水杨酸钠紫外分光光度法测定烟草中的总氮

建立水杨酸钠紫外分光光度法测定烟草中总氮含量的方法。烟草样品经硫酸铜–硫酸钾–浓硫酸消化,用水杨酸钠–二氯异氰尿酸钠显色后用紫外分光光度计检测,并对波长、显色剂用量和反应时间等实验条件进行了优化。总氮的质量浓度在5~60 mg/L范围内与其吸光度呈良好的线性关系,线性相关系数为0.998 8,方法的检出限为0.14 mg/L。样品分析结果的相对标准偏差为3.22%(n=6),样品加标回收率为99.30%~101.62%。该方法具有较高的精密度和准确度,尤其适用于样品量少时对烟草中总氮的测定。

Determination of Total Nitrogen in Tobacco by Sodium Salicylic Ultraviolet Spectrophotometry

A method was established for the determination of total nitrogen in tobacco and its products by salicylic acid and sodium hypochlorite spectrophotometry. The tobacco samples were digested with copper sulfate, potassium sulphate and concentrated sulfuric acid, and were examined with sodium salicylate and sodium dichloroisocyanurate, and then detected by ultraviolet spectrophotometer. The experimental conditions such as the wavelength, the dosage of chromogenic agent and the reaction time were optimized. The mass concentration of total nitrogen had good linear relationship with ultraviolet absorbance in the range of 5-60 mg/L, and the correlation coefficient was 0.998 8, the detection limit was 0.14 mg/L. The relative standard deviation of determination results was 3.22 %(n=6), and the recovery rate was 99.30%-101.62%. The method has high precision and accuracy, and it is especially suitable for the determination of total nitrogen in tobacco when the amount of samples is small.