Heavy metals such as lead, mercury, cadmium, zinc and copper are among the most important pollutants because of their non-biodegradability and toxicity above certain thresholds. Here, we review methods for sensing heavy metal ions (HMI) in water samples using screenprinted electrodes (SPEs) as transducers. The review (with 107 refs.) starts with an introduction into the topic, and this is followed by sections on (a) mercury-coated SPEs, (b) bismuth-coated SPEs, (c) gold-coated SPEs (d) chemically modified and non-modified carbon SPEs, (e) enzyme inhibition-based SPEs, and (f) an overview of commercially available electrochemical portable heavy metal analyzers. The review reveals the significance of SPEs in terms of decentralized and of in situ analysis of heavy metal ions in environmental monitoring.

Two graphene oxide (GO) materials with different layer size and proportion of functional groups in the basal planes (hydroxyl and epoxy) and in the edges (carbonyl and carboxyl) were used to modify the surface of commercially available screen printed electrodes. Cyclic voltammetry in 0.1 M KNO 3 was evaluated as an easy to use electrochemical methodology to reduce GO attached to the surface of screen-printed electrodes (SPEs). A cathodic peak related to the reduction of GO was identified, and the peak potential was correlated to the difficulty to reduce GO to Electrochemically Reduced Graphene Oxide (ERGO) depending on the functional groups present in the basal plane and in the edges of the original GO monolayers. Time resolved UV-VIS absorption spectroelectrochemistry in near-normal reflection mode on a screen-printed electrode is used for the very first time as an in-situ characterization technique for real time monitoring unambiguously the electrochemical reduction of graphene oxide.

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A simple and robust monitoring system for lactate and glucose detection is presented. The system is based on a suitable integrated screen‐printed electrode in thin layer flow cell design (TLFCL) to perform flow injection analysis. The TLFCL is consisted of a two working and one counter electrodes made of carbon and a silver pseudoreference electrode. Both working electrodes (WE) are first modified by graphene nanomaterials. Glucose sensor based on cellobiose dehydrogenase from the ascomycete Corynascus thermophilus (CtCDH) and lactate sensor based on lactate oxidase (LOx) are made on the first and second WE respectively. Both enzymes are entrapped in a photocrosslinkable poly(vinyl alcohol) bearing styrylpyridinium groups (PVA‐SbQ). The electrocatalytic signal of both sensors did not show any cross‐talking, whereas the linear quantification ranges of both glucose and lactate sensors are large enough for wine monitoring.

A sensitive electroanalytical methodology for the determination of uric acid in real samples using adsorptive voltammetry at a multiwalled carbon nanotubes (MWCNT) modified screen printed electrode (SPCE) is presented. Adsorption of uric acid takes place at open circuit potential at an optimized pH 5.0. Studies about the effect of accumulation time and scan rate on the analytical signal were developed and confirm the adsorption nature of the electrodic process. Quantitative analysis of uric acid by using its oxidation process at +0.18 V (vs. an Ag pseudoreference electrode) was carried out with an accumulation time of 5 min. Thus, a linear voltammetric based reproducible determination of uric acid (RSD 5 %) in the range 1–100 µM was obtained. The method was then successfully used for the determination of uric acid in real clinical samples of urine without detection of interferences. The proposed methodology only requires a dilution of the real sample and present advantages as low cost and easy handling for non specialized technicians.