Determination of cysteamine in animal feeds by high performance liquid chromatography with diode-array detection (HPLC-DAD)

A HPLC-DAD method for the determination of cysteamine supplementation in commercial animal feeds was developed. Samples were extracted with a mixture of 0.5 % hydrochloric acid – acetonitrile (90:10, v/v), matrix interferences were removed with a C18 cartridge, cysteamine was derivatized using 5,5'-dithiobis-(2-nitrobenzoic) acid (DTNB) as Ellman's reagent targeting to the thiol group in the molecule. Quantification of cysteamine was performed on a c18 column with DAD at 323 nm. The developed method had LOD of 1.1 mg/l, good linearity of the calibration curve (R2 ≥ 0.9998), high recoveries (> 92 %), and high reproducibility (RSD < 2.0%).