2.4- dichlorophenoxyacetic acid immunoassay

J. Horacek and P. Skladal, Improved direct piezoelectric biosensors operating in liquid solution for the competitive label-free immunoassay of 2,4-dichlorophenoxyacetic acid. Anal. Chim. Acta 347, 43-50 (1997). 

The detection limit was 0.1 pM 2,4-D, comparable to that of the radioassay, and the response range was 0.1-50 pM in buffer. Cross-reactivity of the polymer towards 2,4-dichlorophenoxyacetic acid methyl ester (2,4-D-OMe) was lower than that reported for immunoassays. 

Chlorophenoxy acid herbicides are also widely used to control broadleaf weeds and grass plants. Several immunoassays have been reported for 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T).246 247 Several immunosensors have been described using a transducing principle similar to the RIANA system already described in this chapter. Thus, Meusel et al.248 reported the use of monoclonal antibodies in a sensor chip to analyze river and lake water samples, obtaining detection limits of 0.1 ig L 1. Moreover, monoclonal antibodies, produced by Cuong et al.,249 were used in a dipstick immunoassay format to analyze pond water samples. When applied to the 2,4-D compound, this semiquantitative method yielded for an IC50 of 6 ug I. and an LOD of 0.5 pg L-1. 

Cuong, N.V., T.T. Bachmann, and R.D. Schmid. 1999. Development of a dipstick immunoassay for quantitative determination of 2,4-dichlorophenoxyacetic acid in water, fruit and urine samples. Fresenius J. Anal. Chem. 364 584-589. 

Hedcer, J. Two enzyme immunoassays to screen for 2,4-dichlorophenoxyacetic acid in water. J. Assoc. Off. Anal. Chem., 70 874-8. 1987. 

This is then concentrated in the polyanionic Nafion film coating the electrode and quantified by cyclic voltammetry as shown in Fig. 8.19. The feasibility of this immunoassay has been demonstrated for a herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D) with a detection limit of 0.01 pg [89]. 

Deng AP, Yang H (2007) A multichannel electrochemical detector coupled with an ELISA microtiter plate for the immunoassay of 2,4-dichlorophenoxyacetic acid. Sensor Actuator B Chem 124 202-208... 

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