Abstract
The direct and indirect competition time-resolved fluorescence immunoassays (dc-TRFIA, ic-TRFIA) were established by combining the autofluorescence properties of lanthanide europium (Eu) with the monoclonal antibody of oxyfluorfen. The purified Eu antibody was optimized and the conditions such as the working concentration of the Eu antibody, monoclonal antibody, and working buffer were optimized. In the optimal condition, the IC50 of dc-TRFIA was 10.27 ng/mL, the lowest detection limit IC10 was 0.071 ng/mL, the detection range (IC10-IC90) was 0.071–1074.3 ng/mL, and the detection range (IC10-IC90) and IC50 of ic-TRFIA were 0.024–504.6 and 2.76 ng/mL, respectively. The comparison showed that the sensitivity and detection limit of ic-TRFIA were superior to dc-TRFIA. The cross reaction (CR) tests showed that the CR with other oxyfluorfen structure analogs was <0.02%, except that there was a certain CR with the benzofluorfen (CR = 11.58) and the bifenox (CR = 8.23%). The average recoveries of ic-TRFIA were 74.6–108.3%, and the RSDs were between 2.1 and 10.9%, in the addition recovery test with five substrates. The results of the correlation test with the real samples of GC-ECD showed that they were highly correlated (y = 0.975x – 0.4446, R2 = 0.9901), which proved that the TRFIA method established in this study had high reliability and accuracy and could be used in environment and agricultural products for rapid detection of oxyfluorfen residues.
Highlights
Oxyfluorfen [2-chloro-α, α, α-trifluoro-p-tolyl-(3-ethoxy-4-nitro-phenyl)] is a kind of fluorinated diphenyl ether herbicide that developed by the Rohm and Hass (Sheng et al, 2020)
The solutions were combined according to the number of collection tubes, and their labels were used for subsequent timeresolved fluorescence immunoassay (TRFIA) method research
The TRFIA method established in this study used a time-resolved detection mode to minimize the interference of background fluorescence and improve the accuracy of the detection results
Summary
Oxyfluorfen [2-chloro-α, α, α-trifluoro-p-tolyl-(3-ethoxy-4-nitro-phenyl)] is a kind of fluorinated diphenyl ether herbicide that developed by the Rohm and Hass (Sheng et al, 2020). Oxyfluorfen cannot be metabolized by plants; it can only be slowly assimilated by microorganisms, and this issue has gradually attracted people’s attention. Such as the United States Food and Drug Administration (FDA) and Health Canada have revised the maximum residue limit (MRL) of oxyfluorfen twice in 3 years (2014 and 2017) (Sheng et al, 2018). It is necessary to establish rapid, highly sensitive, economical, and friendly methods for the detection of residual oxyfluorfen. The unique fluorescence characteristics of lanthanides make TRFIA a new immunoassay method with high sensitivity, no interference from background fluorescence, broad spectrum, large Stokes shift, dissociation enhancement, and no radioactivity (Shi et al, 2015). TRFIA, as a new label detection technology that only emerged in the 1990s, has been widely used in medical, environmental, and agricultural pollutant detection methods, and it is bound to bring new vitality to label immunoassay technology
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