Have you ever vaped a certain e-liquid and found it to be harsher to your throat when compared to another e-fluid? Researchers at the Portland State University have discovered that the harshness that vapers experience can be attributed to the amount of free-base nicotine in that e-liquid. Those researchers tested a novel way to establish how much free-base nicotine different brands of e-liquid had and found that the brands with the lowest free-base nicotine were the least harsh when vaped. Read the entire article in order to learn how you can use their findings to select the best e-liquids for your vaping needs.