Effects of 105 traditional Chinese medicines on the detection of β-agonists in medicine extracts and swine urine based on colloidal gold immunochromatographic assay

Abstract

Colloidal gold immunochromatographic assay (CGIA) is commonly used for the on-site detection of β-agonists that are sometimes used illegally as feed additives in swine diets. However, few studies have evaluated the causes of false-positive results that sometimes occur when applying CGIA in agricultural settings. In this study, we investigated if this false-positive phenomenon is related to the addition of certain traditional Chinese medicines (TCMs) to swine feed. We established and verified an extraction method for TCMs, and then applied CGIA to detect β-agonists in the extracts of 105 TCMs and in the urine of swine dosed with TCMs, respectively. Liquid chromatography-tandem mass spectrometry was used to validate the results of the urine samples tested positive for β-agonists using CGIA. The results were also verified using TCMs and colloidal gold test strips produced by different manufacturers. The extracts of Citri Reticulatae Pericarpium Viride, Citri Reticulatae Pericarpium, Magnoliae Officinalis Cortex, Chaenomelis Fructus, and Rhodiolae Crenulatae Radix Et Rhizoma were tested positive for β-agonists. Meanwhile, the addition of Citri Reticulatae Pericarpium Viride and Citri Reticulatae Pericarpium to swine feed resulted in false-positive results for β-agonists in swine urine. The results provide a new way to explain false-positive CGIA results and provide valuable information for livestock feeding programs.