Electrochemiluminescence quantification of amine functionalized drugs at Ru(bpy)₃²⁺/poly(4-amino-diphenylamine) sensor incorporated with AuNPs: Potential analysis of ephedrine

An electrochemiluminescence (ECL) sensor based on a sandwich gold nanoparticles (AuNPs) linkage species amid luminescence molecules, [Ru(bpy)3]²⁺, doped at a pre-alkaline poly(4-aminodiphenylamine), t-Padpa, film has been employed for the quantification of some tertiary amines including buspirone (BUS), triprolidine (TPL), diphenhydramine (DPH) and chlorpheniramine (CPM). The proposed sensor (Ru.AuNPs.Ru.t-Padpa/GCE) showed high sensitivity and good stability with limit of detection (LOD) low enough for successful application and determination of above drugs in their pharmaceutical formulation. The relationship between the observed ECL intensity and the structural attribute of these drugs was justified by the type of attached nitrogen functionalities, the presence of electron donating or electron withdrawing groups and the extent of anodic potential. The potential analysis of ephedrine (EPH), a secondary amine, proceeded by in-situ derivatization reaction with formaldehyde to produce a strongly ECL susceptible aminol intermediate. Variation of EPH concentration at constant amount of formaldehyde significantly enhances ECL signals and drops the LOD of EPH into 1.2 ng/mL. Real sample analysis of EPH was satisfactorily recovered regardless of drug matrixes and presence of interference species. The protocol of sensor construction along with the reductive addition reaction confirms that the present ECL approach meets the highest demand required for EPH analysis.