Colorimetric quantification of α-tocopherol (vitamin E) in pure form and different comestible samples by using newly synthesized tetrazolium salts

A quick, susceptible, and viable spectrophotometric procedure for the assay of α-tocopherol by newly synthesized tetrazolium reagents 2-phenyl-3-(2-thiazolyl)-5-(4-methoxyphenyl)tetrazolium bromide (PTMPT) and 2-phenyl-3-(2-thiazolyl)-5-(4-nitrophenyl)tetrazolium bromide (PTNPT) is reported. The reduction behavior of α-tocopherol is used to quantify it in pure form and different edibles. Colorless tetrazolium salt-reduced in the pink-colored formazan by α-tocopherol gives absorption maxima at 526 nm. The reduction process occurred in the basic medium, so the pH of the reaction medium was maintained in the range 8–9. Beer’s law was obeyed in the concentration range of 0.2–15.0 μg/mL with PTMPT and 0.1–0.4 μg/mL with PTNPT. The molar absorption coefficient is 4.21 × 103 L mol−1cm−1 and 6.4 × 104 L mol−1cm−1 with PTMPT and PTNPT, respectively. Limit of detection is 0.14 μg/mL and 0.03 μg/mL, and limit of quantification is 0.42 μg/mL and 0.08 μg/mL for α-tocopherol with PTMPT and PTNPT, respectively. As the proposed method is easy and user-friendly, distinct edibles are quantified by using the proposed method, and the results show good agreement with the other existing methods. The samples were saponified first to convert α-tocopheryl acetate in its active form, i.e., α-tocopherol. Saponification had done at temperature 70 °C for 2 h on heating mental. The values of the correlation coefficient (R2) are 0.955 and 0.998 with the relative standard deviation of 0.8% and 4.6% with PTMPT and PTNPT, respectively. The proposed method is effectively used for the assay of α-tocopherol in different pharmaceuticals, fruits, cereals, nuts, and milk samples.