Flow injection methods for the determination of retinol and α‐tocopherol using lucigenin‐enhanced chemiluminescence

Flow injection (FI) methods are reported to determine retinol and α‐tocopherol based on its enhancement affect of lucigenin chemiluminescence (CL) in alkaline medium. Surfactants including Brij‐35, Triton X‐100, cetyltrimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate have been reported for the first time to enhance lucigenin CL intensity in the presence of retinol and α‐tocopherol. With Brij‐35, the CL intensity was enhanced by 67% for retinol and 58% for α‐tocopherol. CTAB was found to enhance the CL intensity by 16% for retinol whereas for α‐tocopherol, the CL intensity was quenched up to 95%. Retinol could be determined specifically in the presence of α‐tocopherol using CTAB. The calibration graphs were found to be linear up to 1.43 mg/L (R² = 0.9985, n = 8) with a detection limit (3s) of 1.43 × 10^?3 mg/L for retinol and 2.15 mg/L (R² = 0.9989; n = 8) with a detection limit (3s) of 4.31 × 10^?4 mg/L for α‐tocopherol. An injection throughput of 120/h, and relative standard deviations of 0.9–2.8% (n = 4) were achieved in the concentration range studied. The influence of common ions, excipients in pharmaceutical formulations and related organic compounds on the determination of retinol and α‐tocopherol individually was studied. The proposed methods were applied to determine retinol and α‐tocopherol in pharmaceutical formulations and human blood serum. The results did not differ significantly from the CL method and HPLC reference method at 95% confidence level. Copyright © 2010 John Wiley & Sons, Ltd.