Additively manufactured electrodes using custom-made recycled PLA, carbon black and graphite ready-to-use to determine ketamine in spiked beverage samples

The use of drugs of abuse is a significant global issue. Each year, around half a million deaths are attributed to drug overdoses [1]. Additionally, many drugs are used to facilitate sexual assaults, commonly referred to as “date rape drugs.” Accurately quantifying the prevalence of these drugs is challenging [2]. The European Monitoring Centre for Drugs and Drug Addiction reports that 75% of rape victims were drugged with illicit substances, alcohol, or a combination of both [3]. In this work, we propose the construction of AMEs using FFF technology to detect ketamine (KET) in spiked beverage samples (vodka, red wine, beer, white wine, and drinking water). A conductive filament made of recycled PLA containing carbon black, graphite, and castor oil was used to produce the working electrodes. The Gpt-CB-rPLA electrode exhibited superior electrochemical performance compared to the commercial filament, without any pre-treatment step. For the [Fe(CN₆)]³⁻/⁴⁻ probe, the peak-to-peak separation was 130 ± 3 mV for the laboratory-fabricated electrode and 759 ± 3 mV for the commercial one. The same was observed for the outer-sphere probe ([Ru(NH₃)₆]³⁺/²⁺), where the separation was 67±1 mV and 75±1 mV, respectively. Moreover, lower charge transfer resistance (Rct) was observed for the recycled material filament (1.04 kΩ ± 0.05) compared to the commercial one (9.62 kΩ ± 0.03). The Gpt-CB-rPLA electrode also demonstrated excellent sensitivity, reaching 0.024 ± 0.001 μA μmol L⁻¹, with a detection limit (LOD) of 0.7 μmol L⁻¹ and a linear response range of 10 to 250 μmol L⁻¹. The standard addition method resulted in recovery rates ranging from 82% to 115%.