Extracting nicotine from tobacco can achieve the resource utilization of waste tobacco. Therefore, this article conducted a single-factor experiment to investigate the effects of process conditions (extraction time, extraction pressure, extraction temperature, CO₂ flow rate, particle size of raw materials) on the yields of nicotine and tobacco extract. In addition, using nicotine extraction rate as the indicator, extraction time, extraction pressure, extraction temperature, and CO₂ flow rate as factors, an orthogonal experiment was designed to optimize the extraction process. The composition of the obtained tobacco extract was analyzed with gas chromatography-mass spectrometry. The results show that extraction temperature has the greatest impact on nicotine extraction rate, extraction time and pressure have a relatively large impact, and CO₂ flow rate has the least impact. The optimal extraction conditions are as follows: extraction temperature is 65 ℃, extraction pressure is 22 MPa, CO₂ flow rate is 25 L/h (based on 150.0 g of tobacco raw material), extraction time is 80 minutes, and particle size is 0.60 mm. Under the optimal conditions, the nicotine extraction rate was 97.89%, and the tobacco extract yield was 5.57%. Fourteen components were detected in the volatiles of the tobacco extract, and the main components were nicotine (52.22%), neophytadiene (10.29%), and vitamin E (6.67%). Additionally, the extract also contained phytosterols, linoleic acid, and liquidambar resin, etc. Due to high nicotine content, the extract can be used as a good raw material for nicotine purification in later stages.

The physiological characteristics and behavioral patterns of infants are somewhat different from those of adults, resulting in a much higher frequency and amount of exposure to harmful chemicals than those of adults when using the same type of products. Therefore, national regulations and standards have set safety limits for harmful chemicals to protect the most vulnerable and sensitive infants. Isothiazolinone, as the common additive to improve antibacterial performance of children products, is a potential sensitizing compound that can induce allergic dermatitis. So far there is no chemical safety limit setting for it in China, while in the international existing regulations and standards, this chemical is only restricted with the total content limit. To this end, this study examined the chemical safety assessment method of infants, summarized the existing chemical safety limit model, and defined the key steps of constructing the limit model. First, dose-response data of the chemical was determined; then the dimension of the chemical limit was confirmed; after that, with the dimensional analysis method, the parameters based on product characteristics and human behavior patterns were introduced to establish the connection between the dose-response data and the chemical migration limit. On this basis, by introducing parameters of no expected sensitization inducing level, sensitization assessment factors, sweat rate and sports time, it proposed the limit model for isothiazolinones migration from children sports protection articles to sweat. Finally, the appropriate parameter values were selected based on the infant and product characteristics, and the model was applied to calculate the migration limits of the three isothiazolinones (MI, CMI and BIT) at 0.150, 0.014 and 0.150 mg/L, respectively. These migration limits are anticipated to be incorporated in the upcoming Chinese national standard Juvenile Products: General Requirements for Daily Sports Protection Articles scheduled for release by the end of 2023, which can be employed to protect of children’s skin from isothiazolinones.