ANALYTICAL PLATFORMS FOR IN SITU MONITORING OF ENVIRONMENTAL OBJECTS BASED ON MICROFLUIDIC SYSTEMS

ABSTRACT

The paper discusses the analytical capabilities of micro-fluid systems based on native and modified screen-printed electrodes and a portable analyzer for conducting voltammetric analysis of a number of pollutants of the natural environment at the sampling site. The current-voltage curves obtained on screen-printed electrodes for Cu²⁺, Cd²⁺, Pb²⁺, Tl³⁺, Fe³⁺, Bi³⁺, Cr³⁺ ions are given.

Using the example of voltammetric analysis of the waters of the Zarafshan River, the possibility of using such a technique in the field, directly at the sampling site, is shown.

АННОТАЦИЯ

В работе рассматриваются аналитические возможности микрофлюидных систем на основе нативных и модифицированных screen-printed электродов и портативного анализатора для проведения вольтамперометрического анализа ряда поллютантов природной среды на месте отбора проб. Приводятся вольтамперные кривые, полученные на screen-printed электродах для ионов Cu²⁺, Cd²⁺, Pb²⁺, Tl³⁺, Fe³⁺, Bi³⁺, Cr³⁺.

На примере вольтамперометрического анализа вод реки Зарафшан показана возможность применения такой техники в полевых условиях, непосредственно на месте отбора проб.

Keywords: voltammetry, microfluidic systems, screen-printed electrodes, portable analyzer, in situ environmental monitoring.

Ключевые слова: вольтамперометрия, микрофлюидные системы, screen-printed электроды, портативный анализатор, мониторинг окружающей среды in situ.

Introduction

Miniaturization of measuring analytical platforms and maximum simplification of sample preparation are of crucial importance in monitoring environmental pollutants at the sampling site and in real time [1]. This problem can be solved with the use of microfluidic systems that reduce the volume of analytes by several orders of magnitude compared to traditional laboratory approaches, which, in turn, reduces the total cost of analysis by saving reagents.

In electrochemical methods of analysis, such microfluidic systems, which have been widely used in the last decade, include electrodes made by screen printing, called screen-printed electrodes [2,3].

The evolution of screen-printed electrode manufacturing methods has led to the creation of almost universal three-electrode systems suitable for any voltammetric analysis technique [4-7]. In these designs, the working and auxiliary electrodes are made of carbon-containing paste, and the Ag/AgCl reference electrode is made of silver, which are part of special ink for inkjet printers. Polyethylene terephthalate (PET) is usually used as the substrate material. The unification of the technical characteristics of screen-printed electrodes is achieved by using a constant composition of ink and a printing device.

The practice of mass production of such electrochemical sensors and the creation of miniature measuring instruments based on microprocessor technology brought the testers as close as possible to the cherished goal of conducting on–line and in situ analysis.

The purpose of this work is to demonstrate the analytical capabilities of microfluidic technology based on screen-printed electrodes and a portable voltammetric analyzer.

Materials and methods

The work uses native and modified carbon-containing screen-printed electrodes (SPCE), potentiostat-galvanostat R-40X (RF, Chernogolovka), as well as a portable analyzer AK-1 (Rusens LLC, Moscow).

The object of the study was model solutions containing heavy metals and water of the Zaravshan river (Samarkand region).

Results and their discussion

Figures 1-2 show the appearance of the portable analyzer AK-1 and the potentiostat-galvanostat P-40X with the module FRA-24, and Figure 3-8 voltammograms obtained on native and modified screen-printed electrodes in model solutions containing individual and mixed heavy metal ions, indicating the type of electrode and the method of removing the VA curves.

Figure 1. Portable analyzer AK-1.                  Figure 2. Potentiostat-galvanostat P-40X

Laboratory studies have shown an adequate response of screen-printed electrodes modified with a thin film of mercury, bismuth, gold to the presence of corresponding ions of copper (II), cadmium (II), lead (II), iron (III) in solutions. bismuth (III), chromium (VI) and the possibility of using such a technique of voltammetric analysis of these ions in real objects by the additive method.

Table 1. shows the results of single measurements of heavy metal ions in the waters of the Zeravshan River, conducted in the field, directly at the sampling site.

Table 1.

Results of measuring the content of heavy metal ions in the Zarafshan river, conducted in the field

As can be seen from the results obtained, the content of lead, cadmium, chromium, and arsenic ions in the water of the Zeravshan River exceeds the MPC for drinking water, which requires certain efforts and funds to condition the source water for supply to the water supply network to consumers [9].

Thus, measurement in the field, on the one hand, provides faster data collection, and on the other hand, it prevents the results from being influenced by chemical changes that occur after sampling, for example, the oxidation of arsenic (III) to arsenic (V). An analytical platform based on a portable voltammetric analyzer and modified screen-printed electrodes and software that requires almost no complex maintenance can meet all the requirements for measurements in the field, i.e. on-line and in situ analyses.

Additional Information

The work was submitted to the competition "The Best Young Scientist-2022", organized as part of an international project with the support of the Association of Legal Entities in the form of the association " Nationwide Movement Bobek " (Kazakhstan, Nur-Sultan).

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