A method and system for injecting an unconcentrated sample into a receiving LC/MS/MS system that is configured to determine a concentration of one or more PFAS analytes within the unconcentrated sample, wherein the LC/MS/MS includes ESI. The unconcentrated sample may be subjected to one or more of the following ESI conditions: i) a probe gas temperature of approximately 120° C. to approximately 180° C.; ii) a sheath gas heater setting of approximately 250° C. to approximately 400° C.; and/or iii) a sheath gas flow of approximately 8 L/min to approximately 12 L/min. The unconcentrated sample's concentration and/or an injected amount of the one or more PFAS analytes is determined.