Nitrate und Nitrite

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Nitrate und Nitrite

Analytical and Bioanalytical Chemistry -     

Nitrite und Nitrate

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Neue Reaktionen der Nitrate und Nitrite

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Neue Reaktionen der Nitrate und Nitrite

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Nachweis und Bestimmung der Nitrate und Nitrite im Trinkwasser

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Nitrate and Nitrite Ultraviolet Actinometers

Abstract We developed nitrate and nitrite actinometers to determine radiant fluxes from 290 to 410 nm. These actinometers are based on the reaction of the photochemically generated OH radical with benzoic acid to form salicylic acid (SA) and p-hydroxybenzoic acid (pHBA). Actinom-eter development included determination of the temperature and wavelength dependence of the quantum yield for formation of SA and pHBA from nitrate and nitrite photolysis in air-saturated solutions. Quantum yields (at 25°C) for SA production from nitrate photolysis ranged from 0.00146 to 0.00418 between 290 and 350 nm, and from 0.00185 to 0.00633 for nitrite photolysis between 290 and 405 nm. The quantum yields for SA production were approximately 50–60% greater than quantum yields for pHBA production from nitrate and nitrite photolysis. For both actinometers, SA and pHBA formation was temperature dependent, increasing by approximately a factor of 2.2 from 0 to 35°C. Activation energies for SA formation varied with wavelength, ranging from 14.7 to 16.5 kj mol -¹ between 290 and 330 nm for the nitrate actinometer and 12.3 to 17.8 kj mol-¹ between 310 and 390 nm for the nitrite actinometer. Activation energies for pHBA formation were 2–11% higher. Wavelength-dependent changes in the quantum yield and activation energy for SA and pHBA formation from nitrate photolysis suggest multiple electronic transitions for nitrate from 290 to 350 nm. Quantum yields for OH radical formation from nitrate and nitrite photolyses were estimated from SA and pHBA quantum yields at 25°C. Wavelength-dependent OH quantum yields ranged from 0.007 to 0.014 for nitrate photolysis between 290 and 330 nm and from 0.024 to 0.078 for nitrite photolysis between 298 and 390 nm. The nitrate and nitrite actinometers can maintain initial rate conditions for hours, are insensitive to laboratory lighting, easy to use and extremely sensitive; the minimum radiant energy that can be detected in our irradiation system is approximately 10^-9 einsteins.     

Flow Injection Biamperometric Determination of Nitrite and Nitrate

Abstract

A simple and efficient FIA method was used with good results to determine nitrite in residual waters and nitrate in natural waters. Nitrite determination is based on the reaction with iodide occurring in acidic medium and biamperometric detection of the formed iodine at two platinum electrodes polarised at a potential of 100 mV. Nitrate is similarly determined after its previous reduction to nitrite in a cadmium column. The method does not need the solution deaeration. However, the calibration graphs present two regions of linearity owing to the catalytic effect of the dissolved oxygen on the iodide oxidation by nitrite.     

快速测定水样中的硝酸盐和亚硝酸盐

1 引言 测定硝酸盐的常用比色法有酚二磺酸法和紫外双波长法，但这两者都有一定的缺陷。N-（1-萘基）-乙二胺盐酸盐光度法是一种测定亚硝酸盐的简便、准确的方法，为国内外普遍采用。由于亚硝酸盐和硝酸盐在近紫外区的吸收光谱有重叠而影响硝酸盐在紫外区的测定。去除亚硝酸盐干扰的方法有2种，一种是通过加入氨基磺酸来消除，另一种是先测出亚硝酸盐的浓度，通过校正曲线算出它在紫外区的吸光度，再从总吸光度中扣除，其中后一种方法更合理。但笔者依据后一种思想测定硝酸盐和亚硝酸盐的混合溶液中的硝酸盐含量都较理论值低，而通过多元线性回归方程计算的硝酸盐值比单独用硝酸盐标准曲线计算的结果更好。     

荧光动力学光度法同时测定硝酸根及亚硝酸根的研究

基于亚硝根对溴酸钾氧化罗丹明６Ｇ的催化及锌粉使硝酸根还原为亚硝酸根的原理，建立了同时测定亚硝酸根和硝酸根的荧光动力学法，用于饮用水、质控水样、饮料中硝酸根及亚硝酸根的测定，测定下限分别为０．０７４ｎｇＮＯ２＾－／ｍｌ和０．２５ｎｇＮＯ３＾－／ｍｌ。     

导数-三波长光度法同时测定肉制品中亚硝酸盐和硝酸盐的研究

本文提出了导数三波长光度法同时测定NO_2~-和NO_3~-显色化合物的新方法,并利用自编程序完成测定,操作简单快速。该法直接测定NO_2~-和NO_3~-与间苯二酚在浓H_2SO_4介质中生成的有色产物,它们均在0～14μg/10ml范围内服从比耳定律,其表观摩尔吸收系数△εNO_3~-为8.28×10~2L·mol~(-1)·cm~(-1)和△εNO_2~-为3.85×10~3L·mol~(-1)·cm~(-1)。应用该法对市售熟牛肉和午餐肉进行了分析,获得满意结果。     

乙二胺合钴溶液中亚硝酸盐和硝酸盐氮的测定

建立了快速测定乙二胺合钴溶液中亚硝酸和硝酸盐的方法。使用麝香草酚法测定硝酸盐,使用改进了的GB 13580.7-92测定亚硝酸盐。硝酸盐的线性范围在8 mg·L-1以内,亚硝酸盐的线性范围为0.03~0.8 mg·L-1,相关系数分别为0.999 9,0.999 4。硝酸盐的加标回收率在99.9%~108%之间,测定值的相对标准偏差(n=7)为1.2%;亚硝酸盐的加标回收率在99.5%~107%之间,测定值的相对标准偏差(n=7)为1.4%。     

离子色谱法测定水果中亚硝酸盐和硝酸盐

建立了离子色谱法测定水果中亚硝酸盐和硝酸盐的方法.试样溶液中亚硝酸盐和硝酸盐在YSA-8阴离子色谱柱分离,以4 mmol.L-1碳酸钠-3 mmol.L-1碳酸氢钠为流动相,电导检测.亚硝酸盐和硝酸盐的检出限分别为0.02 mg·L-1和0.11 mg·L-1,工作曲线的线性范围分别在0.2～20.0 mg·L-1和0.3～30.0 mg·L-1范围内.该方法已应用于水果中亚硝酸盐和硝酸盐的测定,测得回收率在93.4%～105.2%之间.