| Bisphenol A (BPA) is a kind of environmental hormones with severe toxic effects such as disrupting endocrine system or causing cancer. Ascorbic acid (AA), uric acid (UA) and xanthine (XA) are important biomicromolecules, and many diseases are associated with their concentrations. Therefore, it is of great scientific significance to develope sensitive, rapid and simple method for their determination. In this paper, we establish novel electrochemical methods for the sensitive determination of BPA as well as for the simultaneous determination of AA, UA and XA utilizing the distinctive properties of mesoporous materials and modified carbon paste electrode. The main researches were summarized as follows:1,In NaOH, a kind of mesoporous silica (MCM-41) was synthesized using CTAB as the template and TEOS as the inorganic precursor. The resulting MCM-41 was characterized using scanning electron microscopy and infrared spectrometry. After that, MCM-41 was used to modify the carbon paste electrode (CPE). Moreover, silica gel, carbon nanotubes and activated carbon were also employed to fabricate modified CPEs for comparative studies. The electrochemical properties were investigated using K3[Fe(CN)6] as the electrochemical probe. It was found that MCM-41 not only remarkably improves the electrode area, but also facilitates the electron transfer of K3[Fe(CN)6]. This reveals that MCM-41 exhibits more excellent electrochemical sensing properties. The electrochemical behaviors of BPA were examined. Compared with other modified electrodes, the MCM-41 modified electrode significantly increases the oxidation signals of BPA, showing remarkable surface enhancement effects. The influences of supporting electrolyte, accumulation time and content of MCM-41 on the oxidation peak currents of BPA were studied. Thus, a novel electrochemical method was proposed for the determination of BPA. The limit of detection is 3.8×10-8 mol L-1, and the linear range is from 2.2×10-7 to 8.8×10-6 mol L-1. Finally, the proposed method was employed to determine BPA in water samples, and the recovery is in the range from 91.3% to 107.2%.2,Using CTAB as the structure-directing template, Al-doped mesoporous silicas (Al/MCM-41) with different Si/Al molar ratios such as 30, 15 and 5 were synthesized using TEOS and NaAlO2 as the source of Si and Al. Meanwhile, the mesoporous silica (MCM-41) was also prepared in the absence of NaAlO2. After that, they were used to construct the modified carbon paste electrodes. The electrochemical behavior of AA, UA and XA were studied. It was found that MCM-41, Si:Al=30/MCM-41 and Si:Al=15/MCM-41 significantly increase the oxidation peak currents of AA, UA and XA, indicative of considerable enhancement effects. However, Si:Al=5/MCM-41 does not exhibit the enhancement effects. In pH 7.0 phosphate buffer, the electrochemical behaviors of coexistence of AA, UA and XA were examined. At the unmodified CPE, the oxidation peaks of AA and UA were overlapped. However, three independent oxidation peaks were observed at 0.02 V, 0.25 V and 0.62 V at the MCM-41 modified CPE. Further studies show that their oxidation has no mutual interference, meeting the demand of simultaneous determination. As a result, a sensitive, rapid and convenient electrochemical method was developed for the simultaneous determination of AA, UA and XA. The limits of detection are 3.0×10-6 mol L-1, 1.2×10-7mol L-1 and 1.3×10-6 mol L-1, respectively. The new method was used to determine the content of AA, UA and XA in serum sample, and satisfactory recovery was achieved. |
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