Zwitterionic oligomers of 3-aminobenzoic acid on screen-printed electrodes: structure, properties and forensic...

The popularity and rapid spread of new psychoactive substances is why there is an urgent need for their fast monitoring in saliva in the field with electrodes modified with a selective receptor. Oligomers of electrochemically oxidized 3-aminobenzoic acid that are deposited on the surface of a graphite screen-printed electrode (o-3ABA/G/SPE) is proposed as a selector for the analyte of forensic interest. The oligomeric structure and existence of the zwitterionic form of o-3ABA on the G/SPE surface was confirmed using scanning electron microscopy, Raman spectroscopy and cyclic voltammetry techniques. The equilibrium adsorption constants between o-3ABA and 2-aminoindane (primary amine: K_ads(2-AI) = 5.31 × 10⁴) and selected synthetic cathinones (secondary amine: K_ads(butylone) = 6.12 × 10⁵, tertiary amines: K_ads(MDPV) = 3.41 × 10⁴ and K_ads(naphyrone) = 1.01 × 10⁴) were estimated using the electrochemical impedance spectroscopy (EIS) technique. The EIS technique was applied for determining a 1.0 μM concentration of 2-AI (RSD 3.5-4.0%) and butylone (RSD 4.9-6.4%) in the model and oral fluid samples.