Electrochemical Detection of Ultratrace (Picomolar) Levels of Hg²⁺ Using a Silver Nanoparticle-Modified Glassy Carbon Electrode

Abstract

Ultratrace levels of Hg have been quantified by undertaking linear sweep voltammetry with a silver nanoparticle-modified glassy carbon electrode (AgNP-GCE) in aqueous solutions containing Hg. This is achieved by monitoring the change in the silver stripping peak with Hg concentration resulting from the galvanic displacement of silver by mercury: Ag(np) + 1/2Hg(aq) → Ag(aq) + 1/2Hg(l). This facile and reproducible detection method exhibits an excellent linear dynamic range of 100.0 pM to 10.0 nM Hg concentration with R = 0.982. The limit of detection (LoD) based on 3σ is 28 pM Hg, while the lowest detectable level for quantification purposes is 100.0 pM. This method is appropriate for routine environmental monitoring and drinking water quality assessment since the guideline value set by the US Environmental Protection Agency (EPA) for inorganic mercury in drinking water is 0.002 mg L (10 nM).

Highly Sensitive AgNP/MWCNT/Nafion Modified GCE-Based Sensor for the Determination of Heavy Metals in Organic and Non-organic Vegetables

“…It can be observed that the calibration sensitivity is greater in AAS than ASV. This suggests that AAS is more sensitive than ASV 17 . This only shows that the response is more prominent for every increment in concentration with AAS than with ASV.…”

“…9 . The peaks in the reverse scan suggest that the Ag ° from the forward scan re-reduce to Ag + and Ag 2+ thus separating the peaks in its respective voltage potential 17 .…”

“…Silver nanoparticles are proven to be excellent for modifying electrodes due to their high conductivity and high stability 16 . Different studies suggest that modified electrodes with AgNPs showed better limits of detection 17 , 18 . Multi-walled carbon nanotubes (MWCNTs) exhibit remarkable electrochemical properties because they have more electrochemically active sites, making them very attractive for electrochemical determination of heavy metals at low potentials 19 , 20 .…”

Grand Challenges in Nanomaterial-Based Electrochemical Sensors

“…Developing a sensor with a low LOD is crucial because often analytes exist at trace concentrations in real samples. Due to the innovation of nanomaterial-modified surfaces, LODs with values as low as picomole and femtomole levels have been achieved in the case of some ultra-sensitive sensors (Suherman et al, 2017;Li X. et al, 2018;Ponnaiah et al, 2018;Alizadeh et al, 2019;Wu et al, 2019;Gupta et al, 2020). For example, a sensor modified with open-ended CNTs was reported to have picomolar levels of sensitivity for the detection of neurotransmitters (Gupta et al, 2020).…”

“…For example, a sensor modified with open-ended CNTs was reported to have picomolar levels of sensitivity for the detection of neurotransmitters (Gupta et al, 2020). An ultrasensitive sensor for the detection of Hg 2+ was developed by modification of a glassy carbon electrode with silver nanoparticles resulting in picomolar level LOD values (Suherman et al, 2017). Yet, these modified surfaces remain challenging as they are not often as reproducible as one would hope.…”