Kevin C. Honeychurch

Screen-printed electrochemical sensors for monitoring metal pollutants

This review describes current developments in the design and fabrication of disposable screen-printed sensors for the electrochemical determination of trace metals in biological, environmental and industrial samples. Specific emphasis is placed on sensor-fabrication methods, operating details and performance characteristics for selected applications.

Some Recent Designs and Developments of Screen‐Printed Carbon Electrochemical Sensors/Biosensors for Biomedical, Environmental, and Industrial Analyses

Abstract This review describes the design and fabrication of electrochemical sensors/biosensors based on screen‐printing technology and their applications in pharmaceutical, biomedical, environmental, and industrial analyses. Specific emphasis is placed on naturally‐occurring biomolecules, drugs, and potential environmental and industrial pollutants or toxins.

Voltammetric studies of lead at a 1-(2-pyridylazo)-2-naphthol modified screen-printed carbon electrode and its trace determination in water by stripping voltammetry

A method for the trace determination of Pb2+, using a disposable 1-(2-pyridylazo)-2-naphthol (PAN) drop-coated modified screen-printed carbon electrode (PAN-SPCE), has been developed. Lead ions (Pb2+) are accumulated from ammonia buffer, on the PAN-SPCE surface by the formation of a chemical complex at open circuit. The resulting SPCE with complexed Pb2+ is then transferred to 0.1 M HCl and subjected to differential pulse anodic stripping voltammetry. Conditions were optimised with respect to the pH and concentration of the accumulation medium, preconcentration time and the mass of drop-coated PAN. A 5 min preconcentration time resulted in a limit of detection of 15 ng ml(-1). The calibration plot was found bimodal with linear ranges between 0 and 700 ng ml(-1) and 700-5000 ng ml(-1) Pb2+. The principal metal interference was copper, but this problem was successfully overcome by the addition of iodide to the ammonia buffer prior to the accumulation step. The method was evaluated by carrying out lead determinations on spiked potable water samples; the recovery of Pb2+ was 92.5% and the coefficient of variation was found to be 4.4% (n = 5) using a separate PAN-SPCE for each determination. Therefore, the performance data suggests that the method is reliable at the concentrations examined in this study; in addition, the data compared favorably with that obtained by a published method.

Voltammetric behaviour and trace determination of copper at a mercury-free screen-printed carbon electrode.

Screen-printed carbon electrodes (SPCEs), without chemical modification, have been investigated as disposable sensors for the measurement of trace levels of Cu(2+). Cyclic voltammetry was employed to elucidate the electrochemical behaviour of Cu(2+) at these electrodes in a variety of supporting electrolytes. For all of the electrolytes studied the anodic peaks, obtained on the reverse scans, showed that the Cu(2+) had been deposited as a thin layer on the surface of the SPCE. The anodic peak of greatest magnitude was obtained in 0.1 M malonic acid. The possibility of determining Cu(2+) at trace levels using this medium was examined by differential pulse anodic stripping voltammetry (DPASV). The effect of Bi(3+), Cd(2+), Fe(3+), Hg(2)(2+), Pb(2+), Sb(3+) and Zn(2+) on the Cu stripping peak was examined and under the conditions employed, only Hg(2)(2+) was found to significantly effect the response gained. The sensors were evaluated by carrying out Cu(2+) determinations on spiked and unspiked serum and water samples. The mean recovery was found in all cases to be >90% and the performance characteristics indicated the method holds promise for trace Cu(2+) levels by employment of Hg-free SPCEs using DPASV.

Voltammetric Behavior and Trace Determination of Lead at a Mercury‐Free Screen‐Printed Carbon Electrode

Abstract Screen-printed carbon electrodes (SPCEs), without chemical modification, have been investigated as disposable sensors for the measurement of trace levels of Pb. Cyclic voltammetry was employed to elucidate the electrochemical behavior of Pb at these electrodes in a variety of supporting electrolytes. For all of the electrolytes studied the anodic peaks obtained on the reverse scans, showed that the Pb had been deposited as a thin layer on the surface of the SPCE. The anodic peak of greatest magnitude was obtained in 0.1 M HCl. The possibility of determining Pb at trace levels using this medium was examined by anodic stripping voltammetry using the differential pulse waveform in the measurement step. Models are suggested for the deposition of Pb onto the SPCE surface under stated conditions. Calibration plots were found to be linear in the range 6.3 ngmL-1 to 24 ngmL-1 and 24 to 50 ngmL-1; the detection limit was 2.5 ngmL -1 and the coefficient of variation, determined on one single electrode, at a concentration of 12.6 ngmL-1 was calculated to be 2.4 % (n = 5). The effect of copper, cadmium and zinc on the Pb stripping peak was examined and, under the conditions employed, no significant change in current was found. The sensors were evaluated by carrying out Pb determinations on spiked and unspiked pond water. The recovery was calculated to be 97.4 % and the coefficient of variation was 3.2% at a concentration of 12.6 ngmL-1. These performance characteristics indicate that reliable data may be obtained for Pb measurements in natural waters.

Development of an electrochemical assay for 2,6-dinitrotoluene, based on a screen-printed carbon electrode, and its potential application in bioanalysis, occupational and public health.

Screen-printed carbon electrodes (SPCEs) have been successfully exploited as disposable sensors for the measurement of 2,6-dinitrotoluene (2,6-DNT) using a stripping voltammetric method. Initial investigations were undertaken using cyclic voltammetry (CV) to characterise the redox behaviour at the SPCEs. Further studies were then performed to deduce the optimum applied potential and accumulation time for the stripping voltammetric procedure. In addition, a study was carried out to ascertain whether small volumes of samples could be reliably used for analysis. From these studies it was shown that a 100 microl aliquot of sample could be analysed and the calibration plot was linear from 161 ng ml(-1) to 137 microg ml(-1) (R(2)=0.9991), the former concentration being the detection limit. The effects of the major components of human saliva at concentrations normally present were investigated. Of the individual components tested, only Cl(-) and albumen were found to interfere. The presence of the latter could be easily overcome by the addition of (NH(4))(2)SO(4). An interference study was also carried out on some inorganic and organic species that may be present in water samples. The sensors were evaluated by carrying out 2,6-DNT determinations on spiked and unspiked human saliva, dust wipe and potable water samples. Mean recoveries of 47.5, 73.4 and 102.4% were obtained; coefficients of variation of 7.88, 6.63 and 6.42% were calculated for a concentration of 9.1 microg ml(-1) in water, 10.6 microg ml(-1) saliva samples, and 141.1 ng cm(-2) for dust wipe samples, respectively. The performance characteristics show that the method holds promise and reliable data may be obtained for 2,6-DNT in bioanalysis and public health.

Recent Advances in the Fabrication and Application of Screen-Printed Electrochemical (Bio)Sensors Based on Carbon Materials for Biomedical, Agri-Food and Environmental Analyses

This review describes recent advances in the fabrication of electrochemical (bio)sensors based on screen-printing technology involving carbon materials and their application in biomedical, agri-food and environmental analyses. It will focus on the various strategies employed in the fabrication of screen-printed (bio)sensors, together with their performance characteristics; the application of these devices for the measurement of selected naturally occurring biomolecules, environmental pollutants and toxins will be discussed.

The voltammetric behaviour of lead at a microband screen-printed carbon electrode and its determination in acetate leachates from glazed ceramic plates

Microband screen-printed carbon electrodes (μBSPCEs) without further modification have been investigated as disposable sensors for the measurement of lead in acetate leachates from ceramic glazed plates. Cyclic voltammetry was employed to elucidate the electrochemical behaviour of Pb(2+) at these electrodes in a variety of supporting electrolytes. The anodic peaks obtained on the reverse scans, showed that Pb had been deposited as a thin layer on the surface of the μBSPCE. The anodic peak of greatest magnitude was obtained in 0.1M pH 4.1 acetate buffer containing 13 mM Cl(-). The effect of chromium, copper, phosphate, sulphate and tin was examined and under the conditions employed, no significant change in current was found. The μBSPCEs were evaluated by carrying out lead determinations for acetate leachates from glazed ceramic plates. A highly decorated ornamental plate was found to leach 400 μg Pb(2+) (%CV=1.91%). A second plate, designed for dinnerware was found not to leach any detectable levels of Pb(2+). However, once fortified with 2.10 μg of Pb (equivalent to 100 ng/ml in the leachate), a mean recovery of 82.08% (%CV=4.07%) was obtained. The performance characteristics indicate that reliable data has been obtained for this application which could identify potentially toxic sources of lead.

The redox behaviour of diazepam (Valium®) using a disposable screen-printed sensor and its determination in drinks using a novel adsorptive stripping voltammetric assay

In this study we investigated the possibility of applying disposable electrochemical screen-printed carbon sensors for the rapid identification and quantitative determination of diazepam in beverages. This was achieved utilising a previously unreported oxidation peak. The origin of this peak was investigated further by cyclic voltammetry and gas chromatography/mass spectroscopy. At pH 6 the voltammetric behaviour of this oxidation process was found to involve adsorption of the drug allowing for the development of an adsorptive stripping voltammetric assay. Experimental conditions were then optimised for the determination of diazepam in a beverage sample using a medium exchange technique. It was shown that no elaborate extraction procedures were required as the calibration plots obtained in the absence and presence of the beverage were very similar.

The voltammetric behaviour of lead at a hand drawn pencil electrode and its trace determination in water by stripping voltammetry

This is the first reported the proof of concept application of pencil drawn electrodes (PDEs) for anodic stripping voltammetric determination of Pb2+ or any metal ion. PDEs offer advantages of economics, simplicity and rapid fabrication, affording a green alternative for the development of new devices. Cyclic voltammetric investigations of Pb2+ at these electrodes in 0.30 M acetic acid were characterised by a cathodic reduction peak on the initial negative scan resulting from the reduction of Pb2+ ions to Pb0. Anodic peaks obtained on the return positive scan showed that Pb had been deposited as a thin film on the PDE surface. The addition of Cl ions to this electrolyte improved the voltammetric behaviour and a supporting electrolyte of 0.30 M acetic acid containing 0.25 M KCl was found to be optimum. Investigations were made into the possibility of determining trace levels of Pb2+ by differential pulse anodic stripping voltammetry. The effect of accumulation potential and time were investigated and optimised. Three anodic stripping peaks were recorded resulting from the heterogeneous nature of the electrode surface. Using an accumulation potential of 1.1 V and an accumulation time of 200 s a bimodal calibration curve was recorded, with linear ranges between 80 to 330 ng/mL and 330 to 915 ng/mL. The theoretical detection limit (3σ) was calculated as 9.5 ng/mL. Pb2+ determinations on a drainage water sample gave a mean recovery of 100.9 % (%CV= 5.7 %) at a concentration of 166.1 ng/mL indicating the method holds promise for the determination of Pb2+ in such samples.