Influence of extra‐column effects in capillary gas chromatography

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Abstract
The contribution of extra‐column effects to the height equivalent to a theoretical plate (HETP) in capillary gas chromatography is calculated. Four extra terms are added to the Golay‐Giddings equation and evaluated in order to verify their significance. The paradox of negative A terms is resolved by curve fitting of experimental values to the theoretical function of HETP, including the extra‐column effects. The importance of the A term and the diffusion process for an injection in split mode were determined to be negligible compared to the other terms in the HETP equation. On the other hand, extra‐column contributions, proportional to the square of the gas velocity, are of significant importance. This contribution is inversely proportional to the column length.