Immunoanalytical techniques have found widespread use due to the characteristics of specificity and wide applicability for many analytes, from large polymer antigens, to simple haptens, and even single atoms. Electrochemical sensors offer benefits of technical simplicity, speed and convenience via direct transduction to electronic equipment. Together, these two systems offer the possibility of a convenient, ubiquitous assay technique with high selectivity. However, they are still not widely used, mainly due to the complexity of the associated immunoassay methodologies. A separation-free immunoanalytical technique is described here, which has allowed for the analysis of atrazine in real time and in both quasi-equilibrium and stirred batch configurations. It illustrated that determinations as low as 0.13 μM (28 ppb) could be made using equilibrium incubation with an analytical range of 0.1-10 μM. Measurements could be made between 1 and 10 mM within several minutes using a real-time, stirred batch method. This system offers the potential for fast, simple, cost-effective biosensors for the analysis of many substances of environmental, biomedical and pharmaceutical concern. (C) 2001 Elsevier Science B.V.