Determination of oxytetracycline levels in rainbow trout serum on a biphenyl column using high-performance liquid chromatography

We developed a simple and sensitive high-performance liquid chromatography method on a biphenyl column to determine oxytetracycline (OTC) levels in rainbow trout serum. The assay used deproteination, filtration, and subsequent separation on a reverse-phase biphenyl column, with UV detection at 355 nm. OTC (7.8–7.9 min) was completely resolved from structurally similar riboflavin (10.4–10.5 min), a common feed supplement. Estimated limits of detection and quantitation of OTC were 0.01 and 0.04 μg/mL, respectively. The average recovery for OTC was 102% with a R.S.D. of 8.34%. Calibration standards were linear from 0.01 to 10 μg/mL.