In High-Performance Liquid Chromatography (HPLC), the choice of sample vial material directly influences the accuracy and reliability of analytical results. Polypropylene (PP) and glass are two predominant materials used for HPLC vials, each exhibiting distinct characteristics in terms of chemical compatibility, solvent resistance, and physical stability. This white paper presents a systematic comparison of these materials based on laboratory tests and industry data, aiming to assist researchers and laboratory managers in making informed decisions.