Elemental Composition of Denim Samples via Conductive Heating-Assisted Decomposition with Low Acid Consumption and ICP-OES Detection

This study aimed to determine the elemental composition (Al, Co, Cu, Mg, Mn, Ni, and Zn) of denim garments with varying compositions. An acid digestion method was developed using a 2³ full factorial design to optimize sample preparation conditions, using an open-system digester block. Among 29 denim samples, 27 were successfully digested, exhibiting residual carbon and acidity below 2% and 10%, respectively. Elemental analysis was conducted using ICP OES, with validation through recovery tests (75-125%) and a certified reference material. No significant differences were found between the determined and certified values, as confirmed by a <i>t</i> test. DLS analysis revealed a particle size distribution of less than 1 μm in the digested samples. The method proved to be cost-effective, also reducing acid use by up to 80% compared to previous works. Additionally, the method attained an analytical Eco-Scale score of 83, thereby qualifying as an excellent example of green analytical methodology. While Mg showed the highest concentration (322.2 mg kg^-1), the elements Co (0.34 mg kg^-1) and Ni (0.67 mg kg^-1) exhibited the lowest concentrations. Cu and Mn were found in concentrations higher than recommended levels (50 mg kg^-1 for Cu and 90 mg kg^-1 for Mn), with ranges of 0.07 to 89.3 mg kg^-1 Cu and 1.4 to 608.0 mg kg^-1 Mn. On the other hand, Ni concentrations were close to the established limit (1 mg kg^-1 Ni), ranging from 0.57 to 1.0 mg kg^-1. These findings underscore the need for additional research on denim to identify toxic elements and their associated health risks.