Analytica Chimica Acta 530 (2005) 61–67 Miniaturised stripping-based carbon modified sensor for in field analysis of heavy metals Ilaria Palchetti ∗ , Serena Laschi, Marco Mascini Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, FI, Italy Received 4 June 2004; received in revised form 16 August 2004; accepted 16 August 2004 Available online 7 December 2004 Abstract A new miniaturised electrochemical carbon modified sensor for on-site stripping analysis of trace heavy metals is described. The graphite working electrode is modified with a cellulose-derivative mercury coating. A detailed description of the construction of the system as well as the systematic laboratory test carried out to optimise its performance is reported. Coupling this sensor with square wave (SW) anodic stripping analysis, detection limits of 0.3, 1 and 0.5 gl -1 were found for lead(II), cadmium(II) and copper(II), respectively. Deoxygenation of sample solution is not required. The entire analysis time is shorter than 4 min. Examples of on-site environmental applications are given. In particular, on-site analysis of heavy metals was performed at a contaminated site. For this purpose, the sensor was coupled with a portable commercial electroanalytical instrumentation. © 2004 Elsevier B.V. All rights reserved. Keywords: Stripping voltammetry; Screen-printed electrodes; Mercury-coating; Heavy metals; On-site analysis; Soil; Sediments; Wastewater 1. Introduction Stripping analysis is considered to be the most sensitive electroanalytical technique and to be highly suitable for the task of field monitoring of toxic metals. The sensitivity of stripping analysis is attributed to its preconcentration step, in which trace metals are accumulated onto the working elec- trode surface [1,2]. This is then followed by the measurement step, in which the metals are stripped away from the electrode during an appropriate potential scan. Stripping analysis can provide useful information on the total metal content, as well as characterisation of its chemical forms (e.g. labile fraction, etc.) [3]. Various advances in stripping analysis should accelerate the realisation of on-site environmental testing of toxic met- als. New sensor technology has thus replaced the traditional laboratory-based mercury electrodes and associated cum- bersome applications (oxygen removal, cell cleaning, etc.) ∗ Corresponding author. Tel.: +39 0554573323; fax: +39 0554573397. E-mail address: ilaria.palchetti@unifi.it (I. Palchetti). [4–11]. Portable and compact (hand-held) battery operated stripping analysers are currently being commercialised for controlling these field-deployable devices [5,12]. As reported in literature [4], the use of screen-printed elec- trodes (SPE) is a great simplification in the design and oper- ation of heavy metal determination, in accordance with the requirements of a decentralised assay. Screen-printed elec- trodes are miniaturised devices, based on different layers of inks printed on an inert plastic or ceramic substrate. More- over, since they are mass-produced at low cost, they can be used as disposable. Applications of these devices in the field of heavy metal detection are extensively reviewed in [11,13]. In this paper, the use of mercury-coated screen-printed sensors, prepared beforehand in the lab and ready to use on-site, is proposed. In this way, the handling, the trans- port and disposal of toxic mercury(II) solutions during de- centralised measurements is avoided, since the coating is pre-deposited on the electrode surface. Similar approaches have been reported in literature: a Nafion ® -mercury acetate membrane cast onto a glassy carbon electrode coupled with classical bulky reference and counter electrodes is reported in 0003-2670/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aca.2004.08.065