Multi-analyte sensing: a chemometrics approach to understanding the merits of electrode arrays versus single electrodes

A peptide-modified electrode array with a different peptide on each electrode is compared with a single electrode modified with many peptides for the voltammetric measurement of concentrations of Cu2+, Cd2+ and Pb2+ in solution. The single gold electrode was modified simultaneously with peptides Gly-Gly-His, glutathione and angiotensin I each coupled to thioctic acid, and thioctic acid itself, and the calibration of mixtures of ions was compared with previously published data from an array of four sensors each with an individual modification. Calibration at the multi-peptide single-electrode sensor was by two-way partial least squares (voltammetric current measured with variables ‘sample’ × ‘potential’) and for the electrode array by three-way NPLS1 (‘sample’ × ‘potential’ × ‘electrode’). The advantage of designing experiments to yield multi-way data is demonstrated and discussed.