The ever-evolving market of electronic cigarettes (e-cigarettes) presents a challenge for analyzing and characterizing the harmful products they can produce. Earlier we reported that e-cigarette aerosols can deliver high levels of reactive free radicals; however, there are few data characterizing the production of these potentially harmful oxidants. Thus, we have performed a detailed analysis of the different parameters affecting the production of free radical by e-cigarettes. Using a temperature-controlled e-cigarette device and a novel mechanism for reliably simulating e-cigarette usage conditions, including coil activation and puff flow, we analyzed the effects of temperature, wattage, and e-liquid solvent composition of propylene glycol (PG) and glycerol (GLY) on radical production. Free radicals in e-cigarette aerosols were spin-trapped and analyzed using electron paramagnetic resonance. Free radical production increased in a temperature-dependent manner, showing a nearly 2-fold increase between 100 and 300 °C under constant-temperature conditions. Free radical production under constant wattage showed an even greater increase when going from 10 to 50 W due, in part, to higher coil temperatures compared to constant-temperature conditions. The e-liquid PG content also heavily influenced free radical production, showing a nearly 3-fold increase upon comparison of ratios of 0:100 (PG:GLY) and 100:0 (PG:GLY). Increases in PG content were also associated with increases in aerosol-induced oxidation of biologically relevant lipids. These results demonstrate that the production of reactive free radicals in e-cigarette aerosols is highly solvent dependent and increases with an increase in temperature. Radical production was somewhat dependent on aerosol production at higher temperatures; however, disproportionately high levels of free radicals were observed at ≥100 °C despite limited aerosol production. Overall, these findings suggest that e-cigarettes can be designed to minimize exposure to these potentially harmful products.

中文翻译：

---

溶剂和温度对电子烟气溶胶中自由基形成的影响

不断发展的电子烟（电子烟）市场对分析和表征其可能产生的有害产品提出了挑战。早些时候，我们报道了电子烟气雾剂可以释放出高水平的反应性自由基。但是，很少有数据可以表征这些潜在有害的氧化剂的产生。因此，我们对影响电子烟产生自由基的不同参数进行了详细分析。使用温度控制的电子烟装置和新颖的机制来可靠地模拟电子烟的使用条件，包括线圈激活和抽吸流量，我们分析了温度，瓦数和丙二醇（PG）的电子液体溶剂成分的影响和甘油（GLY）产生自由基。电子香烟气溶胶中的自由基被自旋捕获，并使用电子顺磁共振分析。自由基的产生以温度依赖性方式增加，在恒温条件下，在100至300°C之间，自由基的产生量几乎增加了2倍。在恒定功率下，自由基产生的功率从10 W上升至50 W时显示出更大的增长，部分原因是与恒温条件相比，线圈温度更高。电子液体中的PG含量也严重影响自由基的产生，在比较0：100（PG：GLY）和100：0（PG：GLY）的比率时显示出将近三倍的增长。PG含量的增加还与气溶胶诱导的生物相关脂质的氧化增加有关。这些结果表明，电子烟气溶胶中反应性自由基的产生高度依赖溶剂，并且随着温度的升高而增加。自由基的产生在某种程度上取决于更高温度下的气溶胶产生。然而，尽管气雾产生受限，但在≥100°C的条件下仍观察到过高的自由基水平。总体而言，这些发现表明，可以设计电子烟以最大程度地减少对这些潜在有害产品的接触。