氨基黑10B双波长叠加吸光光度法测定烟草中微量亚硝酸根

Dw-absorptiophotometric Determination of Trace Amounts of Nitrite by its Nirosarion Reaction with Amide Black 10B

在酸性介质中,氨基黑10B的最大吸收波长为420nm,当与NO-2反应后,颜色发生变化,最大吸收峰红移,以试剂空白为参比,可观察到在525nm处有一最大吸收峰,同时在620nm处发生褪色反应,最大褪色波长和最大吸收波长处的吸光度均与溶液中NO-2的浓度成正比,其线性范围在0～20μg/25mLNO-2,摩尔吸光系数分别为ε520=1.39×104L·mol-1·cm-1,ε620=1.26×104L·mol-1·cm-1。双波长叠加法ε520+620=2.65×104L·mol-1·cm-1,相关系数为0.9998。由于显色反应在酸性介质中进行,方法具有良好的选择性,本法适于烟草中微量NO-2的测定,结果与经典的盐酸奈乙二胺比色法基本一致。

An absorption maximum at 420 nm was observed for amide black 10B in a dilute hydrochloric acid medium. When amide black 10B was reacted with NO-_~2 , the absorption maximum was shifted to 525 nm(vs. reagent blank), and simultaneously an obvious color-fading of amide black 10B was observed at 620 nm. Linear relationships between the variation of absorpances and the concentrations of nitrite ion (0~20 μg per 25 mL of solution)were obtained both at 525nm and 620nm,with molar absorptivities of ~1.39 10~4 L·mol^-1 ·cm^-1 and 1.26×10~4 L·mol^-1 ·cm^-1 respectively. By applying the method of double wavelength measurement, the molar absorptivity(ε_~525+620 )was raised to 2.65×10~4 L·mol^-1 ·cm^-1 .The correlation coefficient was found to be 0.9998. Since the reaction was carried out in an acidic medium, satisfactory selectivity was achieved. The proposed method has been used satisfactorily in the determination of NO-_~2 in tobacco samples.