Tetracycline neutralizer

Hello All!

I have to set up a Suspension Time Kill (ASTM E2315) experiment to determine the antimicrobial properties of Tetracycline. I have unfortunately hit a road block. I can’t seem to inactivate Tetracycline. My team theorized that it should be inactivated once we increase the pH from pH 2 to pH 7. My first tetracycline neutralization assay was with 1% KOH (pH14), then pH 12 0.125% CaOH. I even got desperate enough to try pH 12 whole milk mixture. The results was no growth on the pH 7 Tetracycline and bacterial suspension.

I would appreciate any tips or info regarding effective Tetracycline neutralizers for a safe microbial testing (the neutralizer cannot have any negative impact on bacterial growth).