E-liquid, often called vape juice, is the fluid formulated for use in electronic nicotine delivery systems (ENDS). This specialized liquid is heated to produce an inhalable aerosol, commonly but inaccurately referred to as vapor. Its primary function is to serve as a carrier for flavorings and, typically, nicotine, transforming these components into a mist for the user to breathe in. E-liquid consists of four main ingredients that determine the overall user experience, including the intensity of the throat sensation and the density of the visible cloud.
The Core Chemical Components
The base of nearly all e-liquids is a mixture of two primary diluents: Propylene Glycol (PG) and Vegetable Glycerin (VG). Propylene Glycol is a thin, synthetic liquid that efficiently carries flavor and provides a physical sensation in the throat, often called “throat hit.” Because of its low viscosity, PG is easily absorbed by the heating element, making higher-PG liquids favored in smaller, lower-power devices.
Vegetable Glycerin (VG), in contrast, is a thicker, slightly sweet liquid derived from plant oils. VG is responsible for producing the dense, visible aerosol cloud, meaning higher VG ratios yield larger clouds. Its inherent sweetness contributes a smoother, milder sensation upon inhalation, counteracting the sharpness of high-nicotine or high-PG formulations. Most e-liquids blend PG and VG in various ratios to balance flavor intensity, throat sensation, and cloud size.
The remaining components are flavorings and nicotine, if the liquid is not designated as zero-nicotine. Flavorings are a complex mixture of food-grade chemicals that impart the desired taste profile, such as fruit, dessert, or tobacco. Nicotine is the addictive substance suspended in the PG/VG base, and its concentration determines the product’s strength.
How E-Liquid Becomes Vapor
The transformation of e-liquid into an inhalable aerosol is a physical process achieved through rapid heating within the electronic device. The device contains a reservoir and a wick, typically cotton, that draws the liquid into the heating chamber via capillary action. This saturated wick is wrapped around a metal coil, known as the atomizer or heating element.
When the user activates the device, the battery sends electrical current to the coil, causing it to heat up quickly, typically ranging from 100°C to 250°C. This heat causes the PG, VG, and other components to rapidly aerosolize, converting them into a fine suspension of liquid droplets and gases. The resulting cloud is an aerosol, not a true vapor, as it contains tiny particles of the original liquid constituents. This process is distinct from the combustion that occurs in traditional cigarettes.
Understanding Nicotine Formulation and Strength
Nicotine is delivered in e-liquids in measured concentrations, typically expressed in milligrams per milliliter (mg/mL) or as a percentage. Strengths generally range from 0 mg/mL for non-nicotine options, up to 50 mg/mL in specialized formulations. The type of nicotine used significantly impacts the sensation experienced by the user.
The standard form is freebase nicotine, which is nicotine in its purest state and is naturally alkaline, giving it a high pH level. This high alkalinity results in a noticeable “throat hit,” which becomes harsher and more irritating at higher concentrations. This generally limits its comfortable use to strengths below 18 mg/mL. Freebase nicotine is also absorbed into the bloodstream at a relatively slower rate compared to nicotine salt.
The alternative is nicotine salt, or “nic salt,” which chemically modifies freebase nicotine by adding an organic acid, most commonly benzoic acid. The addition of this acid lowers the pH of the solution, making it less alkaline and smoother to inhale, even at high concentrations like 50 mg/mL. This modification allows for the delivery of higher nicotine doses without the harsh throat irritation associated with freebase. Nicotine salts are also absorbed into the bloodstream more quickly, mirroring the rapid nicotine delivery of a traditional cigarette.
Safe Storage and Handling Practices
E-liquid requires careful handling and storage because liquid nicotine is highly toxic upon ingestion or direct skin contact. Accidental exposure, particularly in children and pets, can lead to serious poisoning. Always store e-liquid in its original container, which is typically equipped with a child-resistant cap, and ensure the cap is securely fastened after each use.
To maintain the chemical integrity of the liquid, it should be kept in a cool, dark environment, ideally at room temperature, away from direct sunlight and heat sources. Exposure to heat, light, and air accelerates the oxidation of nicotine and can degrade the flavor compounds, affecting product quality. Storage locations must be elevated and locked, completely out of the sight and reach of children and household animals.
If e-liquid is spilled onto the skin, the area should be washed immediately with soap and water to prevent nicotine absorption. Proper disposal of empty e-liquid containers is also necessary, as residual nicotine can still pose a hazard. Empty bottles should be secured before being discarded to prevent access by children or pets.