Chemosensors 2022, 10, 413. https://doi.org/10.3390/chemosensors10100413 www.mdpi.com/journal/chemosensors Article Low-Tech Test for Mercury Detection: A New Option for Water Quality Assessment Nadezhda S. Komova, Kseniya V. Serebrennikova, Anna N. Berlina *, Anatoly V. Zherdev and Boris B. Dzantiev A.N. Bach Institute of Biochemistry, Research Center of Biotechnology of the Russian Academy of Sciences, Leninsky prospect 33, 119071 Moscow, Russia * Correspondence: anberlina@yandex.ru Abstract: Mercury pollution is a global environmental problem, especially in low-resource areas where artisanal iron mining is taking place and industrialization is on the rise. Therefore, there is a demand for simple methods for the determination of toxic metals at low. In this study, an on-field membrane lateral flow test system for sensitive and specific detection of Hg 2+ in natural waters ma- trix is proposed. For this purpose, mercaptosuccinic acid (MSA) conjugated with protein-carrier (bovine serum albumin) was pre-impregnated in the test zone of the strip and used as a capping agent for mercury complexation. Quantitative evaluation of the analyte was provided by the use of gold nanoparticles stabilized with Tween-20 as a detecting agent. The sensing principle relies on the formation of Au–Hg nanoalloy during the migration of a solution containing Hg 2+ along the strip, followed by capture in the test zone with the formation of a colored complex. Under optimum con- ditions, the proposed lateral flow test exhibited the linear correlation between color intensity in the test zone from the concentration of Hg 2+ in the range of 0.04–25 ng/mL. The total analysis time was 11 min, without the need for the usage of additional instrumentation. The detection limit was esti- mated to be 0.13 ng/mL, which is 45 times lower than the WHO guidelines. The applicability of the proposed lateral flow test was confirmed by the analysis of natural waters, with the recoveries rang- ing from 70 to 120%. Due to the high affinity of Au to Hg and the use of a capping agent for mercury complexing, the developed system demonstrates high selectivity toward Hg 2+ . Compared to exist- ing analytical methods, the proposed approach can be easily implemented and is characterized by economy and high analytical performance. Keywords: mercury detection; mercaptosuccinic acid; gold nanoparticles; lateral flow test; out-of-lab analysis; environmental monitoring 1. Introduction To date, mercury pollution forms an important subject of environmental concern [1,2]. The risk of contamination results from the widespread use of mercury in industrial processes, as well as its physicochemical properties associated with high volatility, sorp- tion capacity in the soil, and solubility of mercury vapor in precipitation. Excess intake of mercury compounds in the human body leads to dysfunction of the nervous, digestive, and immune systems, as well as damage to the lungs and kidneys. [3]. Due to the high toxicity of mercury, permissible levels of its safe content in environmental objects have been established. The permissible level of Hg 2+ in drinking water varies from 0.5 ng/mL to 6 ng/mL according to the recommendations of organizations in various countries (USA [4], Canada, China, Russia [5]), and the WHO [6]. Such requirements are met by highly sensitive analytical techniques including chromatographic methods (gas chromatog- raphy, liquid chromatography), capillary electrophoresis, and spectroscopic methods (atomic absorption, inductively coupled plasma mass spectrometry, and cold vapor atomic absorption), which are described in detail in review articles [7,8]. Citation: Komova, N.S.; Serebrennikova, K.V.; Berlina, A.N.; Zherdev, A.V.; Dzantiev, B.B. Low-Tech Test for Mercury Detection: A New Option for Water Quality Assessment. Chemosensors 2022, 10, 413. https://doi.org/10.3390/ chemosensors10100413 Academic Editor: Kien Wen Sun Received: 8 September 2022 Accepted: 10 October 2022 Published: 11 October 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (https://cre- ativecommons.org/licenses/by/4.0/).