RESUMEN
A simple, accurate, and environmentally friendly method for the simultaneous determination of the analog endocrine disruptors bisphenol S (BPS) and bisphenol A (BPA) was developed and validated. The determination was performed by square-wave voltammetry using a cathodically pretreated boron-doped diamond (BDD) as the working electrode, with 0.1 mol L-1 H2SO4 as the supporting electrolyte. Under optimized conditions, a wide linear working range (R2 = 0.999) from 0.20 to 80.0 mg L-1 with a limit of detection (S/N = 3) of 0.060 mg L-1 was attained for BPS. For BPA, a linear correlation (R2 = 0.992) was attained from 0.10 to 50.0 mg L-1, with a limit of detection of 0.030 mg L-1. As far as we could ascertain, these are the lowest limits of detection and the widest linear ranges in the literature for this determination. The method was applied to the simultaneous determination of BPS and BPA in real water samples, with minimum sample preparation processes (dilution and acidification only). Excellent recovery values were achieved, ranging from 95 to 99%. Additionally, the method was successfully applied to the monitoring of the electrochemical degradation (anodic oxidation) of BPS using a recirculating flow system fitted with a BDD anode. The decay of [BPS] with time was also checked by an HPLC method, with results statistically similar to those obtained by the proposed electroanalytical method. Hence, the proposed method is a reliable, greener, and low-cost alternative to monitor simultaneously BPS and BPA in aquatic matrices or only BPS in wastewater treatment processes.
RESUMEN
Boron-doped diamond (BDD) electrodes present several notable properties, such as the largest potential window of all electrode materials (especially in anodic potentials), low background and capacitive currents, reduced fouling compared to other electrodes, mechanical robustness, and good stability over time. On the other hand, flow-based systems are known as well-established approaches to minimize reagent consumption and waste generation and with good compromise between sample throughput and analytical performance (mechanization of chemical assays). This review focuses on the use of BDD electrodes for electrochemical detection in flow systems, such as flow injection analysis (FIA), batch injection analysis (BIA), high performance liquid chromatography (HPLC), and capillary electrophoresis (CE). The discussion deals with the historical evolution of BDD, types of electrochemical pre-treatments (cathodically/H-terminated or anodically/O-terminated), cell configurations, and analytical performance. Articles are discussed in chronological order and subdivided according to the type of flow system: FIA, BIA, HPLC, and CE.
RESUMEN
In this work, a batch-injection analysis system with square-wave voltammetric (BIA-SWV) detection was applied for the first time to the simultaneous determination of inorganic (zinc) and organic (naphazoline) species. Both compounds were detected in a single run (70 injections h(-1)) with a small injection volume (â¼100 µL). The calibration curves exhibited linear response range between 3.0 and 21.0 µmol L(-1) (r=0.999) for naphazoline and between 10.0 and 60.0 µmol L(-1) (r=0.992) for zinc. The detection limits were 0.13 and 0.04 µmol L(-1) for zinc and naphazoline, respectively. Good reproducibility was achieved for multiple measurements of a solution containing both species (RSD<1.0%; n=20). The results obtained with the BIA-SWV method for the simultaneous determination of naphazoline and zinc were compared to those obtained by HPLC (naphazoline) and by FAAS (zinc); no statistically significant differences were observed (95% confidence level).
RESUMEN
In this work, the possibility of simultaneous determination of three compounds with a single-injection step using batch injection analysis with multiple pulse amperometric detection (BIA-MPA) is demonstrated for the first time. A sequence of three potential pulses (+1.25 V, +1.60 V, and +1.80 V) was applied with the acquisition of three separate amperograms. 8-Chlorotheophylline was detected selectively at +1.25 V, both 8-chlorotheophylline and pyridoxine at +1.60V and 8-chlorotheophylline, pyridoxine, and diphenhydramine at +1.80 V. Subtraction between the currents detected at the three amperograms (with the help of correction factors) was used for the selective determination of pyridoxine and diphenhydramine. The proposed method is simple, inexpensive, fast (60 injections h(-1)), and present selectivity for the determination of the three compounds in pharmaceutical samples, with results similar to those obtained by HPLC (95% confidence level).