Disposable amperometric immunosensor for the detection of polycyclic aromatic hydrocarbons (PAHs) using screen-printed electrodes

An amperometric immunosensor for polycyclic aromatic hydrocarbons (PAHs) was developed. The immunosensor was based on disposable screen-printed carbon electrodes. The coating antigen used was phenanthrene-9-carboxaldehyde coupled to bovine serum albumin (BSA) via adipic acid dihydrazide. Antibodies were monoclonal mouse anti-phenanthrene. The enzyme alkaline phosphatase (AP) was used in combination with the substrate p-aminophenyl phosphate (pAPP) for detection at +300 mV (vs. Ag/AgCl). Various assay types were compared. Good results were achieved with an indirect co-exposure competition assay with a LOD of 0.8 ng/ml (800 ppt) and an IC50 of 7.1 ng/ml (7.1 ppb) for phenanthrene. An indirect competition assay could detect phenanthrene with a LOD of 2 ng/ml (IC50: 15 ng/ml) and an indirect displacement assay with a LOD of 2 ng/ml (IC50: 11 ng/ml) at a 5 mul surface coating of 8.8 mug/ml phenanthrene-BSA conjugate. A coating concentration of 2.2 mug/ml allowed detection with a LOD of 0.25 ng/ml (250 ppt) with the indirect competition assay. The influence of the coating concentration on the sensor performance was investigated. Cross-reactivities were tested for 16 important PAHs. Anthracene and chrysene showed strong cross-reactivity, whereas benzo[g,h,i]perylene and dibenzo[a,h]anthracene showed no cross-reactivity. (C) 2002 Elsevier Science B.V. All rights reserved.