Acetaminophen

The chemicals BaCl₂.2H₂O, CoCl₂.2H₂O, and CuCl₂.6H₂O (reagent grade RG) were purchased from Merck, FeCl₃ was bought from Sigma Aldrich, >98% purity citric acid and C₆H₈O₇ from Merck, RG grade propylene glycol (C₃H₈O₂) and glycerin (C₃H₈O₃) were from Merck. NH₄OH (RG grade) and acetaminophen (Analytical grade AG) were used as received from Merck. The AG-grade PBS solution (supporting electrolyte) (0.1-M KH₂PO₄) was purchased from Merck, and the pH was adjusted using 0.1-M KOH (AG grade, Merck) and H₃PO₄ from Sigma Aldrich at a ratio of 1:1. The solutions were prepared using distilled water. The citrate sol gel method was utilized for the synthesis of the transition-metal-substituted barium ferrite nanomaterials, which were characterized using XRD, SEM, Fourier-transform infrared, and Raman analysis techniques [20 (link)].

All chemicals used in this study were of analytical grade and were used as received from the manufacturer without further purification. All solutions used were prepared with ultrapure water (18.2 MΩ, Millipore Simplicity). Cocaine, methamphetamine, MDMA, MMC, PVP where purchased from Cayman Chemicals, while, acetaminophen, benzocaine, K₂HPO₄, KH₂PO₄, KCl, H₂PtCl₆, HCl, HAuCl₄, H₂SO₄, [Fe(CN)₆]^4-/3-, NaOH, Tween 20 were purchased from Merck. Phosphate buffer saline (PBS) solution of 0.1 M with 0.1 M KCl was used as the supporting electrolyte and it was prepared with K₂HPO₄ and KH₂PO₄, adjusted to the mentioned values of pH with either NaOH or HCl.
The electrochemical experiments were performed using an AUTOLAB PGSTAT 302N (EcoChemie, Netherlands) equipped with the associated NOVA 1.10 software. All the SPEs with a silver pseudo reference, a carbon counter electrode and with different working electrodes: graphite-based, graphite-based modified with GPH and MWCNTs, were provided by Metrohm (Spain). The data analysis and the creation of figures were performed using the Origin 8.5 software (OriginLab, United States). For a better visualization, all the SWV voltammograms presented here were baseline-corrected using the moving average filter included in the NOVA 1.10 software (window size 1), without affecting the results.

All reagents were of analytical grade and were used as received. All solutions were prepared with ultrapure water (18.2 MΩ, Millipore Simplicity). Cefalexin monohydrate, ceftriaxone sodium salt, cefadroxil monohydrate, cefotaxime sodium salt, cefaclor monohydrate, cefuroxime sodium salt, ceftazidime pentahydrate were provided by Antibiotice SA (Iași, Romania).
Ampicillin trihydrate, monosodium Hexaammineruthenium(III) chloride ([Ru(NH3)6]Cl3), 1,1′-Ferrocenedimethanol, HCl, Na₂HPO₄, NaH₂PO₄, NaCl, I3AA were purchased from Merck; K₄[Fe(CN)₆], K₃[Fe(CN)₆] and disodium phosphate, sodium dodecyl sulfate and methanol from Sigma-Aldrich (St. Louis, MO, USA), phosphoric acid, acetaminophen and ascorbic acid were purchased from Merck (Whitehouse Station, NJ, USA).
Capsules containing 500 mg cefalexin (Cefalexina Atb^® (Antibiotice SA)) and Someș River water collected near Cluj-Napoca, Romania were used for real samples analysis.

All chemicals used were of analytical grade and used as received without any further purification. All solutions were prepared with deionised water of resistivity not less than 18.2 MΩ cm from a Milli-Q Integral 3 system from Millipore UK (Watford, UK). Hexaamineruthenium (III) chloride (RuHex, 98%), castor oil, potassium ferricyanide (99%), potassium ferrocyanide (98.5–102%), sodium hydroxide (>98%), potassium chloride (99.0–100.5%), acetaminophen (≥99.0%), and phosphate-buffered saline (PBS) tablets were purchased from Merck (Gillingham, UK). (R)-Phenylephrine hydrochloride was purchased from TCI Chemicals (Zwijndrecht, Belgium). Carbon black (Super P®, >99+%) was purchased from Fisher Scientific (Loughborough, UK). Multi-walled carbon nanotubes (MWCNT, 10–30 μm length, 10–20 nm outer diameter) were purchased from Cheap Tubes (VT, USA). Recycled poly(lactic acid) (rPLA) was purchased from Gianeco (Turin, Italy). Commercial conductive PLA/carbon black filament (1.75 mm, ProtoPasta, Vancouver, Canada) was purchased from Farnell (Leeds, UK). Recycled non-conductive PLA filament was produced in-house, as shown previously [28 (link)]. Real samples of pharmaceuticals Max Strength Cold & Flu Capsules (Optipharma), Max Strength Cold & Flue Relief powder (Sainsbury’s), and Cold & Flu Powder (Beechams) were obtained from local convenience stores.

Standard solutions of heavy metals (1000 mg L⁻¹ Bi³⁺, Pb²⁺, Cd²⁺ and Zn²⁺) suitable for atomic-absorption spectrometry, ≥99.0% acetaminophen, 99.9% dopamine hydrochloride, sodium dodecyl sulfate, sodium decyl sulfate, sodium octyl sulfate, cetylpyridinium chloride (CPC), polyvinyl chloride (PVC) and tetrahydrofuran (THF) from Merck (Darmstadt, Germany) were used to demonstrate electroanalytical usefulness of shungite electrodes. Sodium hydroxide, 98.5% boric acid, 85% phosphoric acid, glacial acetic acid, di-sodium hydrogen phosphate 12-hydrate, 98.5% sodium dihydrogen phosphate dihydrate and 99% sodium acetate anhydrous from Lach-Ner s.r.o. (Neratovice, Czech Republic) were chosen for preparation of Britton–Robinson buffer (BRB) of 0.1 mol L⁻¹, phosphate buffer (PB) of pH 7 and acetate buffer (AcB) of pH 4.5. All these working solutions were prepared using deionized water with resistivity of 18.3 MΩ cm, which was obtained from the Millipore Milli-Q^®® purification unit from Merck (Darmstadt, Germany).