I need to spike erythromycin in wastewater for its anaerobic degradation. For this i need to prepare erythromycin stock solution. i am trying to dissolve 0.1g/100 ml of water but it's not dissolved completely even after hours of stirring.

How can i prepare 1g/L stock solution? Can i prepare stock in EtOH and then dilute it in water? I will use it in anaerobic reactor so am afraid if EtOH can affect my reactor (even if it will be in minute quantity).

Thanks