A novel HPLC-UV/nano-TiO2-chemiluminescence system for the determination of selenocystine and selenomethionine

Active oxygen species from the photocatalytic reaction in aqueous solution react with luminol to emit strong chemiluminescence (CL), and this can be inhibited by the UV decomposed-products of selenocystine (SeCys) or selenomethionine (SeMet). Based on this phenomenon, a novel hyphenated technique, HPLC-UV/nano-TiO2-CL, was established for the determination of SeCys and SeMet. The effects of pH, the UV irradiation time, the TiO2 coated on the inner surface of the reaction tubing, and the Co2+ catalyst concentration on the CL intensity and/or chromatographic resolution were systematically investigated. Under these optimized conditions, the inhibited CL intensity has a good linear relationship with the concentration of SeCys in the range of 0.04–10.6 μg mL−1 or SeMet in the range of 0.05–12.4 μg mL−1, with a limit of detection (S/N = 3) of 6.4 μg L−1 for SeCys or 12 μg L−1 for SeMet. As an example, the method was preliminarily applied to the determination of the selenoamino acids in garlic and rabbit serum, with a recovery of 88–104%.