DETECTION OF HALOACETIC ACIDS AT CONDUCTIVE ELECTROACTIVE POLYMER-MODIFIED MICROELECTRODES

Conducting polymer modified microelectrodes have been developed as sen sors for haloacetic acids. Both 10 and 50 mu m microelectrodes were st udied, the 50 Irm microelectrodes proving superior. The polymer electr odes tested were polypyrrole/chloride (PPy/Cl), polypyrrole/dodecylsul fate (PPy/DS), polypyrrole/sulfobenzoic acid (PPy/SBA) and polypyrrole /p-toluene sulfonate (PPy/PTS). Excellent linear calibration graphs we re obtained (99.9% confidence) for monochloroacetic acid (MCAA), dichl oroacetic acid (DCAA), trichloroacetic acid (TCAA) and dibromoacetic a cid (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)) obtaine d at the PPy/SBA electrode are better than those obtained by conductiv ity detection. The mechanism of detection for haloacetic acids has bee n elucidated by simultaneous cyclic voltammetry and electrochemical pi ezoelectric quartz crystal studies which show that the electroactivity of the polymer modified electrode is associated with the incorporatio n and expulsion of the anions of these acids.