Constructing a limit model and developing an HPLC-MS/MS analytical method for measuring isothiazolinone migration from children's sports protectors into sweat

Infants and children have certain differences in physiological characteristics and behavioral patterns compared with adults, resulting in significantly higher exposure frequency and amounts to harmful chemical substances than those of adults when using similar products. To ensure the chemical safety of children when using sports protectors, we established a sweat migration limit model for isothiazolinones. Through this model, we determined the migration limits for MI, CMI and BIT to be 0.15 mg L⁻¹, 0.014 mg L⁻¹ and 0.15 mg L⁻¹, respectively. Furthermore, a corresponding isothiazolinone sweat migration detection method was established. The experiment focused on the influences of artificial sweat composition, pH value, and oscillation frequency and time on migration, ensuring that the pre-treatment migration process could restore the contact scene between the skin and the lining of the children's sports protectors and ensure sufficient migration efficiency. The experimental results showed that the three isothiazolinones exhibited linearity within a concentration range of 0.010–0.500 mg L⁻¹, with correlation coefficients (R²) exceeding 0.9990; the quantification limits of the method were 0.7–3.0 μg, which meets the requirements of the migration limits of the three isothiazolinones. The recoveries of the method are within the range of 87.2–114.8% with RSDs below 10%, and the RSDs of the intra-day precision and inter-day precision were less than 8%. The accuracy and precision of the method were between 87.2% and 114.8%, and the RSDs of intra-day and inter-day precision were below 8%. The accuracy and precision of the method meet the daily testing requirements. Different from the traditional isothiazolinone detection method, the method established in this study detects the migration amount of isothiazolinones rather than their total content in the samples, which is believed to be more scientific and efficient in protecting the skin health of infants and children.