Determination of oxytetracycline in the live fish feed Artemia using high-performance liquid chromatography with ultraviolet detection.

A high-performance liquid chromatographic analytical method was developed for the determination of oxytetracycline in Artemia nauplii. A solid-phase extraction protocol was used to recover oxytetracycline and the internal standard tetracycline, from the Artemia samples. Oxytetracycline was analyzed using a 150 x 4.6 mm I.D. Hypersil-ODS column, a mobile phase of acetonitrile-tetrahydrofuran-0.01 M oxalic acid buffer (pH 3.0) (15:3:82, v/v), and an ultraviolet detection wavelength of 365 nm. The calibration curve of oxytetracycline in Artemia was linear (r2 = 0.9998) from 0.1 to 6.4 micrograms/g of tissue. Using a signal-to-noise ratio of 4:1 the oxytetracycline detection limit was 10 ng/g of tissue. Mean recovery of oxytetracycline amounted to 97%, while intra-assay variability was 1.5%. Quantitative data from an in-vivo feeding study indicated an excellent uptake of oxytetracycline by Artemia, as its levels reached 25.6 micrograms per g of nauplii.