Detection of haloacetic acids at conductive electroactive polymer-modified microelectrodes

Conducting polymer modified microelectrodes have been developed as sensors for haloacetic acids. Both 10 and 50 mu m microelectrodes were studied, the 50 Irm microelectrodes proving superior. The polymer electrodes tested were polypyrrole/chloride (PPy/Cl), polypyrrole/dodecylsulfate (PPy/DS), polypyrrole/sulfobenzoic acid (PPy/SBA) and polypyrrole/p-toluene sulfonate (PPy/PTS). Excellent linear calibration graphs were obtained (99.9% confidence) for monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic acid (DBAA). The best detection limits for MCAA (1 ng ml(-1)), DCAA (10 ng ml(-1)), TCAA (0.1 mu g ml(-1)) and DBAA (0.1 mu g ml(-1)) obtained at the PPy/SBA electrode are better than those obtained by conductivity detection. The mechanism of detection for haloacetic acids has been elucidated by simultaneous cyclic voltammetry and electrochemical piezoelectric quartz crystal studies which show that the electroactivity of the polymer modified electrode is associated with the incorporation and expulsion of the anions of these acids.