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Development and validation of a rapid method for the determination of tetracycline in activated sludge by SPE clean‐up and HPLC–UV detection

The aim of this study was to develop and validate a rapid analytical method for tetracycline (TC) determination in activated sludge. The analytical method developed is applicable on activated sludge containing a volatile suspended solid concentration below 10 g l−1, which nearly includes all wastewater treatment plants and the major proportion of membrane bioreactors. The analytical method included two steps: sample clean‐up followed by high‐performance liquid chromatography (HPLC) with ultraviolet (UV) detection analysis. Prior to the analysis, TC was extracted from the matrix by a mixture of EDTA and McIlvaine buffer. Sample clean‐up was carried out by solid phase extraction (SPE) with strong anion exchange (SAX) cartridges. SAX cartridges retained organic matters interfering with TC. Analysis was performed by HPLC–UV with a gradient elution. The method was validated as the R 2 value was 0.9991 for the calibration curve. Recoveries were between 92% (± 6%) and 103% (± 9%). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.1 mg l−1 and 0.5 mg l−1, respectively. Accuracy was not entirely satisfactory, but should be related to the complexity of the matrix, which is a hindrance to the precision of the method. The method was also validated on industrial samples.