TN测定过程中空白值偏高原因分析

Discussion on Reasons for Higher Blank Value during TN Determination

TN测定过程中影响因素较多,易造成空白吸光度值偏高。针对TN空白值偏高问题,设置了无氨水类型、比色管包裹方式、碱性过硫酸钾存放条件及纯度等影响因素,进行了探究。实验结果表明:无氨水类型、包裹方式、碱性过硫酸钾存放条件对总氮测定精度造成的影响并不大;而当对碱性过硫酸钾分别重结晶一次、二次和三次后,空白吸光度值分别为1. 292、0. 033和0. 033,可见碱性过硫酸钾纯度是造成空白吸光度偏大的主要因素。

Due to many factors affecting TN measurement,the blank absorbance value is easily higher than normal.The impact factors such as ammonia free water type,package mode,alkali potassium persulfate storage condition and purity were set for studying.The results showed that the impact factors including ammonia free water type,package mode,and alkaline potassium persulfate storage had little effect on the blank absorbance value.When the alkaline potassium persulfate was used after recrystallization once,second and third,the blank absorbance values were 1.292,0.033 and 0.033.The alkali potassium persulfate purity had important effect on the blank absorbance value.