Melchert Wanessa Roberto, Rocha Fábio R P
Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, P.O. Box 26077, 05513-970 São Paulo, SP, Brazil.
Talanta. 2005 Jan 30;65(2):461-5. doi: 10.1016/j.talanta.2004.06.022.
Nitrate determination in waters is generally carried out with cadmium filings and carcinogenic reagents or by reaction with phenolic compounds in highly concentrated sulfuric acid medium. In this work, it was developed a green analytical procedure for nitrate determination in natural waters based on direct spectrophotometric measurements in ultraviolet, using a flow-injection system with an anion-exchange column for separation of nitrate from interfering species. The proposed method employs only one reagent (HClO(4)) in a minimum amount (equivalent to 18muL concentrated acid per determination), and allowed nitrate determination within 0.50-25.0mgL(-1), without interference of up to 200.0mgL(-1) humic acid; 1.0mgL(-1) NO(2)(-); 200.0mgL(-1) PO(4)(3-); 75.0mgL(-1) Cl(-); 50.0mgL(-1) SO(4)(2-) and 15.0mgL(-1) Fe(3+). The detection limit (99.7% confidence level) and the coefficient of variation (n = 20) were estimated as 0.1mgL(-1) and 0.7%, respectively. The results obtained for natural water samples were in agreement with those achieved by the reference method based on nitrate reduction with copperized cadmium at the 95% confidence level.
水中硝酸盐的测定通常使用镉屑和致癌试剂进行，或者在高浓度硫酸介质中与酚类化合物反应。在本研究中，开发了一种用于天然水中硝酸盐测定的绿色分析方法，该方法基于紫外直接分光光度测量，使用带有阴离子交换柱的流动注射系统将硝酸盐与干扰物质分离。所提出的方法仅使用一种试剂（HClO₄），用量最少（每次测定相当于18μL浓酸），可在0.50 - 25.0mgL⁻¹范围内测定硝酸盐，不受高达200.0mgL⁻¹腐殖酸、1.0mgL⁻¹ NO₂⁻、200.0mgL⁻¹ PO₄³⁻、75.0mgL⁻¹ Cl⁻、50.0mgL⁻¹ SO₄²⁻和15.0mgL⁻¹ Fe³⁺的干扰。检测限（99.7%置信水平）和变异系数（n = 20）分别估计为0.1mgL⁻¹和0.7%。天然水样的测定结果与基于用镀铜镉还原硝酸盐的参考方法在95%置信水平下获得的结果一致。
