A little nicotine in tobacco leaf is non-ionized, which is also known as free-base nicotine (FBN). The dynamic equation existed between FBN and ionized nicotine can easily change with water content, temperature and pH value. In this study, a method of the direct quantitative analysis for FBN in tobacco leaf by using headspace solid-phase micro-extraction, combined with gas chromatography/mass spectrometry, was developed. The optimum conditions for analysis method, including sample forms, SPME fiber type, pre-equilibrium temperature, pre-equilibrium time, extraction temperature and extraction time, were investigated in detail. Under the optimized conditions, the linear range of the method was 1 mg/mL–100 mg/mL, with a correlation coefficient (r) of 0.9977 and a detection limit of 0.84 μg/g, the repeatability (expressed as relative standard deviation) was 3.35 %, and the recovery of this method was between 99.56 % and 99.80 %. The uncertainty budget was finally done according to the “Guide to the Expression of Uncertainty in Measurement,” and the relative expanded uncertainty was 7.1 % with coverage factor k = 2. This method may be reliable and convenient for tobacco control.

中文翻译：

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顶空固相微萃取结合气相色谱/质谱法直接分析烟叶中游离碱尼古丁

烟叶中的少量尼古丁是非电离的，也称为游离碱尼古丁（FBN）。FBN与电离尼古丁之间存在的动力学方程很容易随含水量、温度和pH值而变化。本研究建立了顶空固相微萃取结合气相色谱/质谱联用直接定量分析烟叶中FBN的方法。详细研究了分析方法的最佳条件，包括样品形式、SPME纤维类型、预平衡温度、预平衡时间、提取温度和提取时间。在优化条件下，该方法的线性范围为1 mg/mL～100 mg/mL，相关系数(r)为0.9977，检出限为0.84 μg/g，重复性（表示为相对标准偏差）为 3.35 %，该方法的回收率在 99.56 % 至 99.80 % 之间。不确定度预算最终根据《测量不确定度表达指南》进行，相对扩展不确定度为7.1%，覆盖因子k=2。这种方法对于控烟来说可能是可靠和方便的。