The vaping and electronic cigarette industries have grown impressively in the past decade. Usage among youths has increased from around 1% in 2011 to 10.5–27.5% in 2019 (pre-teens vs. older teenagers) mainly due to the vast array of flavor options available (Truth Initiative, 2020). The mixtures used in these products are usually called «e-liquid», «e-fluid», or «e-juice». To ensure the quality of these e-liquids, testing the most important quality parameters is required. One important quality control parameter is the nicotine content available in these products.

Nicotine in tobacco is usually determined by gas chromatography or liquid chromatography. Aqueous acid base titration is a much more affordable alternative for this determination. As e-liquids do not contain other components which might interfere with the titration, the aqueous acid base titration presented in this Application Note can be applied for nicotine determination.

This method is an affordable and reliable way to determine the nicotine content in e-liquids and their nicotine starting material, ensuring the quality of these products.

Nicotine starting material for e-liquids as well as e-liquids are analyzed. No sample preparation is required.

Titration system consisting of a 905 Titrando, a rod stirrer, and a Unitrode easyClean. The data are recorded and evaluated by tiamo.
Figure 1. Titration system consisting of a 905 Titrando, a rod stirrer, and a Unitrode easyClean. The data are recorded and evaluated by tiamo.

The analyses are carried out on a 905 Titrando system with a rod stirrer and a Unitrode easyClean for indication of the equivalence point.

A suitable amount of sample is transferred into a disposable beaker and deionized water is added. The solution is stirred to ensure complete dissolution and mixing. Afterwards, the solution is titrated with standardized hydrochloric acid until after the first equivalence point is reached.

Steep and smooth titration curves are obtained for all analyses. An example titration curve is displayed in Figure 2. The automated analysis leads to reproducible results with low RSDs as shown in Table 1.

Table 1. Results of the nicotine determination by aqueous titration in nicotine starting materials as well as in various e-liquids (n = 3).
  Mean value / g/L SD(abs) / g/L SD(rel) /%
Nicotine starting material 31.39 0.01 0.03
E-liquid 1 5.64 0.01 0.24
E-liquid 2 2.82 0.001 0.04
E-liquid 3 15.32 0.08 0.53
E-liquid 4 10.15 0.04 0.35
Figure 2. Example titration curve for the nicotine determination in an e-liquid.

This method is an affordable and reliable way to determine the nicotine content in e-liquids and their nicotine starting material, ensuring the quality of these products. Additionally, no harmful chemicals and no sample preparation are required for the determination.

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