Investigation of Continuous Flow Methods for Determining the Content of Reducing Sugar in Tobacco *

SUMMARY Reducing sugar in tobacco can reduce the pungent odor of cigarette smoke and is the important indicator of tobacco routine chemical analysis. In order to improve the stability of the continuous flow method for the determination of the reducing sugar content in tobacco, the current ISO method, ISO 15154:2003, was intentionally modified as follows: the 5% acetic acid solution in the blue/blue pipeline was replaced by 0.2 mol@L-1 hydrochloric acid solution in the red/red pipeline; the concentration of sodium hydroxide was reduced from 0.5 mol@L-1 to 0.4 mol@L-1; and the volume of the heating tank was increased from 7.7 mL to 10.6 mL. It was found that the repeatability and reproducibility of the revised method kept comparable to those of ISO 15154:2003, the effective sampling in one experiment of the revised method was increased to 90 cups without precipitates in the pipeline, the main reaction time was extended by 45 s, and the lifespan of the heating tank was prolonged by more than 100%. In addition, the modified method was evaluated via a general validation procedure, and the detection limit and the quantitation limit were 0.0057% and 0.0190%, respectively. Furthermore, the relative standard deviation was less than 5%, and the recovery of added standard was between 98.22% and 103.65%. These results indicate that the modified method is a promising alternative to the current ISO method. [Contrib. Tob. Nicotine Res. 32 (2023) 11–17]