River Oder, view towards Poland
Source: BAM
Pharmaceuticals that are very important for humans, such as the broad-spectrum antibiotic amoxi-cillin (AMX), enter wastewater and thus the water cycle through our excretions as unwanted resi-dues, which could also be important with regard to the possible development of antimicrobial re-sistance. Proper accounting of residues is necessary for long-term health protection. Amoxicillin is related to the penicillins and, as a β-lactam antibiotic, tends to hydrolyse. The hydrolysis products have not yet been comprehensively evaluated in terms of their formation and effect; in particular, a long-term study of their occurrence and stability in real water samples, which influences, for ex-ample, analytical detection, was lacking.
In this work, we investigated the hydrolysis of amoxicillin at two concentrations in four different types of water (surface water (OW), mineral water (MW), drinking water (TW), ultrapure water (MQ)) under three different storage conditions over two months. The concentrations of AMX and four relevant hydrolysis products were determined using an LC-MS/MS analysis method (liquid chromatography coupled with tandem mass spectrometry).
The occurrence, relative intensity and stability of certain hydrolysis products depended more on the type of water sample than on the storage conditions. There were clear differences in the hy-drolysis rate of AMX. Hydrolysis was very slow in ultrapure water and slow in surface water, where temperature (20°C versus 4°C) had an influence, but not exposure to sunlight. In mineral water and drinking water, hydrolysis was fast to very fast. As investigations by ICP-MS (mass spectrometry with inductively coupled plasma) revealed, the main difference was that tap water and mineral water contained the metals copper (Cu2+) and zinc (Zn2+) in dissolved form, which apparently cata-lyse AMX hydrolysis. Furthermore, we were able to propose a new degradation pathway to a rela-tively stable end product of amoxicillin hydrolysis. At the same time, the catalysis of AMX degrada-tion by copper and zinc points to an effective method for the degradation of AMX under ambient conditions, which could be important in the context of the amendment of the EU Urban Wastewater Treatment Directive.
Factors affecting the hydrolysis of the antibiotic amoxicillin in the aquatic environment
Alexander Ecke, Tanja Westphalen, Anika Retzmann, Rudolf Schneider
Chemosphere 2023, Volume 311, Page 136921 et sqq.
BAM Analytical Chemistry; Reference Materials
BAM Inorganic Trace Analysis
BAM Environmental Analysis