An amperometric detector for use with small-bore liquid chromatographic columns.

A miniaturized electrochemical flow cell for amperometric detection in liquid chromatography has been designed to meet the requirement of low volumetric dispersion when using small-bore columns. The volume of the thin-layer cell is in the range 10-50 nl, depending on the spacer dimensions, with the electrode area being about 1 mm2. The cell is constructed from glass and designed in such a way that the working electrode can be mounted without alterations to its surface state. The flow-rate dependence, contribution to peak dispersion and linear dynamic range were investigated. After separation on a 250 X 1 mm I.D. column, a detection limit for dopamine of about 0.15 pg was achieved with a linear dynamic range of 10(6). The variance of the extra-column dispersion was determined to be less than 0.3 microliter2, including injector and connecting capillaries. The applicability of the detector is illustrated with the detection of dopamine and its major metabolites, dihydroxyphenylacetic acid and homovanillic acid, and of Met- and Leu-enkephalin in samples of biological origin.