Schematic of sequential injection/electrochemical immunoassay for quantification of 3,5,6-trichloro-2-pyridinol (TCP). The computer controlled sequential-injection analysis system (MicroSIA, FIAlab Instruments Inc., WA) includes six-port selection valve for delivering sample and reagents, a thin-layer cross-flow cell (MF-1095, Bioanalytical system Inc., West Lafayette, IN) that contains a glassy carbon electrode, a Ag/AgCl reference electrode and electrochemical analyzer voltammetric detection of electroactive species (Model CHI 660, CH Instruments Inc., TX). Figure adapted from Liu et al. (2005) with permission.