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 (R(2) = 0.9985, n = 8) with a detection limit (3s) of 1.43 × 10(-3) mg/L for retinol and 2.15 mg/L (R(2) = 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.