Pretreatment-free detection of diazepam in beverages based on a thermometric biosensor

•A FIA-TELISA method for the pretreatment-free detection of diazepam (DZP) in real samples was constructed based on a direct competition.•This method had good specificity and repeatability, and possessed high consistence with HPLC method.•Our studies provided a promising assay model which was capable of continuously monitoring analytes without elaborate extraction procedures to correct the matrix effect of the beverages.