Collaborative Study Comparing Gas-Liquid Chromatographic and Chemical Methods for Quantitatively Determining Vitamin E Content of Pharmaceutical Products

Abstract

Abstract A collaborative study was conducted to compare the USP XVII (Emmerie-Engel) method and three GLC methods for quantitatively determining a-tocopherol, a-tocopheryl acetate, and a-tocopheryl succinate in pharmaceutical products. Nine collaborating laboratories analyzed seven pharmaceuticals encompassing tablets, capsules, and liquids. The mean coefficients of variation were: USP method, 28.6%; GLC method A, 10.2%; GLC method B, 10.8%; GLC method C, 18.0%. GLC method A was the method of choice of those evaluated. The vitamin E analogs are extracted with n-hexane from ground tablets and capsules; liquid preparations are diluted with n-hexane or injected directly onto the GLC column. The compounds are chromatographed on an 8′ × 4 mm id glass column paeked with 5% SE-30 on 100-120 mesh silanized Gas Chrom P, operated between 270-285°C, and the carrier gas flow rate adjusted so that ∝-tocopheryl acetate appears within 23-27 min. Acetic anhydride-pyridine reaction is utilized to determine whether ∝-tocopherol or ∝-tocopheryl succinate is present in a sample, since these two analogs have similar retention times. It is recommended that GLC method A be adopted as official first action.