Application of a tubular copper electrode as a potentiometric detector in the determination of amino acids by high performance liquid chromatography.

A copper tubular electrode (CTE) has been used as a potentiometric detector in the determination of amino acids by reversed-phase high-performance liquid chromatography. The reference electrode was an electrically grounded tubular platinum electrode inserted in the flow stream. Comparison with a variable-wavelength UV absorbance detector showed that the CTE gave comparable response time and sensitivity, but was much more selective, showing response only to copper-binding molecules. The CTE has been applied to the analysis of urine and an intravenous amino acid preparation; no sample pre-treatment was required, other than filtration. Microgram quantities of amino acids were readily detected by using the CTE.