Currently, there are commercial colorimetric devices on the market used for the semi-quantitative determination of various individual analytical parameters. They are fast, low-cost systems that can be used by non-specialized personnel and that allow for easy ‘in situ’ analyses, without the need to transport the samples to central laboratories. However, this type of commercial kits can result in analyte losses, which affects the accuracy and precision of the method and poses a risk, due to exposure to the vapors generated, in addition to having limited sensitivity, which translates into the inability to determine low concentrations of analyte. “This factor is especially relevant when it comes to determining analytes whose maximum permitted limits (above which significant risks to the environment and/or human health occur) are very low”, explains the teacher and researcher from the QA2 group, Analytical and Food Chemistry, and the Marine Research Center of the University of Vigo Francisco Javier Pena. With the aim of providing solutions to the limitations of colorimetric kits marketed on the international market, the QA2 group has developed a device that allows, in combination with available image digitization and processing systems, the determination of a wide variety of volatile or non-volatile contaminants, such as arsenic, mercury, ammonium, bromide, free chlorine, sulfite, sulfide or cyanide, through the formation of a volatile form of the analyte.
“The device, which allows the determination, both qualitative and quantitative, of analytes of interest present at low concentrations in a fast and safe way, could be an attractive alternative for the in situ analysis of pollutants in sectors such as the environment and food”, explains Pena. The device, which obtained the grant of the patent requested by the research group from the Spanish Patent and Trademark Office, is considered by its authors to be of interest to companies and organizations dedicated to environmental control, where the cost reduction and simplicity of the device could offer an alternative system to the measurements carried out in central laboratories.
Very fast analysis time, depending on the system involved
The device, on which the research group began working in 2016, allows for obtaining both qualitative (identifying the presence or absence of the contaminant) and quantitative (determining the concentration of the contaminant) information. “The analysis time is very fast, although it will depend on the system involved. In the case of the method to determine arsenic in water, it is possible to quantify said contaminant at concentration levels below 10 ng/mL (maximum limit allowed in drinking water) in just five minutes. But the analysis time can be even shorter when it comes to determining analytes at higher concentration levels,” explains the teacher and researcher.
A colorimetric analysis method for the determination of arsenic in water
In addition to the patent, the QA2 research group has developed a non-instrumental and miniaturized colorimetric analysis method for the determination of arsenic in water. The method, which was published in the journal Analytica Chimica Acta (2018) as a Feature article, allows the determination of both total inorganic arsenic and arsenic (III) in water at very low concentration levels quickly, easily and without the need to use analytical instrumentation. “The presence of arsenic in natural waters is a serious environmental problem and prolonged exposure to this pollutant through the consumption of water and food can cause cancer and skin lesions and is also associated with developmental problems, cardiovascular diseases, neurotoxicity and diabetes”, details Francisco Pena, who recalls that organizations such as the World Health Organization or the United States Environmental Protection Agency have established a maximum permitted concentration of 10 ng/mL in drinking water.
Compared to other non-instrumental methods and colorimetric kits, and unlike many of them, the one developed by the research group at the University of Vigo allows the determination of arsenic at concentration levels lower than the maximum concentration limits allowed in drinking water. “In addition, this method can be used as a screening method in a complementary way to instrumental analysis methods, which allows rapid decision-making and a significant reduction in the number of samples to be analyzed using instrumental analysis methods,” explains Pena.
The research activity of the QA2 research group is co-financed by the FEDER/FSE Galicia 2014-2020 Operational Program.
Source: DUVI
