PalmSens

In this report, we describe the application of SPEs to the determination of different contaminants in durum wheat samples. All the reported applications have been developed using PalmSens hand-held potent-iostat equipped with PalmSens PC software for the elaboration of current data (PalmSens, Amsterdam, The Netherlands) (Fig. 29.1). 

Fig. 29.1. Hand-held potentiostat by Palmsens used in all the optimization protocols described in the text.

The different biosensors were obtained using thick-film SPEs produced by Biosensor Laboratory, University of Florence and commercialized by PalmSens. The electrochemical cell, consisting of a graphite working electrode and silver counter and pseudo-reference electrodes, was printed on a planar polyester substrate (Fig. 29.2). 

Fig. 29.3. The Palmsens hand-held potentiostat equipped with the dedicated multiplexer for eight-channel measurements.

The instrumentation consisted of the hand-held potentiostat interfaced with a CH8 multiplexer (PalmSens) (Fig. 29.3) that allow different sensor configuration ... 

The electrochemical procedure was run with the PalmSens electrochemical analysis system, with the software package. All measurements were carried out using the multi-channel system with a Mux acquisition data that allowed to work with eight electrodes in quick succession. 

Palm Instruments BV Ruitercamp 119 3993 BZ Houten The Netherlands www.palmsens.com... 

Potential Functions of the Screen Printed Electrodes (SPEs)/PalmSens Device in the Frame of the WFD with Regard to the Performance Criteria... 

It is used in combination with square wave anodic stripping voltammetry (SWASV) using a PalmSens portable instrument (Palm Instrument BV, Houten, The Netherlands) for the measurement of metals such as Cu (II), Cd (II) and Pb (II) (labile metallic complexes and free metals) in water. These disposable sensors require no calibration for use in the screening mode, so, many samples may be tested for the presence or the absence of metals in water. The quantification can also be performed using the standard addition method in less than 15 min. 

The variation of sensitivity between different sensors was also checked. Calibration curves with five different sensors were performed. A Relative Standard Deviation of 13, 13 and 42% of calibration slopes (sensitivity) were obtained for Cu, Pb and Cd respectively. These variations should have limited consequence on bias and precision when the standard addition method is used. However, for Cd, variations in the limit of quantification between two electrodes could be expected. Finally, the accuracy of the method was evaluated by the measurement of a SWIFT reference material used during the 2nd SWIFT-WFD Proficiency Testing exercise (Table 4.2.2). The reference value was chosen as the consensus value of the selected data population obtained after excluding the outliers. The performances of the device were estimated according to the Z-score (Z) calculation. Based on this score, results obtained with the SPEs/PalmSens method were consistent with those obtained by all methods for Pb and Cu ( Z < 2) while the result was less satisfactory for Cd (2 < Z < 3). 

Table 4.2.2 Summary of performance criteria of the SPEs/PalmSens device...

POTENTIAL FUNCTIONS OF THE SCREEN PRINTED ELECTRODES (SPEs)/PALMSENS DEVICE IN THE FRAME OF THE WFD WITH REGARD TO THE PERFORMANCE CRITERIA... 

This section aims to provide some illustrative examples of how information provided by the SPEs/PalmSens in field conditions can be useful in the frame of the WFD. These results were obtained during field trials organized within the SWIFT-WFD project. The first example highlights the ability of the sensor to assess spatial variability of metal concentration in a river system of average quality conditions. The second one aims to demonstrate how the device can help to assess the temporal variability in case of a simulated accidental metal pollution scenario. 

All metal concentrations found were relatively low and close to the limit of quantification of the SPEs/PalmSens method. As an example, cadmium concentrations estimated by SPEs/PalmSens and ICP/MS are presented in Figure 4.2.3. Although concentrations were over estimated they were in the same order of magnitude as the ICP/MS data. Results obtained by the SPEs/PalmSens are thus semi-quantitative but can lead to a comparison of a sample from one to another. Indeed, this screening resulted in the discrimination of the Oker River from the Aller River leading to the spatial variability assessment of the system. A representative picture of... 

Figure 4.2.3 Cadmium concentrations estimated by SPEs/PalmSens device and ICP/MS on unfiltered samples collected alongside the Alter and Oker rivers...

Field measurements using SPEs/PalmSens device were carried out on unfiltered and filtered at 0.45- im samples and compared with ICP/MS measurements on the... 

Figure 4.2.4 Temporal variability of lead concentrations estimated by SPEs/PalmSens and ICP/MS during the 5-days tank experiments on raw samples...

This study has successfully demonstrated the usefulness of the SPEs/PalmSens device for water monitoring in the frame of the WED through two representative examples. Even if it may not be considered for monitoring at low level of metal concentration (<1 ftg/L), the system is reliable, easy to use, safe, and could be used in a variety of situations to help environmental assessment and control ... 

The results for Cd, Cu and Pb in RM05 and RM12 were obtained with Palmsens - Screen Printed Electrode Voltametric Sensor (Simultaneous determination with square wave anodic stripping voltametry - SWASV) with standard addition... 

Instrumentation Palmsens, portable electrochemical sensor interface, obtained... 

Amperometric measurements in stirred solutions with MWC-NTs-colloidal gold composite biosensors were carried out using a PalmSens Electrochemical Sensor Interface (Palm Instruments BV, Houten, The Netherlands) controlled by a Pocket PC Software. 

Figure 7.24 The wireless PalmSens potentiostat-galvanostat (right) and the pocket PC used to control it (left) (Reproduced by permission of Palm Instruments).

Electrochemical methods are well suited for molecular diagnostics of microorganisms on the genomic and proteomic level. Electrochemical reactions can be designed to produce a direct electronic signal using a portable handheld and inexpensive electrochemical analyzer (AndCare, PalmSens, DropSens etc.) that is commercially available in the market, without any expensive signal transduction equipment [4]. 

Fig. 1.1 Potentiostat Original polarographic analyzer by Heyrovsky (a) Princeton Applied Research Model 164 (b) Radiometer TraceLab PSU unit with the electrode stand (c) AutoLab Model PSTAT (d) handheld device PalmSens (e). Photo (a) reproduced from reference (23) with permission of Prof. Z. Samec, Heyrovsky Institute, Prague, Czech Republic, photos (b-e) by the authors (K. Kalcher and I. Svancara)...

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