Analyzes of β-lactam antibiotics by direct injection of environmental water samples into a functionalized graphene oxide-silica packed capillary extraction column online coupled to liquid chromatography tandem mass spectrometry

An environmentally friendly and high-throughput method for monitoring β-lactam antibiotics in environmental water samples is presented. In this study, an in-lab synthesized graphene oxide supported onto aminopropyl silica (GO@SiO₂) sorbent was packed inside a fused silica capillary to produce a miniaturized extraction column. The main goal was to develop a greener analytical method that requires low amounts of chemicals to be executed and, consequently, generates a reduced volume of toxic waste. To achieve that, the GO@SiO₂ extraction column was online coupled with a LC-MS/MS instrument to carry out an automated and miniaturized sample preparation step before analytical quantification. A chemometric optimization was performed considering the variables possibly affecting the analytical performance: sample loading flow, sample loading time, and temperature of analysis. Under optimized conditions, the method reported good analysis times (12 min) and consumed fewer reagents compared to other publications on the same topic. Important validation parameters were evaluated accordingly with the ICH Q2(R1) validation guideline. The method showed appropriate linearity between 1 – 100 μg/L (R² > 0.99), as well as LODs (S/N = 3) in the range of 0.2 – 0.3 μg/L. Accuracy, intra- and inter-day precision (RSD%) were in acceptable ranges between 82.3 – 107.1%, and 0.8 – 20.6%, respectively. Out of ten collected environmental water samples, two reported the presence of cefalexin. Ultimately, the method was demonstrated to be fast, environmentally friendly, and reliable for monitoring the β-lactams. Therefore, it represents an excellent alternative to still widely-used and non-miniaturized methods based on time-consuming sample preparation.