Determination of ozonation rate constants for lincomycin and spectinomycin

Recent occurrences of pharmaceutical antibiotics in surface water, drinking water, and wastewater systems have gained significant attention due to their potential threats to human health. This study determined the absolute second-order rate constants of ozone with two amine-based antibiotics, namely, lincomycin and spectinomycin, using the stopped-flow technique under controlled ionic strength, buffer, and temperature. Results indicate that ozone reacts quickly with the selected antibiotics, and the reaction rate significantly depends on solution pH. For lincomycin, ozone attacks its free amine group and sulfur group with absolute rate constants of 2.76 x 10(6) M-1.s(-1) (for neutral form) and 3.26 x 10(5) M-1.s(-1) (for monoprotonated form), respectively. For spectinomycin, ozone attacks two free amine groups with absolute rate constants of 1.27 x 10(6) M-1.s(-1) (for neutral form) and 3.30 x 10(5) M-1.s(-1) (for monoprotonated form), respectively. These rate constants have been corrected to zero ionic strength. Protonated amine is nonreactive toward ozone. Model prediction indicates that lincomycin and spectinomycin can be effectively transformed by ozonation processes around neutral pH.