A highly sensitive and specific indirect competitiveenzyme-linked immunosorbent assay (ELISA) for thedetermination of diclofenac in water samples was developed.With pure water, the limit of detection (LOD, S/N ) 3)and IC50 were found to be 6 ng/L and 60 ng/L, respectively.The analytical working range was about 20-400 ng/L.Highest cross-reactivity (CR) of 26 tested pharmaceuticals,metabolites, and pesticides was found for 5-hydroxydiclofenac(100%). Other estimated values were well below4% and, therefore, are negligible. The assay was appliedfor the determination of diclofenac in tap and surface watersamples as well as wastewater collected at 20 sewagetreatment plants (STPs) in Austria and Germany. Humicsubstances were identified as main interference in surfacewater. Wastewater samples which were only submittedto filtration and dilution yielded about 25% higher diclofenacconcentrations using the ELISA compared to GC-MS.However, the ELISA turned out to be a simple, inexpensive,and accurate method for the determination of diclofenacboth in influent and effluent wastewater after rather simplesample preparation, i.e., filtration, acidification, andreadjustment to neutral pH-value, and at least 10-folddilution with pure water.

The high sensitive dynamic reaction cell inductively coupled plasma mass spectrometry (DRC ICP-MS)-based immunoassayusing ferrocene (Fc) tethered hydroxysuccinimide ester as label for the determination of 2,4-dichlorophenoxyacetic acid(2,4-D) was presented. Ferrocene tethered hydroxysuccinimide ester was directly or via horse radish peroxidase (HRP) as abridge coupled to monoclonal antibody (mAb) of 2,4-D. Competitive immunoreactions were completed in microtiter plateand the signal of 56Fe in the bound ferrocene labeled conjugate was detected by DRC ICP-MS. The potentially interfering40Ar16O+ at the iron mass m/z 56 was reduced in intensity significantly by using NH3 as the reaction gas. The optimizationprocess of the immunoassay was greatly simplified in the aid of enzyme linked immunosorbent assay (ELISA) procedure. The2,4-D was determined in the dynamic range of 0.1–1000 ng/ml and the detection limits of the assays using the two ferrocenelabeled conjugates were found to be 0.044 and 0.055 ng/ml, respectively. The relative standard deviation for six measurementswere within 5.5–15.3%.

A sequential injection instrument (ALITEA, USA) with a photometric and fluorometric detection unit S2000 (Ocean Optics) was employed for the development of flow injection immunoanalysis (FIIA). The monoclonal antibodies against atrazine, simazine and 2,4-D were immobilized on aminopropyl glass particles by means of avidin/biotin system and packed in plexiglass column of 18ml volume. Assay characteristics for individual antibody-reactors and regeneration effectivities for acid and alkaline solutions are described. An attempt to prepare a functional mixed antibody-reactor has not achieved success since regeneration conditions found for individual reactors were not compatible with one performance protocol.

To extend the application of a multichannel electrochemical detector (MED) for immunoassay, a MED system consisting of 8 sets of Pt electrodes in an arrangement fitted with the dimensions of a row of microtiter wells in a microtiter plate and a microcomputer-assisted 16-channel potentiostat was constructed. With this developed MED system, electroactive enzymatic products produced in eight microtiter wells can be analyzed simultaneously with a developed amperometric procedure. To demonstrate the applicability of the MED system for immunoassay, an immunosystem containing rabbit-IgG and alkaline phosphatase-conjugated goat anti rabbit-IgG was studied. From the dynamic range of 10-1000 ng/mL (0.064-6.4pM) and the detection limit of 1.0 ng/mL (6.4pM) obtained, the developed MED shows a tremendous improvement in sensitivity, detection limit, and efficiency compared with that obtained from conventional electrochemical immunoassay.

lic acid spacers at para-position were derived from coplanar 3,3,4,4-tetrachlorobiphenyl and 3,3_,4,4_,5-pentachlorobiphenyl (IUPAC No. 77 (PCB 77) and 126 (PCB 126), respectively). It appeared from the results that the length of the spacer did not affect significantly the sensitivity of the assays established. The direct ELISAs using the antibodies in combination with various hapten–peroxidase tracers showed IC50-values for polychlorinated biphenyl (PCB) 77 and 126 of 1.3–19.2μg l−1. The ELISAs were tested for their cross-reactivity profiles using 20 selected congeners. The assays were highly specific for non-ortho-substituted (coplanar) congeners and did not recognize the more abundant but less toxic non-coplanar PCBcongeners or organochlorine compounds. The superior assaywas found for the antibody againstPCB126-(CH2)3-hapten mimic–bovine serum albumin (BSA) in combination with PCB 77-CH2-hapten mimic-peroxidase tracer. The IC50-values for the assay to PCB 77 and 126 were 2.0 and 5.2μg l−1, respectively; the highest cross-reactivity values (PCB 126=100%) achieved for non-coplanar structures and metabolites were only 1.3 and 1.0% for 2,3,3,4,4,5,5 heptachlorobiphenyl (PCB 189) and PCB 77 ether, respectively. In order to interpret measured data in terms of analytical or toxicological equivalents, a reliable relationship between assay responses and the coplanar congener content of Aroclor-contaminated samples should be verified and validated.