Determination of four arsenic species in environmental water samples by liquid chromatography- inductively coupled plasma - tandem mass spectrometry

A paper-based visual colorimetric platform for rapid detection of arsenic in the environment

Arsenic is a highly toxic heavy metal that poses significant environmental and health risks. Major sources of arsenic pollution include wastewater and waste discharges from industrial and mining activities, as well as arsenic-containing pesticides and herbicides used in agriculture. This study employed the arsenic spot method, utilizing test strips prepared with mercury bromide as a reactive sensor, to conduct semi-quantitative detection of inorganic arsenic in water, soil, and oil field chemicals used in oil extraction processes. Detection was performed through colorimetric analysis. Experimental results revealed the following detection limits for the test strip: 0.05 mg L-1 for water samples, 0.25 mg L-1 for soil samples, and 0.05 mg L-1 for water-soluble oil field chemicals. The detection results aligned with those obtained via inductively coupled plasma mass spectrometry, confirming the reliability of the method. Consequently, the arsenic spot colorimetry technique is a rapid and effective tool for the semi-quantitative determination of inorganic arsenic in various samples, significantly reducing analysis time.

Analytical techniques for arsenic speciation

Due to its toxicity, contamination with arsenic, a Group 1 carcinogen, is a significant environmental and public health issue. The toxicity of arsenic varies with its chemical form. For example, inorganic species like arsenite (AsO33-) and arsenate (AsO43-) are generally more toxic than organoarsenic compounds. However, some organoarsenic species exhibit higher toxicity than inorganic species. Therefore, the precise quantification and speciation of arsenic is necessary. Chromatographic techniques, particularly liquid chromatography coupled with inductively coupled plasma mass spectrometry (LC-ICP-MS), are widely used for arsenic speciation owing to their high sensitivity and accuracy. Gas chromatography-mass spectrometry (GC-MS) is another effective technique for detecting arsenic species after derivatization. In addition to chromatographic methods, more straightforward and cost-effective techniques are available for inorganic arsenic speciation. These include adsorption techniques, colorimetric assays such as the molybdenum blue method, hydride generation reactions, and voltammetry. Emerging technologies, such as microfluidic and electrochemical devices, enable rapid and portable analysis, facilitating in situ detection of arsenite and arsenate in environmental samples. While LC-ICP-MS remains the gold standard for comprehensive arsenic speciation, other advanced technologies provide a practical, rapid, and cost-effective approach.

A brief note on substantial sub-daily arsenic variability in pumping drinking-water wells in New Hampshire

Large variations in redox-related water parameters, like pH and dissolved oxygen (DO), have been documented in New Hampshire (United States) drinking-water wells over the course of a few hours under pumping conditions. These findings suggest that comparable sub-daily variability in dissolved concentrations of redox-reactive and toxic arsenic (As) also may occur, representing a potentially critical public-health data gap and a fundamental challenge for long-term As-trends monitoring. To test this hypothesis, discrete groundwater As samples were collected approximately hourly during one day in May and again in August 2019 from three New Hampshire drinking-water wells (2 public-supply, 1 private) under active pumping conditions. Collected samples were assessed by laboratory analysis (total As [AsTot], As(III), As(V)) and by field analysis (AsTot) using a novel integrated biosensor system. Laboratory analysis revealed sub-daily variability (range) in AsTot concentrations equivalent to 16 % - 36 % of that observed in the antecedent 3-year bimonthly trend monitoring. Thus, the results indicated that, along with previously demonstrated seasonality effects, the timing and duration of pumping are important considerations when assessing trends in drinking-water As exposures and concomitant risks. Results also illustrated the utility of the field sensor for monitoring and management of AsTot exposures in near-real-time.

Update of the risk assessment of inorganic arsenic in food

The European Commission asked EFSA to update its 2009 risk assessment on arsenic in food carrying out a hazard assessment of inorganic arsenic (iAs) and using the revised exposure assessment issued by EFSA in 2021. Epidemiological studies show that the chronic intake of iAs via diet and/or drinking water is associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung. The CONTAM Panel used the benchmark dose lower confidence limit based on a benchmark response (BMR) of 5% (relative increase of the background incidence after adjustment for confounders, BMDL05) of 0.06 μg iAs/kg bw per day obtained from a study on skin cancer as a Reference Point (RP). Inorganic As is a genotoxic carcinogen with additional epigenetic effects and the CONTAM Panel applied a margin of exposure (MOE) approach for the risk characterisation. In adults, the MOEs are low (range between 2 and 0.4 for mean consumers and between 0.9 and 0.2 at the 95th percentile exposure, respectively) and as such raise a health concern despite the uncertainties.

Arsenic speciation in freshwater fish: challenges and research needs

Food and water are the main sources of human exposure to arsenic. It is important to determine arsenic species in food because the toxicities of arsenic vary greatly with its chemical speciation. Extensive research has focused on high concentrations of arsenic species in marine organisms. The concentrations of arsenic species in freshwater fish are much lower, and their determination presents analytical challenges. In this review, we summarize the current state of knowledge on arsenic speciation in freshwater fish and discuss challenges and research needs. Fish samples are typically homogenized, and arsenic species are extracted using water/methanol with the assistance of sonication and enzyme treatment. Arsenic species in the extracts are commonly separated using high-performance liquid chromatography (HPLC) and detected using inductively coupled plasma mass spectrometry (ICPMS). Electrospray ionization tandem mass spectrometry, used in combination with HPLC and ICPMS, provides complementary information for the identification and characterization of arsenic species. The methods and perspectives discussed in this review, covering sample preparation, chromatography separation, and mass spectrometry detection, are directed to arsenic speciation in freshwater fish and applicable to studies of other food items. Despite progress made in arsenic speciation analysis, a large fraction of the total arsenic in freshwater fish remains unidentified. It is challenging to identify and quantify arsenic species present in complex sample matrices at very low concentrations. Further research is needed to improve the extraction efficiency, chromatographic resolution, detection sensitivity, and characterization capability.

A review on arsenic in the environment: contamination, mobility, sources, and exposure

Arsenic is one of the regulated hazard materials in the environment and a persistent pollutant creating environmental, agricultural and health issues and posing a serious risk to humans. In the present review, sources and mobility of As in various compartments of the environment (air, water, soil and sediment) around the World are comprehensively investigated, along with measures of health hazards. Multiple atomic spectrometric approaches have been applied for total and speciation analysis of As chemical species. The LoD values are basically under 1 μg L-1, which is sufficient for the analysis of As or its chemical species in environmental samples. Both natural and anthropogenic sources contributed to As in air, while fine particulate matter tends to have higher concentrations of arsenic and results in high concentrations of As up to a maximum of 1660 ng m-3 in urban areas. Sources for As in natural waters (as dissolved or in particulate form) can be attributed to natural deposits, agricultural and industrial effluents, for which the maximum concentration of 2000 μg L-1 was found in groundwater. Sources for As in soil can be the initial contents, fossil fuel burning products, industrial effluents, pesticides, and so on, with a maximum reported concentration up to 4600 mg kg-1. Sources for As in sediments can be attributed to their reservoirs, with a maximum reported concentration up to 2500 mg kg-1. It is notable that some reported concentrations of As in the environment are several times higher than permissible limits. However, many aspects of arsenic environmental chemistry including contamination of the environment, quantification, mobility, removal and health hazards are still unclear.