AbstractVolatile fatty acids in aqueous media were esterfied in situ with phenyldiazomethane (PDM). Complete esterification was achieved in 3 h at 40°C under continuous stirring of an ether/water system. The process involved immediate transfer of benzyl esters into the organic phase. The separation of benzyl esters mixtures was carried out in glass capillary GC columns. The retention data and FID molar responses were determined for C1 to C6 acid benzyl esters, including 2‐methylpropionic, 3‐methylbutyric, 2‐methylvaleric, and 2‐ethylbutyric acid. An unusual relationship was observed between benzyl ester relative molar responses and carbon ato