Indirect Determination of Alkaline Phosphatase Based on the Amperometric Detection of Indigo Carmine at a Screen-Printed Electrode in a Flow System

Abstract

Amperometric analysis of indigo carmine at a bare screen-printed electrode placed in an FIA system is reported. This compound is easily detected at a potential of -0.3 V (vs. Ag pseudo-reference electrode) without observing any fouling of the electrode surface, thus allowing the repetitive use of the same electrode in a reproducible manner (coefficients of variation down to 7% for more than 20 consecutive determinations). A linear range of three orders of magnitude and a limit of detection in the sub-micromolar range were attained for this molecule. Based on these studies, indirect amperometric measurements of alkaline phosphatase (ALP) activity in solution were easily carried out using 3-indoxyl phosphate substrate. Its hydrolysis catalyzed by ALP gave rise to indigo product. This product is insoluble in aqueous solutions but it was easily converted into its soluble parent compound, indigo carmine, by addition of fuming sulfuric acid to the reaction media. Using this approach, we achieved a linear range of more than one order of magnitude and a limit of detection of 1 U/l ALP, for an enzymatic reaction time of 60 min.

In vivo human electrochemical properties of a NiTi‐based alloy (Nitinol) used for minimally invasive implants

“…Although their potential is unknown and depends on the solution composition, they do provide a constant potential value. The simplicity, facile design and processability of such type of electrodes have made them attractive in electrochemical systems used in the monitoring of corrosion and redox processes at high temperatures, 33 impedance spectroscopy measurements, 34,35 biosensors, 36,37 screenprinted electrodes, 38,39 and potentiometric, 40 and voltammetric 41 determinations. For in vivo measurements, pseudo-reference electrodes are used in substitution to the conventional saturated calomel (SCE) and Ag/AgCl reference electrodes.…”

Electrochemical analysis of indigo carmine using polyarginine modified carbon paste electrode

“…IC is also utilized in medical diagnosis apart from its use as an additive in pharmaceutical tablets and capsules [12]. Presence of IC in environment and real samples has to be traced, because IC ingestion can affect the liver, central nervous system, kidneys and eyes [13,14]. Therefore, it is proposed obligatory to identify the concentration of IC in a variety of natural samples.…”

Chapter 26 Thick- and thin-film DNA sensors

“…Its sulfonation in acidic medium gives rise to IC, an aqueous soluble compound that shows an electrochemical behaviour similar to indigo blue. Both 3-IP and IC have already been studied on SPCEs [55,56]. However, although these genosensors are stable and sensitive devices for the detection of specific nucleic acid fragments, the need of two additional steps to obtain the analytical signal resulted in a large timeconsuming analysis.…”