# Highly Sensitive Square Wave Adsorptive Stripping Voltammetric Determination of Dopamine in Human Plasma Using a Cytosine-Modified Pencil Graphite Electrode

## TL;DR

This paper presents a low-cost, sensitive method to detect dopamine in human plasma using a modified pencil graphite electrode.

## Contribution

A novel cytosine-modified pencil graphite electrode is introduced for highly sensitive dopamine detection.

## Key findings

- The CT/PGE showed a linear response for dopamine from 0.1 mM to 7.5 nM.
- The method achieved a detection limit of 2.28 nM and quantification limit of 6.85 nM.
- The technique was successfully applied to human plasma samples.

## Abstract

Dopamine (DA) is
an essential neurotransmitter in the central nervous
system, playing a vital role in the human brain. A simple, facile,
fast, and low-cost method based on the cytosine-modified pencil graphite
electrode (CT/PGE) was developed to determine dopamine (DA) by using
the square wave adsorptive stripping voltammetry (SWAdSV) technique.
The cytosine (CT) was modified on the bare pencil graphite electrode
(PGE) by conducting cyclic voltammetry (CV) over a potential range
between +0.7 and +1.9 V for 10 cycles. A number of techniques including
CV, electrochemical impedance spectroscopy (EIS), and field-emission
scanning electron microscopy (FE-SEM) were used to characterize the
CT/PGE. The impact of varying pH values (6.4, 6.8, 7.2, 7.6, and 8.0)
and phosphate buffer solution (PBS) on the DA determination was studied
using the square wave voltammetry (SWV) technique. The basic voltammetric
techniques SWV, SWAdSV, differential pulse voltammetry (DPV), and
differential pulse adsorptive stripping voltammetry (DPAdSV) were
used to determine the most suitable method for analytical applications.
The accumulation time was optimized using the SWAdSV technique on
the CT/PGE, within a potential range of −0.4 to +0.4 V. The
CT/PGE was evaluated in the presence of several interferents, such
as urea, ascorbic acid, and uric acid. Under optimum conditions, the
CT/PGE exhibited a well-defined linear relationship for DA across
the concentration ranges of 0.1 mM to 0.5 μM and 0.1 μM
to 7.5 nM, with a limit of detection (LOD) of 2.28 nM and a limit
of quantification (LOQ) of 6.85 nM. The suggested method was effectively
applied to the determination of DA in human plasma serum samples to
evaluate its suitability.