Carboxylated Polystyrene Particles for Plastic Standards in Laser Ablation ICP–MS Trace Elements Analysis: Analytical Aspects and Environmental Relevance

Reliable quantification of trace metals in polymers by direct solid-state analysis remains limited by the lack of suitable reference materials. In this study, we introduce a novel method for producing standardized plastic samples specifically designed for the calibration and analysis of trace metals by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Carboxylated polystyrene (PS) nanoparticles, capable of adsorbing metal ions from solution, were synthesized and evaluated. The trace metal adsorption capabilities of these PS nanoparticles were assessed with adsorption isotherms fit well with the Freundlich model. The study focused cobalt (Co²⁺), copper (Cu²⁺), and lead (Pb²⁺) The adsorption constants were found to be 0.15 for Co²⁺, 0.48 for Cu²⁺, and 3.63 for Pb²⁺. The metal-sorbed PS nanoparticles were then processed into disc-shaped plastics via hot-press molding, and LA-ICP-MS analysis confirmed the homogeneous metal distribution both at the surface and in depth, with relative standard deviations (RSD) of less than 5% for all metals analyzed. Calibration curves for Pb²⁺ (1220-4400 mg kg^-1), Cu²⁺ (210-600 mg kg^-1), and Co²⁺ (67-220 mg kg^-1) showed strong linear relationships, with <i>R</i> ² values of 0.96 for Pb²⁺, 0.95 for Cu²⁺, and 0.94 for Co²⁺. The methodology limits of detection (LOD) were determined to be 113 mg kg^-1 for Pb²⁺, 93 mg kg^-1 for Cu²⁺, and 23 mg kg^-1 for Co²⁺. The developed standards enabled the calibration of analytical instruments and thus improve the reliability of assessments concerning the contamination of environments with metal-laden microplastics.