Fast and Selective Microfluidic Chips for Electrochemical Antioxidant Sensing in Complex Samples

Abstract

In this work, capillary electrophoresis chips with electrochemical detection have been assessed as creative and selective microfluidic platforms to integrate and simplify on a microscale the traditional methods for complex natural antioxidants determination. Depending on the acid-base properties of the analytes, two approaches (class-selective electrochemical index determination (CSEID) and individual antioxidant determination (IAD)) were investigated for the analysis of nine antioxidants ((+)-catechin, rutin, quercetin, chlorogenic, ferulic, caffeic, protocatechuic, vanillic, and gallic acids) in food samples. First, the novel concept of a class-selective electrochemical index is proposed allowing a fast and reliable determination of the main antioxidant classes (flavonoids and phenolic acids) in less than 100 s. In addition, an impressive separation of nine antioxidants is also offered in less than 260 s with the individual antioxidant determination approach. Qualitative and quantitative performances of both approaches were studied. The analytical figures of merit (i.e., electroosmotic flow (EOF) precision as relative standard deviation (RSD), resolution, signal precision as RSD, limit of detection, limit of quantification, and accuracy as recovery) of both approaches were <4%, approximately 1, < or = 5%, <8 microM, 30 microM, between 91% and 104%, and <4%, < or = 2%, <9%, < or = 6 microM, < or = 20 microM (with the exception of protocatechuic acid, which shows values of 40 and 130 microM, respectively), between 80% and 107% for the CSEID and IAD concepts, respectively, which are excellent for food samples analysis. A set of representative samples was analyzed including apple and pear skins and pulps, red and white wines, and green tea tablets. High agreement was observed between the results of the sample analyses from the two microchip-based approaches, and good correlation was observed with results obtained from traditional methods. Although the prominent phenolic antioxidant classes and compounds were successfully determined, some nonprominent peaks were not detected in the samples when applying the IAD approach. Different integration strategies on microchip platforms were further explored, looking for a simplification of the overall analytical process without losing the excellent analytical characteristics obtained in both approaches. The results are promising and indicative of the progress of analytical microfluidics toward the "plateau of productivity" and the routine laboratory application.

In‐channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat

“…The combination of amperometric detection with ME provides a powerful approach to the determination of a variety of biologically important compounds including reactive oxygen species (ROS) [7], reactive nitrogen species (RNS) [8], catecholamines [9, 10], thiols [11, 12], and carbohydrates [13-15]. This technique has been used in a variety of applications including biomedical [16], agricultural [17], forensics [18, 19], and environmental analyses [20]. …”

Microfluidics for Monitoring Oxidative Stress and Antioxidant Capacity

“…However, the use of HPLC or CE for the separation of the antioxidant compounds require expensive equipments and rely on long separation times, high reagent consumption and complex manipulation steps that involve highly qualified personnel. Therefore, the development of systems integrating microfluidic and detection elements in a single, simple and cheap structure, with short analysis times and commercialization possibilities, appears to be the logical alternative to them [52]. In fact, several groups have been working in the development of microfluidic systems based on CE for the detection of antioxidants.…”

“…In this case, pyridoxine (B6), folic acid (B9) and ascorbic acid (C) could be separated with good resolution after only 130 s and accurately detected using glassy carbon disk electrodes. This structure was then applied to the fast and selective determination of complex natural antioxidants samples [52]. In this paper, authors proposed two approaches for the antioxidant capacity determination based on the acid-base properties of the antioxidants.…”

“…With permission from[52].Analytical approaches visualization. (A) class-selective electrochemical index determination (MES, pH = 5, 10 mM); (I) total flavonoids peak, (II) total phenolic acids peak (analyte concentration of the different compounds in all cases: 50 μM each).…”

Gold-nanosphere formation using food sample endogenous polyphenols for in-vitro assessment of antioxidant capacity

“…Therefore a convenient method for estimation of antioxidant content and evaluation of their antioxidant capacity is still desirable, and research is being conducted using novel approaches [6][7][8][9][10][11]. On the basis of the chemical reactions involved, the major antioxidant capacity assays can be approximately divided into two categories:…”