Nicotine, as a bioactive alkaloid, has a long history with humanity, predominantly found in tobacco plants. In recent years, however, nicotine salts have sparked interest as an innovative technology. This article aims to delve into the origins, relationship, and applications of nicotine and nicotine salts in the realm of electronic cigarettes.

I. Origins of Nicotine and Nicotine Salts

Nicotine: Nicotine is a bioactive alkaloid widely present in plants of the Solanaceae family, such as tobacco. It is an organic compound that not only exists in tobacco leaves but also in the fruits of other Solanaceae plants like potatoes, tomatoes, and goji berries. However, tobacco contains the highest concentration of nicotine. Nicotine offers effects such as enhanced focus, appetite suppression, and stress relief, providing smokers with a sense of pleasure. Yet, it also carries a certain level of addiction. Nicotine stands as one of the most crucial chemicals in tobacco. At room temperature, nicotine is a colorless, transparent, oily liquid that fully dissolves in water and alcohol. It emits a strong, distinct odor, with pure nicotine liquid exuding a typical tobacco scent. In the early stages of e-cigarettes, nicotine was directly added to the vaping liquid. This was due to nicotine's volatility, efficiently transitioning from liquid to vapor upon heating. However, nicotine's strong irritant effect on the mouth, nasal passages, and throat led to a subpar user experience, coupled with the inefficiency of nicotine absorption, hindering further growth in the e-cigarette market.

Nicotine Salts: Nicotine salts are salts composed of nicotine and acids. Despite the name, they are not salts but crystals formed through the reaction of original nicotine with organic acids. The significance of nicotine salts lies in resolving the efficiency issue of nicotine in blood circulation. In 2015, the U.S.-based company JUUL pioneered nicotine salt technology. This technology involves the reaction of nicotine with organic acids to form nicotine salts, which are then added to vaping liquids. The invention of nicotine salts allowed vapers to experience a smoother taste, aiding deeper absorption of aerosol, significantly enhancing nicotine's transmission efficiency and bodily absorption rate. Following the invention of nicotine salts, the conversion rate of e-cigarettes among American smokers increased fivefold, altering the smoking habits of 30% of American smokers. The innovation of nicotine salt technology brought new possibilities to the e-cigarette industry, providing smokers with an enhanced experience.

II. Synthesis and Application of Nicotine Salts

Synthesis of Nicotine Salts: Materials Required: Precisely weigh 473g of nicotine and 527g of citric acid. Mixing Process: At room temperature, slowly mix nicotine with citric acid to ensure thorough uniformity, resulting in a light red mixture. Reaction and Stirring: Place the mixture in a constant temperature environment at 25°C, stirring continuously at a speed of 200 rpm for 6.5 hours. Subsequently, allow it to naturally cool to room temperature, where the mixture will become clearer, obtaining the desired nicotine salts.

Production Method and Formula for E-cigarette Liquid: Formula: According to precise mass ratios, include 2-10 parts of the prepared nicotine salts, 50-100 parts of propylene glycol, 50-100 parts of vegetable glycerin, and 1-5 parts of volatile oil. Production Steps:

1. Material Weighing: Based on the formula, accurately weigh 5 parts of nicotine salts, 80 parts of propylene glycol, 80 parts of vegetable glycerin, and 3 parts of volatile oil.
2. Special Nicotine Salt Preparation: Firstly, evenly mix tartaric acid, citric acid, and malic acid in a heating stirring tank maintained at 55-85°C. Control the stirring speed at 60-80 rpm. Simultaneously, preheat ascorbic acid, glycyrrhizic acid, tartaric acid, and gallic acid. Then, sequentially add these components to the stirring tank along with nicotine, ensuring a full reaction. After the reaction, crush the solid to obtain the specially prepared nicotine salts.
3. Mixing and Dissolving: Place the mixture of propylene glycol and vegetable glycerin into the stirring tank, then add the prepared nicotine salts from step 2. Stir continuously for 1-3 hours at a temperature of 25-50°C to ensure complete dissolution. Subsequently, filter the mixture with an 80-120 mesh cloth at room temperature to obtain the pure filtered solution.
4. Flavoring and Packaging: Add an equal mix of garlic volatile oil and wild yam volatile oil to the filtered solution, stirring for 3-5 minutes for thorough blending. Finally, seal the package to complete the entire production process of e-cigarette liquid.

III. Differences Between Nicotine and Nicotine Salts:

Absorption Speed: Nicotine salts are absorbed extremely quickly, entering the bloodstream within approximately 6 seconds. This design aims to simulate the rapid nicotine stimulation experienced while smoking. The rapid absorption and metabolism of nicotine salts allow users to swiftly satisfy their cravings, reducing smoking frequency. In comparison, nicotine's absorption and accumulation processes are slower, with a slower appearance and disappearance rate of peaks.

Flavor and Throat Hit: At high concentrations, nicotine may impart a peppery, spicy taste that not only affects the overall flavor of e-liquids but can also cause throat discomfort. In contrast, due to its closer-to-neutral pH value, nicotine salts offer a milder throat hit even at high concentrations, without negatively impacting the flavor of e-liquids.

Detailed Comparison: (A visual comparison chart can be included here for better illustration.)

IV. Development Directions and Trends of Nicotine Salts

Optimization of Acids: The three most common acids used to synthesize nicotine salts are lactic acid, benzoic acid, and acetic acid. Benzoic acid is the most commonly used acid in manufacturing nicotine salts. Future technological innovations may focus on finding more suitable acids or optimizing the performance of existing acids. This includes enhancing the acid's selectivity for nicotine, improving reaction efficiency, and reducing by-products. Additionally, exploration of new acid types or catalysts may be pursued to achieve a more efficient synthesis process of nicotine salts.

Enhancement of Nicotine Salt Purity: Improving purity is a key goal in the development of nicotine salts, developing more efficient and precise separation and purification techniques to remove potential impurities and contaminants, enhancing the purity of nicotine salts. This will help smokers better adapt to e-cigarette products with low nicotine concentrations while achieving better throat hit and satisfaction under legal nicotine concentration conditions.

Composite Nicotine Salt Technology: This is an emerging research direction aimed at precise calculation and optimization of the ratio of acids to nicotine by delving into the properties of nicotine salts formed by the combination of organic acids and nicotine. The core of this technology lies in understanding the interactions between different organic acids and nicotine, and how these interactions affect the chemical properties, physical forms, and sensory experiences of nicotine salts.

In conclusion, the technological innovation directions of nicotine salts are diverse, aiming to enhance their purity, optimize flavor, improve stability, and meet the diverse needs of consumers.