Concentrated nicotine liquid refers to a highly potent form of nicotine used in the production of e-liquids for vaping. It typically comes in higher concentrations than standard nicotine e-liquids, allowing users to achieve their desired nicotine strength with less liquid volume. Concentrated nicotine liquid is commonly diluted with other ingredients such as propylene glycol (PG) and vegetable glycerin (VG) to create e-liquids with varying nicotine strengths. It's important to handle concentrated nicotine liquid with care, as it is highly toxic in its concentrated form. Proper safety precautions should be followed, and accurate measurements are essential when mixing e-liquids to ensure the safety and consistency of the final product.