Zatar N A, Abu-Eid M A, Eid A F
Chemistry Department, An-Najah N. University, Nablus, Palestine, Israel.
Talanta. 1999 Nov 15;50(4):819-26. doi: 10.1016/s0039-9140(99)00152-6.
A method for spectrophotometric determination of nitrite and nitrate is described. This method is based on the reduction of phosphomolybdic acid to phosphomolybdenum blue complex by sodium sulfide. The obtained phosphomolybdenum blue complex is oxidized by the addition of nitrite and this causes a reduction in intensity of the blue color. The absolute decrease in the absorbance of the blue color or the rate of its decrease is found to be directly proportional to the amount of nitrite added. The absorbance of the phosphomolybdenum blue complex is monitored spectrophotometrically at 814 nm and related to the concentration of nitrite present. The effect of different factors such as acidity, stability of the complex, time, temperature, phosphate concentration, molybdenum concentration, sodium sulfide concentration and the tolerance amount of other ions have been reported. Maximum absorbance is at 814 nm. The range of linearity using the conventional method is 0.5-2.0 ppm with molar absorptivity of 1.1 x 10(4) l mol(-1) cm(-1). and a relative standard deviation of 2.6% for five measurements. The range of linearity using the reaction rate method is 0.2-3.6 ppm with a relative standard deviation of 2.4% for five measurements. The method is applied for determination of nitrite and nitrate in water, meat products and vegetables.
描述了一种分光光度法测定亚硝酸盐和硝酸盐的方法。该方法基于硫化钠将磷钼酸还原为磷钼蓝络合物。加入亚硝酸盐会氧化所得到的磷钼蓝络合物，这会导致蓝色强度降低。发现蓝色吸光度的绝对降低或其降低速率与加入的亚硝酸盐量成正比。在814nm处用分光光度法监测磷钼蓝络合物的吸光度，并与存在的亚硝酸盐浓度相关。报道了不同因素如酸度、络合物稳定性、时间、温度、磷酸盐浓度、钼浓度、硫化钠浓度以及其他离子的耐受量的影响。最大吸光度在814nm处。使用传统方法的线性范围是0.5 - 2.0ppm，摩尔吸光系数为1.1×10(4) l mol(-1) cm(-1)，五次测量的相对标准偏差为2.6%。使用反应速率法的线性范围是0.2 - 3.6ppm，五次测量的相对标准偏差为2.4%。该方法用于测定水、肉类产品和蔬菜中的亚硝酸盐和硝酸盐。
