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).

The contamination of drinking water and food products by aluminium represents a serious health issue, as it is associated with chronic neurodegenerative diseases. Herein we report an analytical electrochemical method for the determination of aluminium(III) at glassy carbon electrodes, modified with commercially available tannic acid-capped gold nanoparticles. The combination of gold nanoparticles and tannic acid as capping/chelating agent results in an accurate and sensitive detection of aluminium(III) in aqueous solutions by square wave voltammetry (SWV). Employing the presented methodology, clear measurable signals are seen even at the low limit of 10.0 pM, markedly and usefully lower than the permissible level of 7.4 µM for drinking water as defined by the WHO and which compares favourably with alternative detection methods.

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We report an electrochemical sensor for the detection of lithium ions (Li +) in authentic human saliva at lithium manganese oxide (LiMn 2 O 4)-modified glassy carbon electrodes (LMO-GCEs) and screenprinted electrodes (LMO-SPEs). The sensing strategy is based on an initial galvanostatic delithiation of LMO followed by linear stripping voltammetry (LSV) to detect the re-insertion Li + in the analyte. The process was investigated using powder X-ray diffraction (PXRD) and voltammetry. LSV measurements reveal a measurable lower limit of 50.0 µM in both LiClO 4 aqueous solutions and synthetic saliva samples, demonstrating the applicability of the proposed analytical method down to low Li + concentrations. Four different samples of authentic human saliva were then analysed with the established sensing strategy using LMO-SPEs, showing good linearity over a concentration range up to 5.0 mM Li + with high reproducibility (RSD <7%) and applicability for routine monitoring purposes. The total time needed to analyse a sample is less than three minutes.

We report the electrochemical sensing of Hg2+ based on tannic acid capped gold nanoparticle (AuNP@TA) complexes. At optimal conditions using square wave voltammetry, the presented analytical method exhibits a "measurable lower limit" of 100.0 fM. This limit is considerably below the permissible level of 30.0 nM for inorganic mercury in drinking water, specified by the World Health Organization (WHO). The effect of potentially interfering ions, such as Zn2+ and Al3+, was studied and results indicate an excellent selectivity for Hg2+. The transfer of the proposed strategy onto AuNP@TA modified screen-printed electrodes demonstrates its applicability to routine monitoring of Hg2+ in tap water.