Heavy metals screen-printed electrodes

On-site Heavy Metal Monitoring Using a Portable Screen-printed Electrode Sensor... 

For chemical monitoring, a list of priority substances has been established that includes metals such as cadmium, lead, and nickel. As far as metals are concerned, voltammetric techniques and more precisely electrochemical stripping analysis has long been recognized as a powerful technique in environmental samples. In particular, anodic stripping voltammetry (ASV) coupled with screen-printed electrodes (SPEs) is a great simplification in the design and operation of on site heavy metal determination in water, for reasons of cost, simplicity, speed, sensitivity, portability and simultaneous multi-analyte capabilities. The wide applications in the field for heavy metal detection were extensively reviewed (Honeychurch and Hart, 2003 Palchetti et al., 2005). 

The aim of this work is to demonstrate how the screen printed electrodes (SPEs) can be used for on site heavy metals monitoring in surface waters in the frame of the WFD. The sensors used consist of mercury-coated screen-printed electrodes coupled with square wave anodic stripping voltammetry (SWASV) (Palchetti et al., 1999). Three metals Cu, Cd, and Pb which are classically analysed in water matrices have been considered. Moreover, Cd and Pb belong to the priority substances list of the WFD. Performance criteria of the device are first established to evaluate the level of confidence of the method. The potential use of the device and its main advantages are then highlighted through two illustrative field applications. 

Since the past decade, different types of sensors and biosensors based on SPE have been prepared in our laboratory, such as a choline sensor with choline oxidase immobilized on the surface of a ruthenized-carbon screen-printed electrode as part of a system for pesticide detection [25], a screen-printed ruthenium dioxide electrode for pFI measurements [26], carbon-modified electrodes with mercury for heavy metals analysis [27], and two kinds of disposable electrochemical DNA biosensors for environmental screening [8-10,15,28,29]. 

Thick-film graphite electrodes can be modified in a similar way to screen printed electrodes to give thick film modified graphite electrodes (TFMGEs). After modifying the surface in different ways the electrodes can be used for the stripping voltammetric determination of a number of heavy metals [46]. 

Metal nanoparticle-doped sol-gel silica nanocomposites do not possess the required conductivity to fabricate bulk or screen-printed electrodes. Inspired by the well-known resorcinol/formaldehyde sol-gel process, which can be pyro-lyzed to get a conductive amorphous carbon matrix, we have synthesized a nanocomposite material made of a carbon xerogel doped with bismuth nanoparticles and fabricated a carbon paste electrode for heavy metal analysis (Figure 46.11) [24]. The resulting sensor is very sensitive to several heavy metals. Extremely low detection limits for Pb " and Cd of around 0.5 ppb were achieved using a nanocomposite paste electrode containing 6 wt. % of bismuth. 

It is commonly assumed that application of these methods in sensors has started from invention of oxygen Clark electrode,2 and in biosensors from first glucose biosensor.3 At present, main sensor application of amperometric and voltammetric detections include, with wide use of oxygen Clark electrode, amperometric sensors based on modification of working electrodes with various materials, and biosensors employing practically all biorecognition species. With the very wide use of the term sensors, applications of voltammetric detections include also miniaturized screen-printed devices for stripping determinations of, e.g., heavy metal ions. 

Chuanuwatanakul S, Pimrat E, Panchompoo J, Chailapakul O, Motomizu S (2008) On-line preconcentratirai and determination of heavy metals by sequential injection-anodic stripping voltammetry by using bismuth film screen-printed carbon electrode. J Flow Injection Anal (Japan) 25 49-52... 

Pauliukaite R, Metelka R, Svancara I, Krolicka A, Bobrowski A, Norkus E, Kalcher K, V) tras K (2004) Screen-printed carbon electrodes bulk-modified with Bi203 or Sb203 for trace determination of some heavy metals. Sci Pap Univ Pardubice A 10 47-58... 

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