Leather Shaving Waste Extract as an Electrochemical Modifier at a Pencil Graphite Electrode for Paracetamol Determination in Pharmaceuticals

Abstract

A simple, facile, and sensitive method based on leather shaving waste extract (LSWE) modified pencil graphite electrode (PGE) was developed to determine paracetamol (PAR) by employing the square wave adsorptive stripping voltammetry (SW-AdSV) technique. Leather shaving waste (LSW) was characterized by energy-dispersive X-ray spectroscopy and by investigating its morphology by taking scanning electron microscopy (SEM) images. The extraction process was conducted on an LSW by utilizing acetonitrile. Furthermore, the extraction ratio of LSW to acetonitrile was optimized and found to be 0.1 g LSW/10 mL acetonitrile at room temperature for an extraction period of 12 h. Modification of PGE by 0.1 g of LSWE (0.1LSWE/PGE) was done by performing cyclic voltammetry (CV) at the potential range 0-(+2.3) V for 10 cycles, followed by a characterization process of 0.1LSWE/PGE by employing CV, electrochemical impedance spectroscopy, and SEM techniques. PAR determination parameters at 0.1LSWE/PGE were optimized and found to be an accumulation time of 35 s in Britton Robinson buffer solution at pH 1.8. A linear relationship (r ² = 0.997) was observed between peak current and PAR concentration within the range 5-100 μM, with a sensitivity of 196.46 μA μM^-1 cm^-2. The limit of detection and limit of quantification were found to be 1.6 and 4.51 μM, respectively. Neglected interferant influence on the determination of PAR at 0.1LSWE/PGE was observed in the presence of dopamine, uric acid, caffeine, ascorbic acid, Na⁺, K⁺, Mg²⁺, Ca²⁺, NO₃ ^-, and Cl^- ions. In order to evaluate 0.1LSWE/PGE in the determination of PAR in real pharmaceutical samples, different common PAR-containing pharmaceuticals in Türkiye were analyzed, achieving a recovery range of 99.76-102.87%.

Figure 1

PAR chemical structure.

Figure 2

SEM images for LSW at different magnifications. (A) 1000×, (B) 5000×, and (C) 50,000×.

Figure 3

(A) EDX spectrum for LSW. (B–E) Corresponding element mapping images of O, C, Cr, and N for LSW, respectively.

Figure 4

IR spectra for (A) 0.1LSWE, (B) 0.2LSWE, (C) 0.3LSWE, (D) 0.4LSWE, and (E) 0.5LSWE.

Figure 5

(A) Cyclic voltammogram of 0.1LSWE in the presence of 100 mM NBu₄BF₄ versus Ag/Ag⁺/(10 mM AgNO₃) on PGE at the potential range from 0 to +2.3 V for 10 cycles. Inset: voltammogram of the first cycle. (B) Cyclic voltammogram of acetonitrile versus Ag/Ag⁺/(10 mM AgNO₃) on PGE at the potential range from 0 to +2.3 V for 10 cycles.

Figure 6

(A) Cyclic voltammogram of 1 mM ferrocene in acetonitrile in the presence of 100 mM NBu₄BF₄ at 0.1, 0.2, 0.3, 0.4, and 0.5LSWE/PGEs and PGE. Bar charts of relevant current densities of 0.1, 0.2, 0.3, 0.4, and 0.5LSWE/PGEs and PGE for (B) anodic and (C) cathodic peaks.

Figure 7

Nyquist type impedance curves of 0.1, 0.2, 0.3, 0.4, 0.5LSWE/PGEs and PGE in a mixture of 1 mM ferricyanide/ferrocyanide Fe(CN)₆^3–/4– solutions in the ratio (1:1) prepared in 100 mM KCl at frequency range 100.000–0.05 Hz and 10 mV wave amplitude.

Figure 8

SEM images for (A) PGE and (B) 0.1LSWE/PGE.

Figure 9

SW-AdS voltammograms of 100 μM PAR in BR buffer solution at pH 1.8 and 35 s accumulation time at 0.1LSWE/PGE and PGE.

Figure 10

(A) LS voltammograms of 1 mM PAR in BR buffer solution at pH 1.8 and accumulation time 35 s by applying different scan rates 10, 25, 50, 100, 150, and 200 mV s^–1. (B) Plot of peak current versus square root of the scan rate. (C) Plot of peak current versus scan rate. (D) Plot of log peak current versus log scan rate. (E) Plot of peak potential versus log scan rate.

Figure 11

(A) SW-AdS voltammograms of 1 mM PAR in different pHs of BR buffer solution of 1.8, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0 and accumulation time of 35 s at 0.1LSWE/PGE. (B) Relevant curve of peak current (μA) versus pH. (C) Relevant curve of peak potential (mV) versus pH. (D) SW-AdS voltammograms of 1 mM PAR in different pHs of BR buffer solution of 1.8, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0 and accumulation time of 35 s at PGE.

Figure 12

(A) SW-AdS voltammograms of 100 μM PAR in BR buffer solution pH 1.8 at different accumulation times 0, 5, 10, 15, 20, 25, 30, 35, 40, and 45 s at 0.1LSWE/PGE. (B) Relevant plot of peak current (μA) versus accumulation time (s).

Figure 13

(A) SW-AdS voltammograms of PAR at different concentrations of 5, 7.5, 10, 25, 50, 75, and 100 μM in BR buffer solution at pH 1.8 and 35 s accumulation time at 0.1LSWE/PGE. (B) Relevant standard curve of peak current (μA) versus PAR concentration (μM).

Figure 14

SW-AdS voltammograms of PAR containing pharmaceuticals prepared in BR buffer solutions at pH 1.8 by applying 0.1LSWE/PGE and an accumulation time of 35 s and a scan rate of 100 mV s^–1.