assoc. Analyt. Chem. 68, 962-964) and Suzuki and Kuroda (1987: Suzuki, N. and Kuroda R. (1987) Direct simultaneous determination of nitrate and nitrite by ultraviolet second-derivative spectrophotometry. Analyst 112, 1077-1079), and later modified for the analysis of total nitrogen in aqueous samples of varying nitrate:organic nitrogen ratios (Crumpton et al., 1992: Crumption W. G., Isenhart T. M. and Mitchell P. D. (1992) Nitrate and organic N analyses with second-derivative spectroscopy. Limnol. Oceanogr. 37, 907-913). The procedure uses the second derivative of the absorption spectrum for nitrate (NO3-), which has a peak at approximately 224 nm that is proportional to the NO3- concentration. Samples for total N analysis are first oxidized to NO3- by persulfate digestion. The objectives of this study were to: (1) test the accuracy and precision of the second derivative method through the use of NIST-traceable wastewater check samples; (2) determine whether the second derivative method for nitrate analysis can be used for wastewater samples and whether the method compares favorably with other currently used nitrate analysis methods; and (3) use the method to analyze wastewater samples containing a range of nitrate and total nitrogen concentrations. Our results indicated that the method needed to be modified to include a longer digestion time (60 min) and dilution of samples prior to digestion (if needed). With the modified method, nitrogen recoveries were not significantly different (P > or = 0.05) from samples with known N concentrations. In addition, nitrate concentrations in constructed wetland and wastewater samples analyzed by both second derivative spectroscopy and ion chromatography were not significantly different. Total nitrogen concentrations in wastewater samples also compared favorably to the same samples analyzed by Kjeldahl digestion. The method is faster, simpler, requires smaller sample volumes, and generates less waste than many EPA-approved methods of N analysis, and may offer a suitable alternative to current methods for analysis of nitrate and total N in wastewater samples.
西马尔等人（1985年：西马尔J.、拉赫M. A.和伊格莱西亚斯I.（1985年）用二阶导数紫外光谱法和氨基磺酸法测定水中硝酸盐。《分析化学协会杂志》68，962 - 964）以及铃木和黑田（1987年：铃木N.和黑田R.（1987年）用紫外二阶导数分光光度法直接同时测定硝酸盐和亚硝酸盐。《分析家》112，1077 - 1079）开发了一种基于二阶导数紫外/可见光谱法的硝酸盐分析方法，后来该方法针对不同硝酸盐：有机氮比例的水样中总氮的分析进行了改进（克伦普顿等人，1992年：克伦普顿W. G.、伊森哈特T. M.和米切尔P. D.（1992年）用二阶导数光谱法分析硝酸盐和有机氮。《湖沼学与海洋学》37，907 - 913）。该程序使用硝酸盐（NO3-）吸收光谱的二阶导数，其在约224 nm处有一个峰值，该峰值与NO3-浓度成正比。用于总氮分析的样品首先通过过硫酸盐消解氧化为NO3-。本研究的目的是：（1）通过使用可溯源至美国国家标准与技术研究院的废水对照样品来测试二阶导数法的准确性和精密度；（2）确定用于硝酸盐分析的二阶导数法是否可用于废水样品，以及该方法与其他当前使用的硝酸盐分析方法相比是否具有优势；（3）使用该方法分析含有一系列硝酸盐和总氮浓度的废水样品。我们的结果表明，该方法需要改进，包括延长消解时间（60分钟）以及在消解前对样品进行稀释（如有需要）。采用改进后的方法，氮回收率与已知氮浓度的样品相比无显著差异（P≥0.05）。此外，通过二阶导数光谱法和离子色谱法分析的人工湿地和废水样品中的硝酸盐浓度无显著差异。废水样品中的总氮浓度与通过凯氏定氮法分析的相同样品相比也具有优势。该方法比许多美国环境保护局批准的氮分析方法更快、更简单，所需样品体积更小，产生的废物更少，并且可能为当前废水样品中硝酸盐和总氮的分析方法提供合适的替代方案。
