Simultaneous and sensitive determination of ascorbic acid and tryptophan on ionic liquid/nanocomposite modified carbon paste electrode

Ascorbic acid (AA), also known as vitamin C, is very popular for its antioxidant property, and present in the human diet as a vital vitamin. It is needed for many functions in the body,including helping the body use carbohydrates, fats, and protein [1]. Moreover, it is also used for the prevention and treatment of senility, the common cold, treating asthma, some mental illness, infertility, allergies, eye ulcers, blood clots, gum disease, pressure sores and AIDS. Tryptophan(Trp), as an essential amino acid for the human body and a vital constituent of protein biosynthesis of living organisms is important in nitrogen balance and the maintenance of muscle mass and body weight in humans [2]. It is well known that ascorbic acid and tryptophan areusually co-existing substances in biological matrixes and abnormal levels of these species will lead to several diseases and disorders. Therefore, to establish a simple, accurate, rapid and inexpensive method for simultaneous detection of AA and Trp in food, pharmaceutical productsand biological fluids is very necessary. The room temperature ionic liquids (RTILs) modified carbon paste electrodes (CPEs) has shown higher electron rate transfer compared to that of bare CPE [3]. Moreover, RTIL has been shown to be suitable media for supporting biocatalyticprocessing. Nowadays, there is wide interest in the fabrication of nanocomposite particles with unparalleled and tailored properties for various applications in material science [4]. In this paper, MWCNT/Fe3O4@SiO2 based electrochemical sensor was fabricated for the simultaneous determination ofascorbic acid (AA) and tryptophan (Try), which is very important in the clinical diagnosis. Electrochemical studies were carried out by using cyclic voltammetry (CV), square wave voltammetry(SVW) and chronoamperometry (CHA). The experiment results showed good linear response range fordetection of AA and Trp and the detection limits were 0.1 μM and 5 μM (S/N=3). Moreover, the modified electrode exhibited excellent stability and reproducibility. The analytical performance of this sensor was also demonstrated for the determination of ascorbic acid in commercial pharmaceutical samples such as tablets and injections of vitamin C. The applicability of this sensor was also extended in the determination of tryptophan in spiked samples

Keywords:

Ascorbic acid , Tryptophan , Nanocomposite , Ionic liquid , Modified electrode