Determination of Chlorination Disinfection By-products on Healthcare Environmental Surfaces by Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry

Chlorine-based disinfectants are standard for environmental-surface disinfection in healthcare facilities, yet their reaction with organic residues generates disinfection by-products (DBPs) whose occurrence, levels, and occupational relevance on hospital surfaces remain uncharacterized. Key gaps are the lack of a validated method and baseline data, the unresolved origin of surface N-nitrosamines, and the unknown influence of chlorine, temperature, humidity, and pre-cleaning on the surface DBP signal. We developed an isotope-dilution wipe-sampling, solid-phase extraction, and ultra-performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) method for eight priority DBPs, applied it to 125 wipe samples from five departments across three campuses of a tertiary hospital in Wenzhou, and complemented field work with stainless-steel coupon experiments. Validation gave r ≥ 0.999, detection limits of 0.8–3.8 pg/cm², and recoveries of 78.4%–96.8%; field detection and quantification frequencies were 87.2% (95% CI 80.2–92.0%) and 69.6% (95% CI 61.1–77.0%), with operating rooms showing the highest total load (Kruskal–Wallis H(4) = 27.86, P < 0.001) though no pairwise contrast survived Bonferroni correction. In coupon experiments the net signal rose with chlorine and temperature but not humidity, with an unexplained chlorine-dependent increment (≈55% at 2000 mg/L) reflecting analytical signal behavior rather than verified formation chemistry, and pre-cleaning reduced haloacetic acids and chlorophenols by 35–55% but N-nitrosamines by only 3–9%. These results provide the first isotope-dilution baseline of DBP loads on healthcare surfaces, a reproducible monitoring method, and occurrence data for revising disinfection and occupational-hygiene standards, and they identify precursor-controlled formation experiments, biological monitoring, and direct testing of medical rubber as next steps.