Expedition from analytical to the electrochemical sensor: A review of the measurement techniques of Arsenic in water

Amit Awasthi; Vajinder Kumar; Kushagra Rajendra; Sumanta Das; Ankush D Swarkar; Rajeev Kumar Gupta; Balendu Shekher Giri

doi:10.4491/eer.2025.085

Environ Eng Res > Volume 31(1); 2026 > Article

Awasthi, Kumar, Rajendra, Das, Swarkar, Gupta, and Giri: Expedition from analytical to the electrochemical sensor: A review of the measurement techniques of Arsenic in water

Review

Environmental Engineering Research 2026; 31(1): 250085.

Published online: May 8, 2025

DOI: https://doi.org/10.4491/eer.2025.085

Expedition from analytical to the electrochemical sensor: A review of the measurement techniques of Arsenic in water

Amit Awasthi^1,^†

, Vajinder Kumar², Kushagra Rajendra³, Sumanta Das⁴, Ankush D Swarkar⁵, Rajeev Kumar Gupta¹, Balendu Shekher Giri⁶

¹Department of Applied Science, UPES, Dehradun 248007, Uttarakhand, India

²School of Chemistry, University of Leeds, Leeds, United Kingdom

³Amity School of Earth and Environmental sciences, Amity University Haryana, Manesar, Pachgaon, 122412, Haryana, India

⁴Ramakrishna Mission Vivekananda Educational and Research Institute, Howrah, West Bengal, India

⁵Department of Information Technology, Shri Guru Gobind Singhji Institute of Engineering and Technology, Nanded, Maharashtra, 431606, India

⁶Sustainability Cluster, School of Engineering, UPES, Dehradun, 248007, India

^†Corresponding author: E-mail: awsthitiet@gmail.com, Tel: +917060105155, ORCID: 0000-0001-8811-2338

Received February 11, 2025 Revised May 1, 2025 Accepted May 7, 2025

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Arsenic, the tenth most prevalent element in the Earth’s crust, is known for its high toxicity and carcinogenic potential. Because of serious health risks associated with even low concentrations of arsenic in drinking water, the development of sensitive, accurate, and reliable detection methods is of critical importance. Hence, in the present review, comparative analysis of analytical lab and portable chemical methods of determination of water in arsenic are conducted, focusing on their accuracy, precision, detection limits, and practical applicability. The results demonstrate that analytical methods provide high accuracy and precision, while commercially available portable kits offer convenience and rapid results. Electrochemical sensors, particularly those modified with nanomaterials and other functional materials, show potential for on-site detection, with detection limits as low as 1 ppb. The electrode modifier, graphene oxide-gold nanoparticles composite, enhances the sensor’s sensitivity and selectivity towards detection. Without disapproving any of the measurement techniques, the review offers appropriate details for the assortment of several techniques for the measurement of arsenic, and there are important challenges in arsenic detection. Hence, this review opens a scope for those working in this critical area of arsenic determination and its advancement with minimal cost and less risk to health and the environment.

Keywords: Analytical technique, Arsenic, Electrochemical, Gutzeit, Nanoparticles, Sensor

Graphical Abstract

Keywords: Analytical technique, Arsenic, Electrochemical, Gutzeit, Nanoparticles, Sensor

1. Introduction

Arsenic is the 20^th most abundant mineral in the earth’s crust and the 12^th most abundant mineral in the human body and is widely distributed throughout the environment in the air, water, and land [1]. Arsenic belongs to the group of metals which is called metalloids. A metalloid is a chemical element that shows the properties of metal and nonmetals. The toxicity of arsenic depends upon its existence i/e., whether it is in inorganic or organic form (Fig. 1). Research indicates that arsenic is most frequently found in natural water as inorganic oxyanions with the oxidation states +3 and +5, respectively [2–4]. Due to their extreme toxicity and cancer-causing potential, pentavalent arsenate (As⁵⁺) and trivalent arsenite (As³⁺) are two prevalent forms of inorganic arsenic that can have a detrimental effect on the environment and eventually accumulate in the body through the food chain. As(III) is 60 times more toxic than As(V) [5]. Considering that arsenic compounds are hazardous and carcinogenic, the international agency the Food Drug Administration (FDA), World Health Organization (WHO), and the United States Environmental Protection Agency (USEPA) define the permissible limit of arsenic for drinking water at 10μg/L [6]. The threshold level for arsenic is still found to be more than 50 μg/L in some parts of nations, such as India, Pakistan, China, Bangladesh, and Taiwan due to which more than 45 million people belonging to developing countries of Asia are exposed to 50 μg/L of arsenic [7–10].

People are exposed to large amounts of inorganic arsenic by eating contaminated food, drinking contaminated water, and utilizing contaminated water for crop irrigation and food preparation [11–13]. Ground water is one of the important sources of drinking water along with the other sources like natural rain, rivers and glaciers, etc. [14]. Arsenic contamination in water is of concern because it enters both through natural reasons (such as weathering of parent material, volcanic eruptions, and geothermal waters) and anthropogenic reasons (such as agricultural pesticides and herbicides, paints, fungicides, insecticides, manufacture of semiconductors, light emitting diodes, and components of lasers and microwave circuits) [15]. Inorganic arsenic species are toxic and generally available in groundwater with higher concentrations in comparison to those recommended by the WHO [16]. The water becomes contaminated underground by rocks that release arsenic

Arsenic exposure occurs from inhalation and absorption through the skin [17]. Drinking arsenic-contaminated water causes different types of multisystem diseases. Most of the arsenic that is consumed and breathed is absorbed into the bloodstream through the digestive system and lungs. The gastrointestinal system absorbs over 95% of the trivalent arsenic that is ingested. It is dispersed across several different organs, including the skin, liver, kidney, and lungs [18] The health effects of Arsenic consumption vary from skin scratches to kidney, liver, and brain cancers, along with stomach poisoning [8,9]. According to a rough estimate, arsenic poisoning has afflicted more than 100 million individuals [19,20].

Before designing the removal strategies of Arsenic, detection of Arsenic is very important, so that early detection will stop toxic exposure and give chance to timely mediation to protect health. Many techniques are available for arsenic detection which include the lab to-location and analytical to-sensing methods. In the present manuscript, before discussing in detail about the detection of arsenic in water, its separation/extraction is discussed briefly for its basic understanding. After the brief introduction to the separation and extraction process, various types of techniques along with their advantages and disadvantages, and then the necessity for and advancement in the sensor techniques will be discussed systematically in detail.

2. Extraction/Separation of Arsenic

Understanding the different extraction procedures is important before discussing the journey of measurement of Arsenic in water from analytical to portable commercially available kit based on the Gutzeit chemical reaction. Hence, Fig. 2 is designed that gives a brief background on the different separation techniques, as it would help to set the point before diving into the main discussion on the measurement of arsenic in water. Fig. 2 represents the important procedures for separation/extraction of Arsenic like Solid phase extraction, Hydride, generation, Liquid-liquid extraction, Liquid chromatography, Capillary electrophoresis [21–25]. As per the requirement, these different techniques are used for the extraction and separation of Arsenic from samples. All techniques have some advantages or disadvantages, so as per the nature of Arsenic analysis, a particular method is used for separation. For more details related to the procedure of arsenic extraction/separation, please follow Chen et. al. [26].

3. Detection Techniques to Measure Arsenic

Arsenic occurs in different oxidation states and forms different species whose toxicological and chemical properties differ. Speciation of Arsenic is important before its detection and classified into two approaches. In the first approach, certain species of arsenic are collected using a highly selective extraction/detection technique. The other includes keeping together a number of species of Arsenic that are interesting and then separated with a well-matched technique before detection. For the detection of Arsenic with the appropriate methods, necessary technical and economic criteria are required like reliability, sensitivity, selectivity, operating range, properly trained personnel, cost, etc. Keep these criteria in mind, different techniques are used to detect arsenic. In the coming section, analytical, portable chemical methods are discussed to understand their advantages and disadvantages.

3.1. Analytical Methods

An analytical method is also called a lab method in which samples are collected from the location to the lab for analysis or determination of metal. In the spectrometric analytical method, the Arsenic compound is converted to the Arsine compound. Arsine gas is then used to detect Arsenic through the spectroscopy technique. Atomic absorption, atomic emission, and mass spectrometry are the three commonly recognized analytical technologies based on atomic spectroscopy. Spectrometric techniques like Atomic Absorption Spectroscopy (AAS), Mass spectroscopy (MS), and Atomic Fluorescence Technique (AFS) are the most favorable techniques used by the researcher and technician for the validation and calibration of other arsenic detection methods.

3.1.1. Atomic absorption spectroscopy

AAS is an analytical technique that is used to detect certain elements in a sample, based on the principle that atoms or ions may absorb light with a certain, distinct wavelength. Individual elements will absorb wavelengths differently, and these absorbances are measured against standards. Relation between the absorption of energy and the analyte’s (element of interest) concentration is used to detect the concentration of the unknown sample by interpolation of standard values [27]. Based on the sample introduction, there are two modes, Flame Atomic Absorption Spectroscopy (FAAS) and Graphite Furnace Atomic Absorption Spectroscopy (FAAS) which work on the sample principle for the detection of Arsenic. In FAAS, the sample is introduced as an aerosol into the flame whereas in GFAAS the sample is introduced directly into a graphite tube. Comparatively, FAAS is preferred where a better detection limit is required, and a small sample is available. By using the principle of spectrometry, Arsenic was detected first time using AAS in 1980 [28]. Due to high selectivity, sensitivity, and low detection limits, AAS is often attached to Hydride generation (Hg) for better results [29]. Due to loss cost, Hg-AAS show more benefits than ICP-MS.

3.1.2. Inductively coupled plasma optical emission spectroscopy

In the early 1960s, the Inductively Coupled Plasma (ICP) technique was first introduced. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) is a technique in which the measurement of elements like Arsenic in water can be determined by analyzing the emitted light due to the introduction of the sample into an ICP. The sample is ionized, atomized, and energized, during its entry into the ICP, and energy is released when the electrons return to the stable ground state. This energy emission in the form of light is passed through a spectrometer where it is further analyzed, identify, and quantify for the elemental concentration [30]. The use of ICP-OES is more complicated in comparison to atomic absorption techniques, but it gives better results in terms of sensitivity. Moreover, Monochromatic light is not required for the ICP-OES technique, so it is preferred in comparison to AA where synchronous assess is for all elements is required. Because of the good detection limit, excellent precision, Excellent LDR, and use of inert gas, it is preferred for routine measurement in comparison to AA.

3.1.3. Inductively coupled plasma mass spectroscopy

In Inductively coupled plasma mass spectroscopy (ICP-MS), when a sample is atomized, ionized, and energized during its movement in ICP, the charged ions enter the mass spectrometer. In MS, ions are split according to their mass before reaching the detectors. This means in ICP-MS elements detection in the sample is based on their masses not only on the emission of energy of a particular wavelength [30]. This method of detection produces substantial advancement in sensitivity even more than ICP-OES. ICP-MS technique has the advantage of extremely low detection limit, large linear range, and the possibility to detect isotope composition of elements. In terms of the type of measurement and detection technology utilized, ICP-MS and ICP-OES are different. The main drawback is the high cost and occurrence of spectral and non-spectral interferences during detection [31].

3.1.4. Atomic fluorescence spectroscopy

Atomic fluorescence spectroscopy (AFS) is one of the important spectrometry analytical methods used to determine the concentration of elements in samples by converting samples into gaseous atoms. This method comprises the light source that excites the gaseous atoms to a higher energy level trailed by a deactivation that involves the emission of a photon. This emission process provides the measured fluorescence signal [32]. AFS is different from AAS and AES as it involves both radiative excitation and de-excitation. It is simpler than AAS and selected better than AAS and is almost similar to ICP-MS with low running cost. AFS was first used with HG in 1990. One of the key features of this technique is its essential high sensitivity. All the analytical lab techniques, no doubt have many advantages like good selection and sensitivity, but it is expensive, time-consuming, and requires well-trained persons for the detection of arsenic. So, there is a need for some other method that consumes less time and money and is easily accessible. To save time, a portable kit was designed to analyze the water sample for Arsenic detection.

4. Portable or Chemical Methods

Different discussed laboratory analytical methods used for the detection of arsenic have some drawbacks due to their expensive nature and sophisticated instrumentation. Moreover, these methods have complicated sample preparation processes that consume a lot of time due to which they are not acceptable for routine real-time measurement. Because if the samples are not stored properly then some arsenic gases evaporate and produce wrong results. So, in place of sophisticated instrumental analytical techniques, several chemical methods and portable test kits were designed. One of the earlier commercial field kits is based on the Gutzeit reaction [33] and is one of the excellent alternatives to the lab methods that provide an acceptable limit of detection, fast response rate, and cost per sample. Working on these kits is based on Gutzeit reaction that involves mainly two steps. Firstly, arsenic impurity is converted into arsenious acid by reducing agents like Zinc, etc. Further, arsenic acid is reduced to arsine gas by reacting with nascent hydrogen. After that, arsine gas reacts with mercuric bromide paper and produces a color change in the paper (Fig. 3). The Yellowish color of the paper depends on the number of −AsH₂ groups bound to the mercury. These field kits give semi-quantitative results, as the paper color matched with a standard color chart of arsenic concentration. This change in color from white to yellow is matched with a standardized color scale or digital readout.

It is observed that the results of these field kits were misleading and produced false negative and false positive results because visual perception of yellow color varies from person to person, so the results are not reliable [34,35]. Results produce in these methods are semi-quantitative and qualitative as the detection is based on the color chart [36–38]. It is also quoted in the study hat 50% of arsine gas is evaporated during analysis which also poses a serious concern about the health of the concern, which is in close contact during analysis, as arsine gas is more harmful in comparison to arsenic in solutions. Similar to the Gutzeit method, tthe Ag-DEDTC method also produced hypertoxic AsH₃ gas which shows a significant negative effect on the environment and operators. Merck kit based on the Gutzheit method was used in Bangladesh for the routine measurement of arsenic in water with a poor detection level of 0.1 mg/L. One similar type of method is called the Hach method in which Sulphamic acid is replaced by HCL [39]. The molybdenum blue method is one of the simple chemical methods which is suitable to measure the AS(V) directly and AS(III) indirectly by calculating the difference between total AS and AS(V). In these types of methods, an arsenic determination is done by spectrophotometry of arsenomolybdic acid reduced to molybdenum blue [40]. This method is fast, simple, and cost-effective but it is considered unoptimized [41]. Mostly these methods require mercuric salt as a color-generating regent which has health and environmental risks if not handled properly. The process and regent may change but the main idea is the reduction of arsenite and arsenate with Zinc into arsine gas. This Arsine gas as a by-product is toxic in nature and is one of the major drawbacks of these types of test kits. Hence, there is a need for certain potential mitigation strategies for the portable arsenic test kit especially based on the Gutzeit method like to reduce the effect of arsine gas release during the measurement of arsenic in water are 1) Use of arsine gas absorber or traps to neutralize arsine gas before it released to the environment. 2) Improved ventilation & outdoor testing to reduce inhalation risks. 3) Use of personnel protective equipment (PPE) including masks with gas filter, safety goggles and globes, etc. 4) Proper testing and follow safety protocols if exposure occurs. Along with these mitigation strategies, there are some alternative safer approaches including 1) calorimetric test strips based on thiol or Gold nanoparticles (NPs) methods that measure arsenic without producing arsenic gas. 2) Electrochemical sensors which are modified with carbon NPs, gold NPs, metal oxide, etc. without generating arsenic gas. 3) Photometric portable device based on the color intensity measurement with sensors without emission of any harmful gas. 4) Compact microfluidic system that incorporates onto chips without generation of arsenic or toxic gas.

Table 1 summarizes the performance metric of different measurement techniques of arsenic in water. Based on the comparison shown in Table 1, it is observed that available commercial kit is less sensitive in comparison to the lab analytical methods and in general LOD values of Lab techniques like AAS, AFS, etc., have lower values in comparison to the available commercial kit in the market. It is also observed that practical values of LOD in the case of commercial kit is found to be higher in comparison to theoretical values. Based on these performance values of commercial portable kit and analytical methods, Fig. 4 is designed that shows the comparison in terms of benefits and limitations during the measurement of arsenic in water.

5. Disadvantages of Analytical and Chemical Methods

Both Analytical and portable methods, especially based on the Gutzeit chemical reactions, have some disadvantages along with advantages that need to be addressed for better determination of arsenic as shown in Fig. 4. Analytical methods have high sensitivity and low limit of detection whereas portable chemical kit methods are less expensive and fast responsive in comparison to analytical methods but the major disadvantage of having environmental and health risks. So, there is a need for alternate techniques that fulfill the following criteria: a) must be selective and sensitive, b) stable enough for the field use and handy to use, c) Fast and produce repeatable results, d) less expensive and easy to implement e) minimum or no health and environmental risk, e) easy to use i.e., minimal training required. Electroanalytical techniques are a viable replacement for traditional methods in both qualitative and quantitative analysis.

In Fig. 4, Portable kit represents the commercially available kit based on the Gutzeit chemical reaction. Available commercial kit which are used for measurement of arsenic in water has quoted low theoretical LOD values up to 10 ppb but practical value is more than these theoretical values and limited accuracy in the measurement is observed below 20 ppb (Table 1). Researchers are working to reduce the LOD [48,49] and one of the recent developments in this area is by Ravula et al., where they designed sensitive digital point of care test (POCT) kit that detect the Arsenic in water from the range 4 to 100 ug/l with response time of 3 to 5mn [50]. This paper-based optical green sensor kit, once commercially available, has the potential to be a significant breakthrough in the development of portable detection systems, particularly in terms of sensitivity and long-term usability.

To fulfill the gaps or disadvantages observed in these techniques (Analytical and commercially available kit), the researchers used the concept of the sensor for the determination of arsenic in water efficiently everywhere with the hope of more advancement in terms of sensitivity, selectivity, cost, eco-friendly, etc. Because the drawbacks of laboratory-based approaches include sample preparation that is time-consuming, expensive, labor-intensive, and requires discrete data compilation. The electrochemical sensor approach provides the option of on-site testing outside of a laboratory which is affordable, easy to fabricate, sensitive and analyzes data more quickly and efficiently with less trained personnel. In the coming section, the electrochemical sensing technique along with the modification of their electrodes are discussed.

6. Electrochemical Sensors

Electrochemical sensors are a class of chemical sensors in which the electrode is the transducer element that detects or sense signals from its surroundings and transforms them into a significant or scientific signal. The basic idea behind the detection of analytes by electrochemical sensors requires the measurement of electric current produced by electrochemical reactions in the electrochemical system. Three essential components of the electrochemical sensor are the analyte or sample, a receptor that binds/recognizes the sample, transducer that converts the primary signal into a current signal. Fig. 5 represents the sketch for the process of the electrochemical sensor. From the left, the first component is an analyte or sample of water that contains arsenic species. After the analyte, there is a receptor that binds the sample and is recognized by the recognition element. The primary signal produced during the recognition process is converted by the transducer into an electrical signal. After that, the signal is amplified, processed, and then displayed on the screen of a mobile, laptop, etc. Voltammetry, potentiometry, amperometry, and conductometry are important methods employed in electrochemical sensing. In general, electrochemical sensors consist of three electrodes: reference, working, and counter electrode. No doubt, in comparison to analytical and chemical techniques, electrochemical techniques have some advantages but still, a lot of work is going on to make them smarter by increasing their response time, sensitivity, etc. Nanoparticles (NPs) play a crucial role in smart electrochemical sensors due to their unique physical, chemical and electrical properties, particularly their high surface area, which enhances sensor performance and sensitivity [52,53]. Generally, the working electrode of electrochemical sensors is modified with the help of different types of NPs that improve the selectivity, sensitivity, and stability of the sensors. Due to the improvement in specific surface area and associated surface free energy, the electrodes treated with nanomaterials considerably enhanced sensitivity when employed for the electrochemical detection of heavy metals [54]. The NP-modified electrodes have notable benefits over standard macro electrodes in terms of improved mass transfer, decreased solution resistance, low detection limit, and superior signal-to-noise ratio. They may also be created as random arrays of microelectrodes. In the coming section, different types of NPs are discussed briefly intending to understand the basic role of NPs in the modification of electrochemical sensors.

Numerous kinds of nanomaterials (Fig. 6) are used to modify the electrodes to improve the electrochemical sensing of arsenic including carbon nanoparticles (NPs), noble metal NPs, bimetallic NP and metal oxide NPs, Metal oxide NPs, etc. [55–60]. An overview of various NPs used for electrode modification is presented in Supplementary Fig. S1.

6.1. Carbon Nanoparticles (CNPs)

Their special features concerning the optical, electrical, thermal, and mechanical properties help CNPs to advance the electrodes’ performance in electrochemical transmitting [51]. A few commonly used nanostructured carbon materials are:

6.1.1. Carbon nanotube (CNTs)

In 1991, CNT was invented by Sumio Iijima comprising 1D cylindrical tubes. They are unique because of the strong intermolecular bonds between alternating hexagonal rings that result in an accumulated structure. CNTs can have different numbers of layers, thicknesses, and even different lengths, and their diameter is in the nanometer range and length varies from several millimeters to centimeters [59]. CNTs have good support structures because of their high surface area and conductivity and can be used for electrical applications by immobilizing other organic and metallic chemical species. In addition, CNT electrodes benefit from faster electron transport kinetics than bulk carbon electrodes.

6.1.2. Graphene

In 2004, graphene was discovered by Novoselov and others. Graphene is one of the thinnest and strongest materials. It is considered a basic building material for other carbon nanomaterials. Stacking produces 3D graphite, rolling produces 1D CNTs, and wrapping produces 0D fullerenes 1958 [60, 61]. A commonly used method to form Graphene Oxide (GO) is the Hummer method, which includes adding potassium permanganate to sulfuric acid, graphite, and sodium nitrate solutions. Graphene-based posites have proven to be efficient materials for detecting low concentrations of arsenic with excellent selectivity, sensitivity, and reproducibility [62]. Composite composition and temperature play an important role in the conductivity of deposited films by the nanocomposites [53].

6.2 Metal Oxide NP

Other types of NPs are metal oxide particles. It includes Fe₃O₄, SnO₂, TiO₂, etc., (Fig. S1) and every metal oxide has an advantage over others for the detection and reduction of arsenic. Metal oxides of ferrite have good absorption properties along with great paramagnetism properties [63]. Reduction of As (III) can be achieved with the help of Fe (III) and Fe (II). Fe₃O₄ and Fe₂O₄ NPs modified electrodes can be used to remove arsenic from H₂O because of their high absorption properties and super-paramagnetism [64]. Manganese oxide (MnO_x) is useful for As(III) detection in alkaline media. It is applied to real water samples like tap water and bore well [65]. Cobalt oxide (CoO_x) NPs modified electrodes have great catalytic activity toward the oxidation of arsenic (pH range 5–11) [66]. Tin oxide (SnO₂) nanosheets are made along with the surface modified with Au. The thin nanosheets of SnO₂ provide stronger absorption and improve the detection of As (III). Titanium oxide (TiO₂₎ provides 3D porous structure for the determination of As (III) in the blood sample, because of its great surface area and good electron transfer properties [67]. Cadmium Oxide (CdO) NPs are generally doped with fluorine and then this film is developed for arsenic detection and can be operated over a broader potential range [68]. Whereas IrO₂ NPs modified electrodes used oxidation for the detection of arsenic, and work on low potential and a wide range of pH [69]. Ruthenium Oxide (RuO) NPs modified electrodes are used as a determination of arsenic, but the use of platinum can increase active sites for the oxidation of arsenic [70]. Thallium oxide (ThO₂) provides good sensitivity and helps in the detection of arsenic in fresh water, and coal fly ash [71]. So basically, Metal oxide NPs modified electrodes used the redox reaction (Oxidation and reduction) for the electrochemical detection of As (III) with good sensitivity and selectivity.

6.3. Noble Metal NP-Modified Electrode: Gold and other metals

Noble metals are the metallic element that has certain properties like resistance to corrosion as they don’t react with oxygen and are found in their raw form in nature like gold, platinum, ruthenium, iridium, etc. Noble metal NPs have drawn great attention in the detection of heavy metals due to their high surface area, excellent catalytic activity, and electrical conductivity. These metal NPs reduce the overpotential of the electroanalytical reaction while maintaining the reversibility of the redox reaction. Additionally, the noble NPs can be readily electrodeposited onto the working electrode which makes them more efficient and easier to use compared to other NPs. Now, these noble metals are widely used in the making of the noble metal NPs-modified electrode [72,73]. Gold (Au) NPs deposited by using step methods with the glassy carbon electrodes are used for the detection of As(III) which is better than that of a macro Au electrode [74]. Au NPs deposited by using the DPSAV technique with boron-doped diamond electrodes detect the arsenic in real water as well can be applied for the detection of inorganic arsenic and gold deposited on electrodes formed to be uniform where the density of the particle is 10-9 cm⁻² [75]. Au nanocomposite electrode is efficient to detect As(III) at any pH whereas it detects As(v) at around pH(1) [76]. Au nanoparticle-modified screen-printed electrodes in L-lactide are used to stabilize Au nanoparticles of an average size of 10 nm and reported for detection of As(III) that avoids interference of metals like Copper (Cu), Cadmium (Cd), Iron (Fe), Manganese (Mn), Nickel (Ni), or Zinc (Zn) [77]. Silver (Ag) NP-modified electrode helps in the detection and removal of inorganic arsenic (III) from contaminated water with help of diffusion by a membrane, it is a 3D network that shows great absorption properties [78]. Ruthenium (Ru) NPs modified electrodes detect As(III) in water and the advantage of this method is that there is no need to look for parameters like pre-concentration potential, stirring, time, etc. Iridium (Ir) NPs modified electrodes detect As(III) in tap water by a flow method injection coupled amperometry that are free from cations and anions which are present in water samples [79]. Whereas Zirconia (Zr) NP-modified electrode detects As(III) in the environment at pH(7) and is used to check As(III) ions in various samples like water, food, and some environmental samples to get rid of toxic solutions [80].

6.4. Bimetallic NP-Modified Electrodes

Bimetallic NPs have great sensing properties, conductivity, and catalytic activity. They have a 3D network that is porous for the electron transfer process thus improving sensitivity and selectivity. Gold and copper NPs are used for the determination of As(III) and proposed by the hydrothermal method and it also showed better electrochemical performance at ppb levels and detects lower limits than Au electrode [81,82].

6.5. Nano Biomolecule-Modified Electrodes

Another important way to modify the electrodes is with the use of nano biomolecules. DNA-Au NPs, Arsenite oxidase–CNT NPs, and aptamer self-assembled on-screen printed modified electrodes are the common example in which deposition or modification are done by the biomolecule which reduces the size of the electrochemical sensor effectively. To understand, take one example of DNA-Au NP-modified electrodes in which biosensor modifications are done with DNA for heavy metal detection [60]. The As(III) biosensor interacts with calf thymus DNA (both DNA double as well as single). Interactions between As(III) and guanine imply the potential ability for indirect determination of arsenic [83]. Aptamer type of sensor is one of the important types of determination techniques in which a lot of work is going on because of its remarkable properties [84,85].

Table 2 compares the LOD performance for arsenic measurement in water of different electrode, electrochemical techniques modified with different NPs, Bimetallic material, metal oxide, CNTs, etc. Overall, it is observed that the electrode modifier can significantly decrease the LOD values and nanomaterials, and composite modifiers significantly enhance sensor sensitivity, with GCE being the most used electrode base. Among the tested material Metal oxide like Fe₃ O₄/ionic liquids on GCE demonstrated the lowest LOD at 0.0008 ppb [93], indicating exceptional sensitivity. Gold nanoparticles (Au NPs) and Bimetallic combinations (Au-Cu, Au-Pd, Au-Pt) offered good detection limits, highlighting their potential for real-world applications. No doubt, Electrochemical sensors modified nanomaterials, oxide, nanoparticles enhance the detection limit, sensor’s sensitivity and selectivity toward arsenic detection. Still there but artificial intelligence (AI) is one of the important emerging tools which play an important role now a days in the field of environmental parameters measurement like air pollution [96,97], water and metrological parameters [98,99]. Hence, Future integration of AI with electrochemical sensors is expected to revolutionize arsenic detection in water, enabling real-time monitoring, predictive analytics, and enhanced accuracy through machine learning algorithms.

7. Distinctiveness of Current Study

Table 3 represents the summary of different reviews extracted from ScienceDirect with the keywords “arsenic and sensors” in the title for the last 5 years from 2018 to 2025. There are a total of 40 articles out of which six are review articles and the remaining 34 are research articles extracted based on the above-mentioned search criteria. In 2019, Devi et al., also summarized the review article up to 2019 on arsenic detection [106]. The reviews shown in Table 1 and summarized by Devi et al. mainly focus on 1) one of the measuring approaches like analytical, portable, etc.,2) the type of sensor either nano-sensor, biosensors [100,101,103], aptamer sensors [104], electrochemical sensors [101,102], optical sensors [106], etc. or 3) advancement in the doped material on the sensor’s electrodes like CNPs, Metaloxide-NPs, Nano-biomolecule, etc. [106]. However, there is no single review that critically discussed the journey of the different types of measurement techniques of arsenic in water. The current review critically discussed the journey of arsenic measurement along with the drawbacks and advantages of different techniques. The distinguishing feature of the present manuscript is that it does not focus on the review of a single approach/technique or type of sensor, but efforts are made to club the information about the different types of detection techniques, and their application as per the requirement of detection without disapproving of any technique.

8. Conclusion and Future Perspectives

The review has systematically discussed and summarized the journey of different techniques from laboratory to smart portable sensor methods for the determination of arsenic in water. Laboratory techniques like AFS, ICP-MS, HG-AAS, etc, can access arsenic levels lower than 10 μg/L. But these highly sensitive techniques are costly, huge and require training for processing and maintenance. Hence, the analytical lab method is not advised where routine measurements and/or near real-time measurements are required. Whereas portable commercially available test kit determination is not expensive but often produces false positive and false negative results, thus unreliable for arsenic determination below 70 μg/L. Moreover, the reaction that occurred in these field kits produces arsine gas which is toxic and hazardous to the user and environment, and hence not environment friendly. For calibration purposes analytical techniques like AAS, GFAAS, etc are preferable. Whereas if routine semi-qualitative or qualitative estimation of arsenic is required then kit-based methods are preferred. These facts highlight the need of better techniques for the measurement of arsenic which are sensitive, economical, and have minimal effect on health and the environment. Electrochemical sensors for the determination of arsenic are promising alternatives in terms of cost, LOD, response time, health, and environmental risk. In spite of the numerous developments in the electrochemical sensing of arsenic, modification of working electrodes by deposition of NPs plays a significant role to increase electrochemical sensitivity and decrease LOD. In comparison to NPs, other sensory materials or even the bulk materials from which the NPs were made, cannot match the unique physical, electrical, and chemical properties that the NPs display.

No doubt, NPs due to their special physical and chemical properties are used for the modification of the electrode for better results like sensitivity, selectivity, etc. But there is a need to pay more attention to green synthesis methods that are eco-friendly and focus on the biosynthesis of the NPs from plants. Along with other requirements of measurement techniques, green synthesis of the NPs is the area where there are numerous opportunities for research to work for the betterment of measurement techniques of arsenic in water, especially low-cost sensors. There are specific scientific problems or gaps that still need to be solved, and future research should focus on the following key advancements:

Development of AI Powered Signals

Improved Accuracy and Pattern Recognition: AI models using machine learning algorithms can be trained to distinguish in arsenic signals from noise or irrelevant inputs at very low concentration. Example: Machine learning models trained on sensor data to distinguish arsenic signals from other contaminants.
Data-Driven Decision Making: AI can process large datasets from multiple sources (e.g., sensors, satellites) to map contamination and inform public health strategies. Example: AI-based GIS mapping tools identifying high-risk arsenic zones.
Automation and Smart Alerts: AI systems can automatically trigger alerts or initiate actions when arsenic levels exceed safe limits. Example: AI-integrated mobile apps alerting users when drinking water is unsafe.
Optimization of Sensor Performance: AI algorithms can self-calibrate sensors and optimize their response based on environmental conditions. Example: Adaptive AI algorithms adjusting sensor thresholds for seasonal water changes.

Use of Bio Inspired Materials

High Selectivity and sensitivity: Natural biomolecules like enzymes and peptides can selectively bind to arsenic, improving detection even in the presence of other contaminants. Example: Arsenic-binding proteins used in biosensors for specific detection of arsenite. DNA-based aptasensors with high sensitivity to trace arsenic levels.
Eco-Friendly, sustainable, and Non-Toxic: Using of plant-based materials like fruit peels or leaf extracts to avoids harmful byproducts commonly observed in synthetic sensors. Example: Green-synthesized gold nanoparticles using neem extract for arsenic sensing. Cellulose-based sensor platforms that decompose naturally after use.
Cost-Effective: Biomaterials are often cheaper and more sustainable than synthetic chemicals, making sensors more affordable. Example: Paper-based biosensors using natural reagents for low-cost field testing.

Hence the requirement of a technique, which is affordable and convenient like the portable kit and has the detection power of laboratory method and is environmentally risk-free are thrust area for the researchers. So, this review opens a scope for those working in the crucial field of determining arsenic and advancing it with little expense and less risk to health and the environment. By integrating AI, advanced nanomaterials, and economical engineering, researchers can develop sensors that are not just technologically sophisticated but also accessible, affordable, and actionable for communities most affected by arsenic contamination. Collaborative efforts among material scientists, engineers, policymakers, and local stakeholders will be critical to translating these innovations into real-world impact.

Supplementary Information

eer-2025-085-supplementary.pdf

Notes

Acknowledgments

The authors are grateful to their organization (University of Petroleum and Energy Studies) for the unconditional support and guidance during the writing of the paper.

Conflict of Interest

There is no conflict of interest. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Author Contributions

A.A. (Associate Professor) conceptualized and sketched the idea, supervised the overall data collection, and revised the final manuscript. V.K. (Post-doctoral Fellow) reviewed all the literature, revised, and edited the manuscript. K.R. (Professor) reviewed and edited the different sections of the manuscript. S.D. (Assistant Professor) revised and edited different sections of the final manuscript. A.D.S. (Assistant Professor) revised and edited different sections of the final manuscript. R.K.G.(Professor) reviewed and edited the manuscript. B.S.G. (Associate Professor) Revised and edited different sections of the final manuscript.

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Fig. 1

Organic and inorganic existence of Arsenic

Fig. 2

Different extraction/separation techniques for arsenic

Fig. 3

Major Gutzeit reactions involves in portable kits

Fig. 4

Major benefits and limitations of analytical and portable methods

Fig. 5

Schematic diagrams to represent the detection of arsenic with the electrochemical sensor. (Ref: Burakov et al. [51])

Table 1

Performance of different techniques for detection of arsenic in water.

Techniques	Time (mn)	LOD (ppb)	Sensitivity	Practical applicability	Reference
Lab (Analytical Techniques)
AAS	~ 30	0.0009-1	Moderate	Widely used in labs, moderate cost and maintenance	[16,27]
AFS	~ 10	0.0003-10	High	Excellent selectivity for arsenic As(III)/As(V)	[42–44]
ICP-MS	~ 30 sec	0.0003-1	Very High	Best for ultra-trace analysis; Expensive; need skilled operation	[31,43]
Portable (Based on Gutzet method)
Commercial Kit	Time per sample	LOD (Theoretical, Practical)	Sensitivity	Practical applicability	Reference
AAN	~ 5	(10, >20)	Low	Rural applications; limited accuracy below 20 ppb	[45–47]
MERK	~ 30	(10, >50)	Low	Field use; limited accuracy 50 ppb	[46,47]
NIPSOM	~ 30	(10, >20)	Low	Field use; limited accuracy < 20 ppb	[46,47]

Table 2

Features of electrode modifiers details of electrode materials and electro-analytical techniques used in the measurement of arsenic in water.

Electrode modifier	Electrode¹	Electrochemical techniques²	LOD (ppb)	Reference
Gold (AU) NPS	BDP	DPSAV	0.005	[86]
Gold (AU) NPS	GCE	SWASV	0.28	[87]
Gold (AU) NPS	NEE	SWASV	0.005	[88]
Platinum (Pt) NPS	GCE	LSV	2.1	[74]
Ruthenium (Ru) NPS	GCE	DPV	0.1	[89]
AU-Copper Bimetallic	GCE	SWASV	2.09	[90]
AU-Palladium Bimetallic	GCE	ASV	0.25	[91]
AU-Platinum Bimetallic	GCE	LSAV	0.28	[92]
MnOx/Au NP	GCE	LSAV	0.06	[65]
Fe₃O₄/ionic liquids	GCE	SWASV	0.0008	[93]
Graphene oxide	GCE	LSV	0.2	[94]
Carbon nanotube/Au NP	SPE	LSV	0.5	[95]

BDP: Boron-doped diamond, GCE: Glassy carbon electrode, NEE: Nanoelectrode ensemble, SPE: Screen-printed electrode,

ASV: Anodic stripping voltammetry, DPSAV: Differential pulse anodic stripping voltammetry, DPV: Differential pulse voltammetry, LSV: Linear stripping voltammetry, SWASV: Square wave anodic stripping voltammetry

Table 3

Summary of available reviews on arsenic detection from 2018 to 2025.

Title	Highlights	Reference
Critical review of bio/nanosensor for arsenic detection	The review highlights the basic chemical understanding of the sensor design. This review critically discussed the interaction between arsenic and related sensing molecules and indicated the significance of surface adsorption of different arsenic species.	[100]
Nano-Enabled sensors for the detection of arsenic in water	The review represents the detection mechanism of arsenic species that mainly focuses on the nano-enabled methods and fabrication of nanostructure/nanomaterials.	[101]
Role of nanocomposite materials in the development of electrochemical sensors for arsenic: Past, present, and future	The review critically highlights the use of modern materials in sensor creation with a focus on understanding their mechanisms. This review’s exact goal is to explain the developments of electrochemical sensors for the ultra-trace detection of inorganic arsenic in +3 or +5 oxidation states or total arsenic.	[102]
Nanomaterial-based sensors and biosensors for enhanced inorganic arsenic detection: A functional perspective	This review highlights the recent inorganic arsenic sensors and biosensors dependent on nanomaterials. The primary focus is on illustrating the numerous functions of nanoscale materials in these sensors and biosensors.	[103]
Nanomaterial-based aptamer sensors for arsenic detection	This review highlights the developments of nanomaterials-based aptamer sensors for arsenic detection and focuses on the optical and electrochemical strategies and their pros and cons.	[104]
Optical sensors for inorganic arsenic detection	An overview of optical techniques for measuring inorganic arsenic (+3 and +5) is given in this review article. The scattering, fluorimetric, and colorimetric techniques for inorganic arsenic detection are presented with a focus on the organic/biological molecules and their interaction with inorganic nanomaterials.	[105]