Additively manufactured electrodes for the electrochemical detection of hydroxychloroquine

Abstract

Although studies have demonstrated the inactivity of hydroxychloroquine (HCQ) towards SARS-CoV-2, this compound was one of the most prescribed by medical organizations for the treatment of hospitalized patients during the coronavirus pandemic. As a result of it, HCQ has been considered as a potential emerging contaminant in aquatic environments. In this context, we propose a complete electrochemical device comprising cell and working electrode fabricated by the additive manufacture (3D-printing) technology for HCQ monitoring. For this, a 3D-printed working electrode made of a conductive PLA containing carbon black assembled in a 3D-printed cell was associated with square wave voltammetry (SWV) for the fast and sensitive determination of HCQ. After a simple surface activation procedure, the proposed 3D-printed sensor showed a linear response towards HCQ detection (0.4-7.5 μmol L^-1) with a limit of detection of 0.04 μmol L^-1 and precision of 2.4% (n = 10). The applicability of this device was shown to the analysis of pharmaceutical and water samples. Recovery values between 99 and 112% were achieved for tap water samples and, in addition, the obtained concentration values for pharmaceutical tablets agreed with the values obtained by spectrophotometry (UV region) at a 95% confidence level. The proposed device combined with portable instrumentation is promising for on-site HCQ detection.

Keywords: Additive manufacturing; Electroanalysis; FDM; Fused filament fabrication; Sensors.

Graphical abstract

Fig. 1

Molecular structure of HCQ.

Fig. 2

Real images of components of the 3D-printed cell (top view): (a) body cell; (b) top cover; (c) bottom cover; (d) screw; (e) 3D-printed CB-PLA working electrode; (f and g) top and front views of assembled 3D-printed cell.

Fig. 3

Cyclic voltammetric profiles obtained for 28 μmol L⁻¹ HCQ at the 3D-printed CB-PLA electrode before (black line) and after electrochemical treatment (red line), using 0.12 mol L⁻¹ BR buffer (pH = 7.0). The dashed lines are the respective blanks. Voltammetric conditions: scan rate: 50 mV s⁻¹; step potential: 5 mV. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 4

(A) Cyclic voltammetric responses obtained for 28 μmol L⁻¹ HCQ in 0.12 mol L⁻¹ BR buffer of different pHs (purple line, pH = 6.0); (green line, pH = 7.0); (blue line, pH = 8.0); (red line; pH = 9.0); (black line, pH = 10.0). (B) Relation between pH and peak potential (E_p) for the first (black line) and second (red line) oxidation processes of HCQ. Voltammetric parameters: scan rate of 50 mV s⁻¹ and step potential of 5 mV. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 5

(A) Cyclic voltammetric responses obtained for 28 μmol L⁻¹ HCQ in 0.12 mol L⁻¹ BR buffer (pH = 9.0) varying scan rates (10–150 mV s⁻¹). (B) Relationship of the peak potential (Ep) as a function of the log ν for the first (black line) and second (red line) electrochemical processes. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 6

Baseline-corrected SWV responses obtained for increasing concentrations (0.4–15 μmol L⁻¹) of HCQ using 0.12 mol L⁻¹ BR buffer (pH = 9.0) at 3D-printed CB-PLA electrodes and respective calibration plot (inset in Fig. 4). SWV conditions: amplitude = 70 mV; step potential = 4 mV; frequency = 30 s⁻¹.

Fig. 7

Baseline-corrected SWV responses for the analysis of (A) pharmaceutical tablet (sample A) and (B) spiked tap water (sample A) samples diluted in 0.12 mol L⁻¹ BR buffer (pH = 9.0) before (supporting electrolyte, dashed line) and after additions of sample (red line) and respective increasing concentrations of HCQ (green, dark blue and light blue lines). Inset: the respective calibration plots. SWV conditions: amplitude = 70 mV; step potential = 4 mV; frequency = 30 s⁻¹. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)