The influence of pH on the efficacy and residues of quinaldine

Quinaldine, an anesthetic for fish, loses its effectiveness in solutions having pH values less than 6. Measured quantities of un‐ionized quinaldine in solution compared favorably with calculated values at selected pHˈs. Quinaldine residues in largemouth bass (Micropterus salmoides) anesthetized at various pHˈs verify that only the un‐ionized portion in solution enters the fish. Quinaldine residues in fish and un‐ionized quinaldine in solution were measured by gas chromatography.