Trace Hg Research Articles

Transition metal doped ZIF‐8 for the detection of the heavy metal Hg(II)

AbstractThe effects of heavy metals such as Hg(II) and Pb(II) on the human body are profound. Moreover, they pose significant concerns due to industrial development. Thus, the rapid and stable detection of heavy metal ions and related chemicals has emerged as an urgent issue. The application of Differential Pulse Stripping Voltammetry (DPSV) facilitated accurate and rapid detection of Hg2+ utilizing MOF materials and ZIF‐8 as detection agents. Pure ZIF‐8 served as the substrate material. Copper or nickel ions were individually introduced into the substrate material. This process resulted in the formation of bimetallic MOF materials. These materials were designated as CuZn and NiZn, respectively. Transition metal‐doped materials were used to modify the glassy carbon electrode (GCE), resulting in a substantial enhancement in the detection performance of Hg2+. The CuZn/GCE configuration demonstrated the most significant enhancement. When compared to a GCE modified with pure ZIF‐8, both sensitivity and the detection limit for free Hg2+ in the environment experienced increases of 450% and 64%, respectively. Stability and repeatability tests were conducted on the CuZn‐modified GCE. Results indicated that the electrode proved to be very stable and showed strong selectivity in the presence of interfering ions. The sensor modified with CuZn shows promising potential for monitoring trace Hg2+ levels.

In-situ deposition of gold nanoparticles on screen-printed carbon electrode for rapid determination of Hg2+ in water samples

Herein, an electrochemical sensor for Hg2+ detection using in-situ deposited gold nanoparticles modified screen-printed carbon electrode (SPCE) was developed. The gold nanoparticles and Hg were co-deposited on the electrode during the enrichment process. Scanning electron microscope (SEM) and Energy dispersive X-ray (EDX) spectrum prove the successful modification of gold nanoparticles. After modification, the active surface area of the electrode enlarged, the electron transfer ability enhanced, and the detection of Hg2+ became possible. After comprehensive optimization of experimental parameters, the proposed sensor can achieve rapid detection of trace Hg2+ in drinking water through differential pulse stripping voltammetry (DPSV). The limit of detection reaches 0.33 μg/L, the linear range is 0.5–80 μg/L. The test can be completed within 5 min. This sensor does not require extra electrode modification before detection, which can simplify experimental steps and improve detection efficiency, holding great promise for the on-site detection of Hg2+ in environmental and food samples.

Bionanomaterial composed of Bradyrhizobium japonicum and graphene oxide for determination of mercury in water and fruit juice samples

In the present work, the synthesis of a novel hybrid bionanomaterial formed by the bacteria Bradyrhizobium japonicum (BJ) and the graphene oxide (GO) nanomaterial implemented in the miniaturized dispersive microsolid phase extraction technique (D-μ-SPE) was reported for the first time for the preconcentration and determination of Hg in water and fruit juice samples after a multivariate optimization. Selective Hg extraction was achieved by forming a complex with ammonium pyrrolidinedithiocarbamate (APDC) reagent and a multivariate study was performed to optimize the experimental conditions. The optimal Hg extraction conditions for 25 mL of sample were 3 mg of BJ@GO, NaNO3 at 1% (w/v), 6 min of vortex agitation and 9 min of centrifugation. For back extraction, 500 µL of 14 mol L−1 HNO3, 6 min of vortex agitation and 6 min of centrifugation were used followed by detection by cold vapor atomic fluorescence spectrophotometry (CV-AFS). Under optimized experimental conditions, an extraction efficiency of 98%, a detection limit of 0.08 µg L−1, a relative standard deviation of 3.5% (at 1 µg L−1 of Hg, n = 10), and a linear range of 0.26 - 4.0 µg L−1 were obtained. In addition, the sustainability of the method developed through the use of the Analytical GREEnness calculator (AGREE) software was evaluated, obtaining a greenness degree of 0.59. This work reports the first application of BJ@GO along with the D-μ-SPE technique for trace Hg determination water and fruit juice samples. In this way, this research work allows the exact and precise determination of low Hg concentrations in water and juice samples, which allows the evaluation of the contamination degree by this toxic metal in beverages widely consumed by the population.

A rapid Surface-Enhanced Raman scattering method for the determination of trace Hg2+ with tapered optical fiber probe

Surface-enhanced Raman scattering (SERS) offers a route for trace detection of mercury ions (Hg2+) owing to its great enhancement near the surface of the substrate. However, most of the methods are inconvenient due to the long reaction time and the strict measurement conditions. Based on a reaction between silver nanoparticles (AgNPs) and mercury ions, a simple but effective method is proposed in this paper. In the experimental research, a tapered optical fiber (TOF) modified with AgNPs is employed as a sensing probe and Rhodamine 6G (R6G) is taken as the Raman reporter. The SERS substrate is consumed by the Hg2+, causing a spectrum decrease. In the Hg2+ concentration range of 10−12 M to 10−4 M, the spectra evolution is detected using a mobile Raman spectrometer. By analyzing the decrease of the Raman peak after a 5-minutes interval, the concentration of Hg2+ can be quantified. A limit of detection of 5.15 × 10−13 M is achieved, which is much below the maximum Hg2+ content of drinkable water specified by USEPA (10−8 M). Verification tests were performed with the inductively coupled plasma-mass spectrometry (ICP-MS), the results showed that the proposed SERS method is effective for real samples detection. In addition, the reproductivity and the selectivity are experimentally confirmed. With this reliable, rapid, ultrasensitive and accurate method, trace Hg2+ could be detected in many applications.

Preconcentration and selective extraction of trace Hg(ii) by polymeric g-C3N4 nanosheet-packed SPE column.

In this study, we successfully synthesized polymeric graphitic carbon nitride (g-C3N4) nanosheets through thermal means and proposed their application in solid-phase extraction (SPE) for the enrichment of trace Hg(ii). The nanosheets underwent characterization using scanning electron microscopy, tunnelling electron microscopy, and energy-dispersive X-ray spectroscopy. The column packed with polymeric carbon nitride nanosheets demonstrated effective extraction of trace Hg(ii) ions from complex samples. The g-C3N4 nanosheets possess a zeta potential value of -20 mV, enabling strong interaction with positively charged divalent Hg(ii) ions. This interaction leads to the formation of stable chelates with the nitrogen atoms present in the polytriazine and heptazine units of the material. The proposed method exhibited a high preconcentration limit of 0.33 μg L-1, making it suitable for analysing trace amounts of Hg(ii) ions. Moreover, the method's applicability was confirmed through successful analysis of real samples, achieving an impressive preconcentration factor of 200. The detection limit for trace Hg(ii) ions was determined to be 0.6 μg L-1. To assess the accuracy of the method, we evaluated its performance by recovering spiked amounts of Hg(ii) and by analysing certified reference materials. The results indicated excellent precision, with RSD consistently below 5% for all the analyses conducted. In conclusion, the thermally synthesized polymeric carbon nitride nanosheets present a promising approach for solid-phase extraction and preconcentration of trace Hg(ii) from real samples. The method showcases high efficiency, sensitivity, and accuracy, making it a valuable tool for environmental and analytical applications.

Constructing an eco-friendly and ratiometric fluorescent sensor for highly efficient detection of mercury ion in environmental samples.

Mercury ion (Hg2+) is a highly toxic and ubiquitous pollutant, whose effective detection has aroused widespread concern. A novel ratiometric fluorescent sensor has been designed to rapidly and efficiently detect Hg2+ based on blue/red carbon dots (CDs) with environmental friendliness. This sensor was well characterized via TEM, FTIR, XPS, UV-vis, and zeta potential analysis and displayed excellent fluorescence properties and stability. The fluorescence of blue CDs at 447nm was significantly quenched with the addition of Hg2+ resulted from the static quenching, whereas that of red CDs at 650nm remained invariable. A sensitive method for Hg2+ determination was constructed in the range of 0.05-7.0nmolmL-1 with optimal conditions, and the detection limit was down to 0.028nmolmL-1. Meanwhile, compared to other 17 metal ions, the ratiometric fluorescent sensor exhibited high selectivity for Hg2+. Furthermore, satisfied recoveries had also been obtained for measuring trace Hg2+ in practical environmental samples. This developed ratiometric fluorescent sensor provided a reliable, environmental-friendly, rapid, and efficient platform for the detection of Hg2+ in environmental applications.

Enhancing peroxidase-like activity of AuNPs through headspace reaction: A signal amplification strategy for colorimetric and fluorescent sensing of trace Hg2+

BackgroundRecently, headspace single-drop microextraction (HS-SDME) has attracted some attention for developing sensitive and selective colorimetric assays due to its excellent capability to reduce matrix interference and enrich analytes. However, the single droplet limits direct visual observation of color change and its quantitative measurement suffers from reduced optical path length. Therefore, amplifying the detection signals in both volume and intensity is an important and challenging task for improving the sensitivity, stability, and accuracy of such colorimetric analysis. ResultsIn this study, a "headspace-nanoenzyme" (HS-NE) strategy was proposed that successfully addressed these challenges and enabled the colorimetric and fluorescent dual-mode detection of trace Hg2+. Atomic Hg0, generated via chemical vapor generation (CVG), underwent headspace reaction with AuNPs droplet to form Au@HgNPs, thus catalyzing the oxidation of o-phenylenediamine (OPD) in the presence of H2O2. The absorbance and fluorescence intensity of oxidized OPD were proportion to the concentration of Hg2+ in the sample solution. Due to the greatly enhanced peroxidase-like activity by Au@HgNPs, the limit of detection was as low as 0.98 nM and 0.21 nM for the colorimetric and fluorescent modes, respectively. The applicability of this assay was further demonstrated with determination of Hg2+ in real environmental and biological samples. Moreover, a convenient and cost-effective paper-based sensing platform was fabricated for rapid on-site detection of Hg2+. Significance and noveltyThis novel HS-NE strategy combines HS-SDME and nanoenzyme-based sensing to achieve dual effects of eliminating matrix interference and amplifying the measurement signal, resulting in improved accuracy, enhanced stability, high sensitivity, and exceptional selectivity, with great potential for on-site determination of trace Hg2+.

MoS2/Au heterojunction nanostructures for electrochemical detection of trace Hg(II) in wastewater samples

In this study, a highly sensitive electrochemical sensor was developed for the detection of mercury ions in wastewater samples. The sensor was constructed using MoS2/Au heterojunction nanostructures, which involved depositing plasmonic Au nanoparticles onto MoS2 nanosheets on screen-printed carbon electrodes. The MoS2/Au-SPCE sensor demonstrated outstanding electrochemical sensing capabilities, attributed to the emergence of a mid-gap state across the Fermi level. This state arises from the interaction between the Au 5d (Au, +1 charge state) and Mo 3d (MoS2, +4 charge state) orbitals. This performance was superior to that of single Au nanoparticles and MoS2. The sensor showed high sensitivity in detecting Hg(II) ions with a wide linear range from 0.02 ppm to 0.0004 ppb and a LOD of 0.0004 ppb. The developed sensor was effectively applied for the detection of Hg(II) ions in factory wastewater and other samples. The MoS2/Au-SPCE sensor was successfully used to detect low concentrations of 565.0 ppb and 92.0 ppb Hg(II) in the investigated samples. This study introduces a new electrochemical sensor, leveraging the MoS2/Au heterostructures, meticulously crafted for the intricate sensing of Hg(II) ions

A novel thioketal containing fluorescent dye for mercury(II) detection via Hg2+-triggered ACQ to AIE transformation

A novel thioketal containing fluorescent dye 1OS was elaborately designed for mercury(II) determination, which not only integrated the benefits of the remarkable specificity of Hg2+-promoted deprotection reaction and the robust emission of AIEgen in aggregated state, but also provided a surprising platform for ACQ-to-AIE switching, i.e. Hg2+-triggered ACQ to AIE transformation. Once encountered Hg2+ ions, the deprotection reaction happened immediately within seconds, accompanied with a conversion of 1OS (ACQ) to 1O (AIE). Excitedly, the probe shows remarkable selectivity and specificity towards Hg2+ both in solution, aggregated and solid states with significant fluorescence color change. When added trace Hg2+ ions into 1OS solution, its PL intensity declined completely with emission color changed from bright green to darkness with LOD as 0.36 μM. Oppositely, a “turn on” signal was achieved in the aggregated state (fw = 98 %), which exhibited a dramatically enhancement of PL intensity along with fluorescent emission altered from darkness to brilliant yellow. Other common metal cations gave no interference to the probe. Meanwhile, the constructed test strip could “turn on” signify Hg2+ in water solution.

Miniaturized point discharge optical emission spectrometry coupling with solid phase extraction: A robust approach for sensitive quantification of total mercury in mung bean sprout growth.

In this work, a portable chemical vapor generation point discharge optical emission spectrometry (CVG-PD-OES) system was designed for trace Hg2+ monitoring in mung bean sprout samples. The system incorporated selective solid phase extraction (SPE) to enhance the detection sensitivity. Gold nanoparticles (AuNPs) were prepared and utilized to extract trace amounts of Hg2+ by forming gold amalgam. Subsequently, the amalgam was desorbed using 5% HCl and introduced into a low-power PD-OES system analysis via CVG. A low limit of detection (LOD) of 0.16ngmL-1 was obtained with a linear range of 0.5-6ngmL-1. The well-designed system was successfully utilized for monitoring trace Hg2+ in the growth of mung beans. The results indicated that the Hg2+ in mung bean sprouts was continuously decreased during growth based on the metabolism. Furthermore, the risk assessment conducted implied a negligible hazard quotient, suggesting that the observed levels of exposure posed minimal risk.

Facile and sensitive detection of mercury ions based on fluorescent structure-switching aptamer probe and exonuclease Ⅲ-assisted signal amplification

Hg2+ is highly toxic to human health and ecosystem. In this work, based on the unique fluorescent property of 2-Aminopurine (2-AP), the formation of T-Hg2+-T mismatch structure and the signal amplification of exonuclease III (Exo III) assisted target cycle, a fluorescent probe for facile and sensitive detection of Hg2+ is constructed. The hairpin-looped DNA probe is rationally designed with 2-AP embedded in the stem and thymine-rich recognition overhangs extended at the termini. The cleavage of the double stranded DNA stem with stable T-Hg2+-T pairs catalyzed by Exo III is prompted to happen upon recognition of trace Hg2+. Under the optimal reaction conditions, there is an excellent linear relationship between Hg2+ concentration and fluorescence intensity in the range of 7.5–200 nM with a detection limit of 0.38 nM. In addition, the detection results of Hg2+ in Songhua River water and fish samples are satisfactory. The fluorescent probe avoids labeling additional quenchers or quenching materials and has strong anti-interference ability. Thus, the fluorescent probe has a broad prospect in practical application.

One-step and real-time detection of Hg2+ in brown rice flour using a biosensor integrated with AC electrothermal enrichment.

Mercury (Hg2+) is one of the most toxic heavy metals in farm products, so rapid detection of trace Hg2+ has always been sought after with high interest. Herein, we report a biosensor to specifically recognize Hg2+ in leaching solutions of brown rice flour. This sensor is simple and of low cost, with a very short assay time of 30s. Another merit is the ultra-low limit of detection (LOD) at fM level. In addition, the specific aptamer probe realizes a good selectivity above 105: 1 against the interferences. This sensor is developed based on an aptamer-modified gold electrode array (GEA) for capacitive sensing. Alternating current electrothermal (ACET) enrichment is induced during the AC capacitance acquirement. Thus, the enrichment and detection are coupled as a single step, and pre-concentration is needless. Owing to the sensing mechanism of solid-liquid interfacial capacitance and ACET enrichment, Hg2+ level can be sensitively and rapidly reflected. Also, the sensor has a wide linear range from 1 fM to 0.1nM and a shelf life of 15days. This biosensor shows advantages on overall performance, enabling easy-to-operate, real-time, and large-scale Hg2+ detection in farm products.

In situ microwave-assisted preparation of NS-codoped carbon dots stabilized silver nanoparticles as an off-on fluorescent probe for trace Hg2+ detection

An off-on fluorescent probe (NS-CDs-AgNPs) was synthesized based on a one-pot microwave process by utilizing N, S co-doping carbon dots (NS-CDs) and silver nitrate as precursors. The significant peak of NS-CDs-AgNPs at 393 nm in ultraviolet spectrum indicated silver nanoparticle (AgNPs) were successfully synthesized. A faint blue fluorescence emission (442 nm) was displayed when excited NS-CDs-AgNPs at 371 nm. A remarkable fluorescence recovery was observed upon adding of trance Hg2+, whereas the other heavy metal ions did not elicit this response. The reason for this phenomenon was revealed in this work that a spontaneous redox reaction occurred between NS-CDs-AgNPs and Hg2+, which leaded to the formation of NS-CDs-Agn-2NPsHg complexes. On the basis of this mechanism, a new off-on fluorescent analytical method was constructed for Hg2+ detection with linear range of 10–400 nM (R2 = 0.9941), and the detection limit (LOD) of 5.16 nM. Additionally, satisfactory recovery (90.28%–106.13%) and the relative standard deviation (RSD) (RSD＜5.21%) were obtained in water sample detection. More importantly, the NS-CDs-AgNPs exhibited lower cytotoxicity and better biocompatibility, indicating a huge potential in cell imaging and clinical medicine.

Gold nanoparticle-modified sustainable plastic sensor chip for voltammetric monitoring of Hg(II)

Mercury is a toxic environmental contaminant that can cause serious health problems. This work describes a new type of eco-friendly three-electrode plastic sensor chip for the determination of trace Hg(II) by means of anodic stripping voltammetry (ASV). The sensor chip is entirely fabricated by injection moulding, which is a sustainable manufacturing method, and consists of three conductive carbon-based electrodes embedded in a plastic holder while the reference electrode is coated with Ag using e-beam evaporation. The sample is spiked with Au(III) which deposits on the working electrode in the form of gold nanoparicles during the analysis; the target Hg(II) co-deposits on the gold nanoparticles forming a Au(Hg) amalgam in situ. The accumulated Hg is stripped off the electrode and quantified by an anodic square wave potential scan. The relevant conditions and the potential interferences are investigated. The limit of detection for Hg(II) is 0.4 μg L−1 and the repeatability at the 20 μg L−1 Hg(III) level (n = 10) is 5.3%. The sensor is applied to water, honey, fish oil and mussel samples with recoveries between 98 and 107%.

An interesting fluorescent probe with aggregation-induced emission for highly sensitive and selective detection of Hg2+

The development of highly sensitive analytical methods for detection of trace level of mercury (II) has always arouse great interests owing to its notoriously toxicity to natural environment and human health. In this paper, an interesting “turn-on” fluorescent probe L for detection of Hg2+ based on 2-hydroxy-1-naphthaldehyde derivative was synthesized, and its chemical structure was confirmed by IR, 1H NMR, 13C NMR, ESI-MS and single crystal. Probe L exhibits aggregation-induced emission properties and provides a simple and efficient strategy for highly selective and sensitive detection of Hg2+ in an aqueous solution of DMSO/H2O (1:4, v:v). According to job curve and fluorescence titration, probe L with Hg2+ forms a 1:1 ratio of complex, and its lowest detection limit is 6.35×10−9 mol/L. Probe L toward detection of Hg2+ presents significant advantages such as low-cost, structural stability, high water solubility, rapid response and allowing their long-term use. The potent applicants for probe L were also investigated and indicated it could conveniently be made a series of sensor strips and applied to rapidly detect trace Hg2+ in traditional Chinese medicine.

4-Mercaptopyridine-Modified Sensor for the Sensitive Electrochemical Detection of Mercury Ions

As a highly toxic heavy metal ion, mercury ion (Hg2+) pollution has caused serious harm to the environment and human health. In this paper, 4-mercaptopyridine (4-MPY) was selected as the sensing material and decorated on the surface of a gold electrode. Trace Hg2+ could be detected by both differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) methods. The proposed sensor displayed a wide detection range from 0.01 μg/L to 500 μg/L with a low limit of detection (LOD) of 0.002 μg/L by EIS measurements. Combined with molecular simulations and electrochemical analyses, the chelating mechanism between Hg2+ and 4-MPY was explored. Through the analysis of binding energy (BE) values and stability constants, 4-MPY showed an excellent selectivity for Hg2+. In the presence of Hg2+, the coordination of Hg2+ with the pyridine nitrogen of 4-MPY was generated at the sensing region, which caused a change in the electrochemical activity of the electrode surface. Due to the strong specific binding capability, the proposed sensor featured excellent selectivity and an anti-interference capability. Furthermore, the practicality of the sensor for Hg2+ detection was validated with the samples of tap water and pond water, which demonstrated its potential application for on-site environmental detection.

Detection of Trace Hg(II) in Cosmetics and Aqueous Solution by a Gold Nanospikes Electrochemical Sensor

An ultrasensitive and rapid electrochemical detection of trace Hg(II) sensor was developed. The significantly amplified electrochemical signals was caused by the high specific surface area of the electrochemical sensor. Scanning electron microscopy showed that the gold nanospikes were 200 ∼ 300 nm in length and 50 nm in diameter. The electrochemical properties of sensor were characterized by square wave voltammetry. Experimental parameters were optimized using square wave stripping voltammetry. The linear range of sensor for Hg(II) is 3 × 10−10 mol l−1 ∼ 7 × 10−7 mol l−1 and the limit of detection is 1 × 10−10 mol l−1. Hg(II) was successfully quantified in river water and cosmetics. The original Hg(II) in loose powder, Sunblock and whitening lotion using the high ratio surface area electrochemical sensor determination were found to be 2.234, 2.056 and 2.347 mg kg−1 respectively. The results are within the range of standard values, the RSD are 1.7%, 1.5% and 2.1%, respectively. HRSA Au electrode sensor displays high sensitive, excellent stability, reproducibility, especially more convenient than ICP-MS and AFS verification methods. We look forward to the possibility that the HRSA Au electrode sensor can be used for real-time monitoring of Mercury ions in water and cosmetics in the future.

A reversible CHEF-based NIR fluorescent probe for sensing Hg2+ and its multiple application in environmental media and biological systems

Hg2+ poses a great threat to human health and the environment due to its bioaccumulation and permanent damage. Herein, a reversible CHEF-based near-infrared fluorescent probe 2-(3-((E)-4-((E)-4-(diethylamino)-2- hydroxybenzylidene)amino)styryl)-5,5-dimethylcyclohex-2-en-1-ylidene)propanedinitrile (DHEY) capable of specifically recognizing Hg2+ was constructed. DHEY exhibits advantages of large Stokes shift (157 nm), excellent selectivity, high sensitivity (LOD = 3.2 μg/L), and fast response efficiency (<3 min). Interestingly, DHEY can also realize rapid and effective detection of Hg2+ after being recycled 7 times. The successful recovery of trace Hg2+ in different environmental water samples fully demonstrates the potential of DHEY for actual applications. In particular, DHEY enables real-time observation of the distribution and translocation pattern of exogenous Hg2+ in HeLa cells and zebrafish. This work provides important theoretical support for investigating the fate of heavy metal ions in the environment using fluorescence techniques.

Ultrasonic assisted magnetic solid phase extraction of ultra-trace mercury with ionic liquid functionalized materials

Due to the agglomeration between particles, the inherent adsorption characteristics of magnetic powder materials are usually difficult to fully display. Taking ionic liquid functional materials as an example, the enrichment behavior of these adsorbents for trace mercury (Hg2+) in ultrasonic (US) assisted dispersion mode was systematically studied. The dissociation of protonic ionic liquids (IL) occur in the process of dispersion and the strong electrostatic attraction can improve the diffusion and adhesion of mercury on the adsorbent surface. Spectral measurement data showed that with the help of US, the more uniform dispersion of magnetic materials accelerated the adsorption of trace Hg2+. Ultrasonic intrinsic parameters such as frequency, power and radiation duration significantly affect the dispersion and apparent adsorption properties of magnetic functional materials. In the range of experimental parameters, the dye/paper image experimental results documents that there is a positive correlation between cavitation effect and ultrasonic frequency/power. The enrichment degree of fixed adsorbate (0.1 μg L−1) under high frequency (59 kHz) or high-power input (100%) is 1–2 times higher than that under low frequency (40 kHz) or low power (60%) input. This is a valuable conclusion for the subsequent study of US dispersion of magnetic and even non-magnetic powder materials. In addition, the in-situ desorption and accurate measurement of adsorbed mercury were realized by combining slurry vapor generation atomic fluorescence spectroscopy (SVG-AFS). The constructed US assisted magnetic solid phase extraction (US-MSPE) method has the characteristics of low detection limit (0.36 ng L−1), high recovery (>90%), sustainable utilization (>3) and reasonable measurement deviation (<5%), which can meet the requirements of ultra-trace Hg2+ (0.01–1.0 μg L−1).

Porous-polymer monolith decorated with dithizone for greener visual and spectrophotometric sensing of Hg(II)

This paper describes a hydrophobic porous polymer monolith for visual and spectrophotometric determination of Hg(II). The monolith was synthesized in the coffins of 2.0 mm i.d. transparent polypropylene ink-pen tubes using stearyl methacrylate (SMA) as the functional monomer and ethylene glycol dimethacrylate (EDMA) as the crosslinker by fast UV-mediated polymerization. The poly(SMA-co-EDMA) monolith retained dithizone, an anchor for the Hg(II) and colorimetric reagent. Besides the monolith's fast preparation, the polypropylene transparency enabled the naked-eye visualization of all color changes occurring in the solid phase extraction steps (conditioning, loading, washing and elution). This feature also enabled the unprecedented use of a simple ruler for detection since the distance occupied by Hg(II) inside the column was linearly related to Hg(II) concentration. Loading the column with 12.0 mL of sample and elution with 1.0 mL of ethanol contributed to the green analytical chemistry and provided a detection limit of 7.9 µg L−1, which was enough to determine Hg(II) in certified estuarine sediment (ERM-CC580) and urine samples. A sample volume of 45 mL provides a detection limit of 0.59 μg L−1, allowing the detection of trace Hg(II) levels in the Billings reservoir waters, an anthropized water reservoir located in the São Paulo Metropolitan Area of São Paulo State (Brazil), thus attending the maximum concentration levels preconized by the United States Environmental Protection Agency (1.0 µg L−1) and World Health Organization (6.0 µg L−1). The proposed method is simple, cheap and can be easily implemented in field measurements for sample trials.