Colorimetric Determination of Carvone in Volatile Oils in the Presence of Menthone and Pulegone

Abstract Carvone, menthone, and pulegone in volatile oils are determined by measuring at 370 nm the color obtained by their reaction with 3,5-dinitrobenzoic acid (DNBA) or m-dinitrobenzene (DNB). The DNBA method is sensitive to 50—1500 μg carvone or pulegone/10 mL and to 500-1500 μg menthone/10 mL. The DNB method is as sensitive to carvone and menthone as is the DNBA method, but it is less sensitive to pulegone (300—1500 μg/10 mL). Either carvone or pulegone in the presence of menthone can be determined by using the DNBA method at concentrations less than 500 μg menthone/10 mL. Carvone can also be estimated by the DNB method without pulegone and menthone interference when these constituents are present at levels less than 300 and 500 μg/10 mL, respectively. Other ketonic constituents, piperitone, methyl heptenone, and ionone, did not respond to the color reaction except at concentrations above 750 μg/10 mL. The method was successfully used for the estimation of carvone in oils of Mentha viridis, M. crispa, caraway, and dill.