# Matrix effect of four Chinese medicinal herbs on colloidal gold immunoassay for organophosphorus pesticides

## TL;DR

This study examines how four Chinese medicinal herbs affect the accuracy of colloidal gold test strips used to detect organophosphorus pesticides.

## Contribution

A new extraction method is proposed to reduce matrix effects and improve detection accuracy in immunoassays for pesticide residues.

## Key findings

- The extraction method eliminated matrix interference for chlorpyrifos, triazophos, and isocarbophos.
- Sensitivity of the test strips increased by 8.3, 1.7, and 1 times, respectively, compared to standard methods.
- Natural products and secondary metabolites in herbs are hypothesized to cause matrix effects in immunoassays.

## Abstract

The matrix effect (ME) presents a serious problem for the immunoassay of pesticide residues, considerably limiting its practical application in Chinese medicinal herbs and other food products. The objective of this study was to achieve reduced matrix effect and improved detection accuracy of colloidal gold test strips. For that reason, four types of Chinese medicinal herbs (Ophiopogon japonicus, Bulbus Fritillaria, Polygonatum sibiricum, and Folium Artemisiae Argyi) were used as samples to investigate the effect of the Chinese medicinal herb matrix on the gold immunochromatographic assay (GICA) for analyzing three organophosphorus pesticide (chlorpyrifos, triazophos, and isocarbophos) residues. In the quantitative analyses of chlorpyrifos, triazophos and isoprocarbophos, the extraction method completely eliminated the matrix interference, and the sensitivities of GICA were increased by about 8.3, 1.7 and 1 times, respectively, compared with those of the standard operating instructions for test strips. The mechanism of the matrix of Chinese herbal medicines on the ME of colloidal gold test strips was preliminarily explored. It is reasonable to hypothesize that natural products and secondary metabolites have a significant effect on GICA, leading to ME.