光谱法测定电子烟液中的游离烟碱

Spectroscopic determination of free-base nicotine in e-liquids

为快速表征电子烟液中的游离烟碱(FBN),使用可与FBN发生显色反应的指示分子——溴甲酚绿(BCG)和氯酚红(CPR),建立了电子烟液中FBN的光谱测试方法,并与pH方法和核磁共振方法进行了对比分析。结果表明:①所选择的两个指示分子为弱酸性,能够与FBN结合,而不与质子态烟碱结合,因此能够指示FBN的质量分数。②据此原理可建立光谱信号与电子烟液FBN质量分数的对应关系,使用BCG的工作曲线为lgA616=0.0172c-0.5378,r^(2)为0.9989,检测限和定量限分别为0.11和0.37 mg/g烟液;使用CPR的工作曲线为lgA587=0.0154c-0.8130,r^(2)为0.9936,检测限和定量限分别为0.19和0.63 mg/g烟液。③运用该方法测试了16个商品化烟液的FBN,实测烟液烟碱大于20 mg/g时,FBN质量百分比(αfbn)的平均值为19.2%;实测烟液烟碱小于20 mg/g时,αfbn的平均值为76.1%。低αfbn时,光谱方法测定FBN质量分数的结果比pH方法高。④光谱方法与核磁共振方法有较好的相关性,且使用CPR作为指示分子优于BCG。该方法可实现电子烟液中FBN的快速可视化判定。

In order to rapidly characterize the free-base nicotine(FBN)in e-liquids,two indicators,bromocresol green(BCG)and chlorophenol red(CPR),which could provoke color reactions with FBN,were employed to develop a spectroscopic method for FBN quantification in e-liquids.The developed method was compared with the pH method and the NMR method.The results showed that:1)The two color indicators were weakly acidic and could bind with FBN but not with protonated nicotine,thus indicating the mass fraction of FBN.2)The correlations between the spectroscopic responses and the mass fraction of FBN in e-liquids were established based on this principle.The calibration curve was lgA616=0.0172c-0.5378(r^(2)=0.9989,LOD=0.11 mg/g,LOQ=0.37 mg/g)when adopting BCG,while the calibration curve for CPR was lgA587=0.0154c-0.8130(r^(2)=0.9936,LOD=0.19 mg/g,LOQ=0.63 mg/g).3)Sixteen commercial e-liquid samples were tested using the developed method.The average proportion of FBN(αfbn)in e-liquids was 19.2%for the e-liquids with higher than 20 mg/g nicotine and 76.1%for those with lower than 20 mg/g nicotine.In addition,the mass fractions of FBN obtained by this method were higher than those by the pH method whenαfbn was lower.4)There was a good correlation between the FBN mass fractions obtained by the spectroscopic method and by the NMR method.As an indicator,CPR was better than BCG.The spectrometry method could realize the rapid and visual determination of FBN in e-liquids.