Author(s) :

Woojoo Park, Kayla Ahn, Leah Jin, Kelly Kim, Hannah Lee, Elin Huh.

Volume/Issue :

Abstract :

Methylene blue (MB) is a cationic dye widely used in biological, chemical, and medical applications. Its reduced form, leucomethylene blue (LMB), is electrically neutral following a proton-coupled electron transfer reaction. Ascorbic acid is commonly used as the electron donor, while hydrochloric acid (HCl) supplies the protons required for reduction. However, the high corrosivity of HCl raises safety and handling concerns. This study investigated benzalkonium chloride (BKC), a quaternary ammonium compound, as a potential non-acidic alternative to HCl in the MB reduction system. Solutions containing 0%, 1%, 5%, 10%, and 20% (v/v) BKC were evaluated. Increasing the BKC concentration generally decreased the final absorbance, with the 20% (v/v) BKC condition producing the lowest final absorbance among the BKC groups. However, the HCl–ascorbic acid control reached a stable absorbance plateau more rapidly than any BKC condition, while the 20% BKC condition required a longer time than the 5% and 10% BKC conditions despite producing the lowest final absorbance. These findings suggest that BKC may serve as a safer alternative to HCl when a greater overall extent of MB reduction is desired, although it does not match the reaction rate of the conventional HCl–ascorbic acid system.