Long-Term Chemical and Virucidal Stability of Multi-Component Veterinary Disinfectants: Relationships Between Active Ingredient Content and Virucidal Efficacy

Long-term stability of veterinary disinfectants depends not only on the preservation of active-ingredient content but also on the maintenance of biological efficacy. This study evaluated the 24-month real-time chemical and virucidal stability of five powder formulations (powder F1–F5) containing potassium peroxymonosulfate (PPMS) and malic acid (MA) and five liquid formulations (liquid F1–F5) containing benzalkonium chloride (BZK) and citric acid (CA). At six storage time points (months 0, 3, 6, 12, 18, and 24), active-ingredient contents were quantified and virucidal efficacy against modified vaccinia virus Ankara (MVA) was assessed at 25-, 100-, and 300-fold dilutions. Associations between remaining active-ingredient content and virucidal efficacy were analyzed using repeated-measures correlation. In the powder formulations, PPMS and MA contents progressively decreased during storage, accompanied by corresponding reductions in virucidal efficacy, with strong positive correlations between remaining content and efficacy. In contrast, BZK and CA contents in the liquid formulations remained relatively stable, whereas virucidal efficacy declined substantially in several formulations, showing weaker content–efficacy associations. The F1 formulations, representing composition ratios commonly used in commercial disinfectants, showed different stability patterns: powder F1 exhibited comparatively favorable efficacy retention, whereas liquid F1 maintained efficacy near its initial level through month 18 but declined markedly by month 24. These findings demonstrate that chemical and functional stability may diverge during prolonged storage and support consideration of biological efficacy testing as a complementary measure to active-ingredient analysis under the conditions investigated.