Simple and direct electrochemical detection of rosmarinic acid in food samples based on nanochannel modified carbon electrode

Abstract

The detection of rosmarinic acid (Ros A) in food samples holds major significance. Simple and convenient electrochemical detection of Ros A with high performance remains a challenge. In this work, a nanochannel array-modified carbon electrode was constructed using a simple and convenient approach to achieve highly sensitive electrochemical detection of Ros A in food samples. Through simple electrochemical pre-activation of a glassy carbon electrode (GCE), oxygen-containing functional groups were introduced on the electrode surface (p-GCE). Vertically-ordered mesoporous silica film (VMSF) was stably grown on p-GCE through electrochemical-assisted self-assembly (EASA) without the introduction of another adhesive layer (VMSF/p-GCE). Transmission electron microscopy (TEM) characterization demonstrated the highly ordered structure of VMSF with a nanochannel diameter around 2.7 nm. Both p-GCE and the nanochannels significantly enhanced the electrochemical signals of Ros A on the electrode, exhibiting dual signal amplification. VMSF/p-GCE demonstrated sensitive detection of Ros A with a linear range of 500 nM to 1 μM and 1 μM to 35 μM. The detection limit (DL) was 26 nM. Combining the good anti-fouling and anti-interference properties of the nanochannels, VMSF/p-GCE can achieve direct electrochemical detection of Ros A in food samples. The sensor can be easily regenerated for repeated use. The simple fabrication, high detection sensitivity and selectivity of the sensor make it a new strategy for rapid preparation of high-performance electrochemical sensors.

Fig. 1. Schematic illustration for the fabrication of VMSF/p-GCE sensor (A), the anti-fouling/anti-interference properties of nanochannel in real sample (B) and the electrochemical process Ros A on electrode (C).

Fig. 2. High-resolution C 1s XPS spectra of bare GCE (A), the electrode obtained after anodic polarization (B), and p-GCE (C).

Fig. 3. (A) Top-view TEM image of VMSF at different magnification. Inset is the corresponding high-resolution transmission electron microscope (HRTEM) image. The hexagon represents a hexagonal stacking of nanochannels. (B) TEM image of cross-section of VMSF. (C) SEM image of top-view of VMSF/p-GCE.

Fig. 4. CV curves obtained on different electrodes in Fe(CN)₆^3−/4− (A) or Ru(NH₃)₆³⁺ (B) solution.

Fig. 5. CV curves (A) and DPV curves (B) obtained on different electrodes in 0.1 M PBS (pH = 7) without or with Ros A (20 μM) at a scan rate of 50 mV s⁻¹. Insets show the corresponding CV or DPV curves obtained on GCE in the presence or absence of Ros A.

Fig. 6. (A) The current of (10 μM) Ros A obtained on VMSF/p-GCE constructed using different VMSF growth time. (B) DPV curves obtained on VMSF/p-GCE in Ros A (20 μM) at different pH values. The inset shows the linear dependence between anodic peak potential and pH. (C) CV curves obtained on VMSF/p-GCE in PBS (0.01 M, pH = 7) containing Ros A (10 μM) at different scan rate (40, 60, 80, 100, 120, 140, 160, 180, 200 mV s⁻¹ from outside to inside), the inset is the relationship between peak current and scan rate. (D) Effect of enrichment time on the current response of Ros A (10 μM) in 0.1 M PBS (pH = 7). The error bars represent the standard deviations of three measurements.

Fig. 7. (A) DPV curves obtained on VMSF/p-GCE in 0.1 M PBS solution (pH = 7) containing different concentrations of Ros A. (B) The corresponding calibration curve between the DPV curves and the concentration of Ros A. Inset is the amplified view of the DPV curves in the low-concentration region. The error bars represent the standard deviations of three measurements.

Fig. 8. (A and B) The current ratio (I/I₀) obtained from VMSF/p-GCE for detection of Ros A (20 μM) in the absence (I) and presence (I₀) of the added interfering species. The concentration of interfering species is 100 μM. (C) The peak current ratio of Ros A (20 μM) on p-GCE or VMSF/p-GCE in absence (I₀) or presence (I) of 10 μM BSA or DNA in PBS (0.1 M, pH = 7). (D) The regeneration of VMSF/p-GCE.

Fig. 9. Determination of Ros A in rosemary tea (A) and leaching solution of rosemary powder (B) using the extrapolation of the standard addition method.