Detection of amino acids at conducting electroactive polymer modified electrodes using flow injection analysis .2. Use of microelectrodes

Conducting electroactive polymer modified microelectrodes (10 mu m 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 (SEA(-)), 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 7.5x10(-6) to 1x10(-4)M. The sensitivities were 1.510 and 1.475 nC mol l(-1) for aspartic acid and glutamic acid respectively. The limit of detection was 3x10(-6) M (0.4 mu g ml(-1)) for both aspartic acid and glutamic acid.