Multiresidue determination of tetracycline antibiotics in propolis by using HPLC-UV detection with ultrasonic-assisted extraction and two-step solid phase extraction

An analytical method in propolis was developed and validated for the determination of four tetracyclines (TCs) by high performance liquid chromatography (HPLC) for the first time. After extraction by ultrasound, the extracting solution was subjected to Oasis HLB and weak cation-exchange cartridge to remove water-soluble and fat-soluble flavonoids, aromatic acids, terpenoid compounds, wax, and pollen debris. The calibration curves of fortified samples showed acceptable linear response (R2 > 0.99) through a range of 100–5000 ng g−1 in 20 replicates of six concentrations and the analysis of variance (ANOVA) was performed to validate the regression data. The limit of quantification of four TCs were 100 and 150 ng g−1, respectively. The recoveries of the four TCs for propolis samples spiked with 100–500 ng g−1 were in the range of 61.9–88.5% and the RSDs were between 4.80% and 13.2%. Traces of tetracycline were found in two out of 30 analysed real samples.