Trace Analysis of Heavy Metals (Cd, Pb, Hg) Using Native and Modified 3D Printed Graphene/Poly(Lactic Acid) Composite Electrodes

Abstract

Here we investigate the use of 3D printed graphene/poly(lactic acid) (PLA) electrodes for quantifying trace amounts of Hg, Pb, and Cd. We prepared cylindrical electrodes by sealing a 600 μm diameter graphene/PLA filament in a pipette tip filled with epoxy. We characterized the electrodes using scanning electron microscopy, Raman spectroscopy, and cyclic voltammetry in ferrocene methanol. The physical characterization showed a significant amount of disorder in the carbon structure and the electrochemical characterization showed quasi‐reversible behavior without any electrode pretreatment. We then used unmodified graphene/PLA electrode to quantify Hg, and Pb and Cd in 0.01 M HCl and 0.1 M acetate buffer using square wave anodic stripping voltammetry. We were able to quantify Hg with a limit of detection (LOD) of 6.1 nM (1.2 ppb), but Pb and Cd did not present measurable peaks at concentrations below ∼400 nM. We improved the LODs for Pb and Cd by depositing Bi microparticles on the graphene/PLA and, after optimization, achieved clear stripping peaks at the 20 nM level for both ions (4.1 and 2.2 ppb for Pb2+ and Cd2+, respectively). The results obtained for all three metals allowed quantification below the US Environmental Protection Agency action limits in drinking water.

Voltammetric pH Measurements in Unadulterated Foodstuffs, Urine, and Serum with 3D-Printed Graphene/poly(lactic Acid) Electrodes

“…The most attractive materials for 3D-printed electrochemical sensors are commercially available graphene-or carbon blackcontaining thermoplastics, which have been used for a number of applications in energy storage26,33-37 and chemical sensing. [38][39][40][41][42][43][44][45] These conductive thermoplastics are cheap and reliable electrode materials, but often require pretreatment to be useful for practical sensing applications because the conductive carbon is partially covered with plastic during the 3D-printing process. 46,47 The reactivity of carbon electrodes is extremely complex and the surface pretreatment has a significant impact on the observed voltammetry by controlling the nature and concentration of In this report, we developed 3D-printed voltammetric pH sensors using a commercially available graphene/poly(lactic acid) (PLA) filament by activating inherent quinone functional groups on the electrode surface.…”

“…SWVs of pH 4 40. Carmody buffer (black trace) fortified with 0.1 mM Pb2+ (red trace) and 0.1 mM Pb2+ and Cu2+.…”

Accounts in 3D‐Printed Electrochemical Sensors: Towards Monitoring of Environmental Pollutants

“…Alternatively, Walters et al investigated the use of 3D-printed BM cylinder electrodes for quantifying trace amounts of Hg, Pb and Cd using anodizing stripping voltammetry (ASV). [62] While Hg was easily measured at trace levels (detection limit: 6.1 nM) employing the unmodified electrode, Pb and Cd required the modification of the electrodes with Bi microparticles to achieve detection limits at the nM levels.…”

Voltammetric Determination of Pb(II) by a Ca-MOF-Modified Carbon Paste Electrode Integrated in a 3D-Printed Device

“…The developed MOF-based 3D-printed device presents distinct and significant advantages over existing MOF-based electrodes used for the ASV of Pb(II) [13][14][15][16][17]. The use of 3D-printing technology for the preparation of the device offers plenty of smart features including desktop-sized equipment, very low costs, production speed, strict control of the printing parameters, and ease of printing operation, while it generates negligible non-toxic waste [20][21][22][23][24][25][26][27][28][29][30][31][32]. The adopted process of mixing a small quantity of MOF with GP to produce the WE is by far simpler than drop-casting leading to stand-alone sensors, as the surface of the WE is renewed via a slight pressure on the syringe plunger.…”