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烟草中的尼古丁含量的测定

AN-T-175

2020-06

zh

Cost-efficient method using non-aqueous titration

尼古丁是一种含氮生物碱，对健康有害，而且非常易上瘾。烟草制品中的尼古丁含量须准确测定和指定。本应用报告介绍了一种通过非水滴定法测定烟草中尼古丁含量的简单易行的方法。与色谱法相比，滴定法是一种 “绝对法”，即在分析前无需校准系统。

Nicotine is an N-containing alkaloid that stimulates the parasympathetic nervous system, and is both highly addictive and dangerous to human health. Its toxic threshold value lies between 30–60 mg or 0.8 mg/kg, respectively. Nicotine content determination in tobacco products is therefore crucial. This Application Note exhibits an easy and straightforward method for nicotine determination in tobacco by non-aqueous titration.

Before the titration is performed, an extraction of the nicotine from tobacco is necessary. The extraction step is done using an appropriate solvent and barium chloride. Barium chloride leads to a more selective extraction of nicotine in comparison to situations in which it is not present.

Results determined by GC and IC are given as a comparison. In comparison to chromatographic methods, titration is an «absolute method», meaning it is not necessary to calibrate the system prior to the analyses.

The nicotine is extracted from ground tobacco leaves by using barium chloride and an extraction mixture containing chloroform and toluene in a ratio of 1:9.

Determinations by GC have shown that this extraction method is very selective to nicotine as only one peak appeared in the GC chromatogram.

Figure 1. Titrando system consisting of a 907 instrument in combination with tiamo.

The analyses are carried out using a 907 Titrando equipped with a Solvotrode easyClean. An aliquot of the extraction solution is transferred to a beaker, filled up with ethanol (in order to immerse the glass membrane and diaphragm of the electrode), and then titrated with standardized perchloric acid in glacial acetic acid until after the first equivalence point is reached.

Steep and smooth titration curves are obtained for all analyses.

Figure 2. Titration curve of nicotine with perchloric acid after extracting the nicotine from tobacco.
Table 1. Results of the determination of nicotine with titration, ion chromatography (IC), and gas chromatography (GC).
  n
 Mean value / % SD(abs)/ % SD(rel) /%
Titration 3 1.355 0.014 1.03
IC 1 1.41 - -
GC
 5 1.313 0.005 0.40

Nicotine is normally either determined by GC or by HPLC. The initial cost for these analytical instruments is relatively high. In comparison, titration is lower priced and affordable for nearly every laboratory. As seen in Table 1, the results between the analyses with GC and titration are comparable. Therefore, titration offers a competitive method to analyze nicotine in tobacco.

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Internal reference: AW TI CH1-1234-112016