Abstract
A novel Au nanoparticle (AuNP)-biopolymer coated carbon screen-printed electrode (SPE) sensor was developed through the co-electrodeposition of Au and chitosan for mercury (Hg) ion detection. This new sensor showed successful Hg2+ detection in landfill leachate using square wave anodic stripping voltammetry (SWASV) with an optimized condition: a deposition potential of −0.6 V, deposition time of 200 s, amplitude of 25 mV, frequency of 60 Hz, and square wave step voltage of 4 mV. A noticeable peak was observed at +0.58 V associated with the stripping current of the Hg ion. The sensor exhibited a good sensitivity of ~0.09 μA/μg (~0.02 μA/nM) and a linear response over the concentration range of 10 to 100 ppb (50–500 nM). The limit of detection (LOD) was 1.69 ppb, which is significantly lower than the safety limit defined by the United States Environmental Protection Agency (USEPA). The sensor had an excellent selective response to Hg2+ in landfill leachate against other interfering cations (e.g., Zn2+, Pb2+, Cd2+, and Cu2+). Fifteen successive measurements with a stable peak current and a lower relative standard deviation (RSD = 5.1%) were recorded continuously using the AuNP-biopolymer-coated carbon SPE sensor, which showed excellent stability, sensitivity and reproducibility and consistent performance in detecting the Hg2+ ion. It also exhibited a good reliability and performance in measuring heavy metals in landfill leachate.
Highlights
Mercury (Hg) pollution caused by industrial activity has been attracting global attention for decades [1,2,3]
We demonstrated direct Hg2+ detection in real landfill leachate samples using a Au nanoparticle (AuNP)-biopolymer-coated carbon screen-printed electrode (SPE) sensor
The AuNP and biopolymer nanocomposite was mixed at a 1:1 ratio (12 mg chitosan in 10 mL DI solution and 0.01 M HAuCl4 solution), which was stirred for 24 h at 60 ◦ C to achieve complete mixing
Summary
Mercury (Hg) pollution caused by industrial activity has been attracting global attention for decades [1,2,3]. Mercury occurs in many forms in aqueous solution depending on oxidation and reduction conditions [4]. The main forms of Hg exposure in the general population include methylmercury (MeHg) from seafood, inorganic mercury (I–Hg) from food, and mercury vapor (Hg0 ) from dental amalgam fillings [5]. Most Hg occurs in organic and inorganic forms of divalent mercury and Hg0 , as a form of Hg dissolved in an aqueous phase [6]. Once Hg has reached surface waters or soils, microorganisms convert it to MeHg, a substance that can be absorbed quickly by most organisms including marine life.
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