Ag-decorated sulfur-rich covalent organic framework for SERS fingerprinting of β2-adrenergic agonists olodaterol, indacaterol, and formoterol.
Li Min M, Yang Fang F, Huang Qingyu Q, Luo Xiaojun X
Olodaterol, indacaterol, and formoterol are the most frequently abused β2-agonists. The World Anti-Doping Agency (WADA) has imposed a threshold limit of 40 ng/mL for formoterol in urine and a total ban on olodaterol and indacaterol. Therefore, it is urgent to develop sensitive analytical methods for the identification and quantification of the three compounds. Herein, for the first time, we fabricated a sulfur rich covalent organic framework supported silver-nanoparticle (Ag-SCOF) substrate for surface enhanced Raman spectroscopy (SERS). Benefiting from the strong Ag-S covalent bonds, silver nanoparticles can be firmly anchored on the SCOF matrix to effectively suppress nanoparticle aggregation and improve substrate stability. Target β2-agonists can be enriched into electromagnetic hot spots via Ag-N interactions, thereby greatly amplifying Raman signals. The analytical enhancement factor of this substrate reaches 3.89 × 105. The limits of detection (LODs) for olodaterol, indacaterol, and formoterol reach 8.61 × 10⁻8, 8.03 × 10⁻8, and 9.63 × 10⁻8 g·mL⁻1, respectively. This Ag-SCOF SERS platform achieves rapid (within 3 min), fingerprint-based simultaneous detection, overcoming the drawbacks of conventional methods such as high cost, long assay time and low specificity. The proposed method fully meets the detection requirements of WADA regulations and food safety monitoring, and has great potential for on-site analysis of real samples.