Detection of amino acids at conducting electroactive polymer modified electrodes using flow injection analysis. Part II. Use of microelectrodes

Conducting electroactive polymer modified microelectrodes (10 μm cross sectional diameter) have been applied to detect amino acids in a flow injection system. Conducting polymers were deposited on the electrode surface incorporating a range of counterions (chlorine (Cl−), sodium dodecyl sulphate (DS−), 3-sulfobenzoic acid sodium salt (SBA−), 4-hydroxybenzene-sulfonic acid sodium salt (HBSA−), p-toluenesulfonic acid sodium salt (PTS−) and (1S)-(+)-10-camphorsulfonic acid (CSA−). The electrodes were responsive to four amino acids investigated, aspartic acid, serine, alanine and arginine with maximum response obtained for aspartic acid. Linearity of calibration was demonstrated by the polypyrrole/3-sulfobenzoic acid sodium salt (PPy/SBA) sensor for aspartic acid and glutamic acid over the range 7.5 × 10−6 to 1 × 10−4 M. The sensitivities were 1.510 and 1.475 nC mol 1−1 for aspartic acid and glutamic acid respectively. The limit of detection was 3 × 10−6 M (0.4 μg ml−1) for both aspartic acid and glutamic acid.