Simultaneous electrochemical detection of hydroquinone, resorcinol, and salicylic acid using novel MWCNT-OH/TiO2/chitosan nanofibers composite sensor.

In this work, we have developed a novel electrochemical sensor based on a composite of hydroxylated multiwalled carbon nanotubes (MWCNT-OH), titanium dioxide (TiO2), and chitosan nanofibers, which was deposited onto the surface of a glassy carbon electrode (GCE) for the simultaneous detection of hydroquinone (HQ), resorcinol (RS), and salicylic acid (SA). The composite of MWCNT-OH/TiO2/Chitosan nanofibers was characterized using Fourier-transform infrared spectroscopy (FTIR), field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDS), Transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) techniques. The optimal composition ratio of MWCNT-OH, TiO2, and chitosan nanofibers obtained from the mixture design was 0.76:0.04:0.2 (v/v), while the optimal pH condition for the simultaneous detection of HQ, RS, and SA was pH 6. A synergistic effect was observed in the GCE/MWCNT-OH/TiO2/chitosan nanofibers system, which exhibited an effective surface area 17 times that of the bare electrode. The sensor demonstrated high linear responses toward HQ (0.5-50 μM), RS (20-250 μM), and SA (20-250 μM) in simultaneous detection. The values of the limit of detection (LOD) (S/N ≈ 3) for HQ, RS, and SA were 0.0021 ± 0.0002, 0.0167 ± 0.0011, and 0.0193 ± 0.0004 μM, respectively. In addition, the values of the limit of quantification (LOQ) (S/N ≈ 10) for HQ, RS, and SA were 0.0070 ± 0.0007, 0.0556 ± 0.0036, and 0.0642 ± 0.0130 μM, respectively. The electrochemical performances also showed high reproducibility, stability, and selectivity. Thus, the sensor provides reliable simultaneous in situ detection in skincare samples, consistent with standard methods.