Isatin Analysis Using Flow Injection Analysis with Amperometric Detection – Comparison of Tetrahedral Amorphous Carbon and Diamond Electrode Performance

Abstract

Isatin is an endogenous indole compound in humans and rodents that has a wide range of biological activity. In rat models, isatin concentrations have been shown to increase in the heart, brain, blood plasma, and urine with stress. Studies on patients suffering from Parkinson's disease have indicated a correlation between progress of the disease and urinary output of the molecule. Isatin is electrochemically active and can therefore be detected with electrochemical techniques. In this work, we compared the performance of a nitrogen‐incorporated tetrahedral amorphous carbon (ta‐C:N) and a boron‐doped nanocrystalline diamond thin‐film electrode for the oxidative detection of this biomolecule using flow injection analysis with amperometric detection. The measurements were performed in 0.1 phosphate buffer pH 7.2. The ta‐C:N electrode, like boron‐doped nanocrystalline diamond, exhibits some excellent properties for electroanalytical measurements including (i) low background current and noise, (ii) microstructural stability at positive detection potentials, and (iii) good activity for a wide range of bioanalytes without conventional surface pretreatment. The results reveal that both electrodes exhibit a linear dynamic range from 100 to 0.1 μmol L−1, a short‐term response variability 3–4 % RSD (30 injections), a sensitivity of 18 mA M‐1, and a limit of detection (S/N=3) of 1.0×10−7 mol L−1 (14 ng mL−1 or 2.5 fmol).

Amplified Anodic Electrogenerated Chemiluminescence of Tris(2,2′‐bipyridyl)ruthenium(II) for the Sensitive Detection of Isatin

“…For example, Qi et al has reported the cathodic lucigenin ECL detection of isatin at a Pt electrode . Swain's group has detected isatin at tetrahedral amorphous carbon electrode by amperometry combined with a flow injection analysis . Rusinek's group reported the electrochemical detection of isatin using a fabricated two 3‐in‐1 boron‐doped diamond (BDD) electrodes .…”

HPLC−EC Analysis of Estrogenic Compounds: A Comparison of Diamond and Tetrahedral Amorphous Carbon Electrode Performance

“…However, polishing is a tedious and time‐consuming process. Furthermore, glassy carbon is subject to surface fouling and typically undergoes unwanted microstructural changes at the very positive potentials often required to detect target pharmaceuticals and pollutants, like the estrogenic metabolites .…”

“…In general, diamond electrodes have emerged as promising alternatives, due to their chemical inertness and high stability . Planar boron‐doped diamond (BDD) thin‐film electrodes have been studied extensively in recent years, and exhibit key properties of resistance to fouling, low background current, and wide working potential window . Structurally, BDD consists entirely of sp 3 hybridized carbon, and is doped with diborane gas (B 2 H 6 ) during thin film growth to increase electrical conductivity .…”

“…Nitrogen‐incorporated tetrahedral amorphous carbon (t a ‐C : N) is a new type of thin‐film electrode material . t a ‐C : N is composed of a mixture of sp 2 and sp 3 ‐bonded carbon, along with nitrogen impurities added during growth .…”

“…The fraction of sp 2 carbon and the electrical conductivity increase with increasing nitrogen incorporation . Importantly, t a ‐C : N exhibits many of the same properties as BDD, such as microstructural stability at high potentials, low background current and resistance to molecular adsorption . Moreover, t a ‐C : N thin films can be deposited at or near room temperature (25–100 °C).…”