SWASV

Anodic-stripping voltaimnetry (ASV) is used for the analysis of cations in solution, particularly to detemiine trace heavy metals. It involves pre-concentrating the metals at the electrode surface by reducmg the dissolved metal species in the sample to the zero oxidation state, where they tend to fomi amalgams with Hg. Subsequently, the potential is swept anodically resulting in the dissolution of tire metal species back into solution at their respective fomial potential values. The detemiination step often utilizes a square-wave scan (SWASV), since it increases the rapidity of tlie analysis, avoiding interference from oxygen in solution, and improves the sensitivity. This teclmique has been shown to enable the simultaneous detemiination of four to six trace metals at concentrations down to fractional parts per billion and has found widespread use in seawater analysis. 

The analytical use of GECE modified in situ by using bismuth solution for square wave anodic stripping voltammetry (SWASV) of heavy metals is also studied [36]. The use of this novel format is a simpler alternative to the use of mercury for analysis of trace levels of heavy metals. The applicability of these new surface-modified GECE to real samples (tap water and soil samples) is presented. 

SWASV measurements were performed using 0.1 and 0.5 M HC1 solutions as electrolytic medium in calibrations for lower concentrations of Pb2+ (from 1 to lOppb), the experimental conditions being the same as for the measurements in acetate buffer. 

The SWASV for zinc was also checked but the results obtained were not satisfactory. According to these results, it can be deduced that zinc competes with bismuth for the surface site rather than involving an alloy formation with this metal as also observed for Bi-GECE studied previously [36]. 

MCPE = magnet carbon paste electrode, SWASV = square wave anodic stripping voltammetry, ASV = anodic stripping voltammetry, PSA = potentiometric stripping analysis, SPEs = screen-printed electrodes, TFGE = thick-film graphite electrode, GCE = glassy carbon electrode. 

Figure 8.3 Schematic representation of copper concentrations relevant to freshwater studies and analytical windows of several analytical techniques. ASV, anodic stripping voltammetry CSV, cathodic stripping voltammetry ISE, ion selective electrode SLM, supported liquid membrane SWASV, square wave anodic stripping voltammetry LC50, lethal concentration for 50% of the population [Cu]t, total metal concentration (adapted from Langford and Gutzman, 1992).

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. 

Figure 4.2.1 (a) (b) Screen-Printed Electrodes (SPEs) (c) (SPEs) in combination with SWASV... 

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 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... 

Table 5.2.5 Results obtained for trace elements by SWASV...

SWASV PT refe- PT unit of SWASV PT reference PT unit of... 

While having slightly higher standard deviation than the state-of-the-art, the SWASV technique proved to be suitable for the determination of the three trace elements in the test sample which contained the target analytes at low fortified concentration level. 

The SWIFT-WFD experience presents cases where SMETs applied in the PT schemes can be considered under control. EEISA and to a certain even Pastel UV are examples. These methods could from now be considered ready to participate in existing and not specifically designed PT schemes. While the limit of detection of SWASV appears to be the main constraint for application to natural matrices, but for the rest this method may also be considered under control. 

Cd DPASV, ETAAS, IDMS, RNAA, SS-ZETAAS, SWASV, ZETAAS... 

SWASV Square wave anodic stripping voltammetry... 

NIES biological CRMs Zn Cd Pb Cu Digest with FlNOs, in a Fligh Pressure Asher [WDCCV] Measure square wave ASV with polarographic analyzer with HMDF [SWASV] [WDCCV- SWASV] Wtirfels 1989... 

For the detection of inorganic ions, such as Cd, Wang et al. have proposed electropolymerization of p-aminobenzene sulfonic acid [p-ABSA] [113], First, GO is electrochemically reduced to RGO and simultaneously deposited at a constant potential onto a GCE surface. Electrodeposition of poly-ABSA was then carried out voltammetrically in the presence of RGO and the composite film was used for SWASV detection of Cd. Therefore, tin (replacing bismuth or mercury] was electrodeposited on top of the poly(p-ABSA] layer. The composite electrode showed good stripping performance for the analysis of Cd, wider potential window compared to bare GCE and GCE covered with only Sn, and gave a linear response from 1.0 to 70.0 gg L with a detection limit of 0.05 gg L-i. 

Tab. 2 Approximate peak heights for SWASV (amplitude of 50 mV, step potential 2 mV and frequency 60 Hz) in a 10% by volume solution of horse blood in 0.1 M nitric acid for a range of pretreatment and deposition stages...

Experimental details Approximate SWASV peak height /pA/... 

The application of power ultrasound to mucus solution extracted from Salmo gairdneri (rainbow trout) into borate buffer followed by SWASV has been shown to directly facilitate a rapid, quantitative... 

Fig. 1 (a) Lead(II) adsorption isotherms onto raw-MWCNTs and po-MWCNTs. Inset plasma modification reactor, (b) Simultaneous measurement of Pb(n) and Cd(II). (c) Sehematie representation of the possible interaetions between heavy metal ions and pn-MWCNTs for sensing metal ions, (d-g) SWASV response of the pn-WMCNTs electrode toward the individual detection of Zn(II), Cd(II) Cu(II), and Hg(II), and at different concentrations in 0.1 M NH4CI/NH3 solution (pH 7.0). The inset in panels d, e, f, and g shows the plot of current as a function of concentration of Zn(II), Cd(II), Cu(II) and Hg(II), respectively. Reprinted with permission from ref 9-11. 

Fig. 3 (a) A schematic drawing of electrochemically selective detection by the PPy-RGO nanocomposite, (b) Typical SWASV stripping signals of Hg " on a PPy-RGO electrode, (c) The voltammetric peak current (background current was subtracted) of other metal ions at the PPy/GCE (dark) and PPy-RGO/GCE (light) in the presence of Zn " ", Cd ", Pb " and Cm" " ions, (d) The illustration of alternative thin mercury-film electrode for ultrahigh sensitive and selective sensing Pb + beyond the selective adsorption of PPy-RGO nanocomposite toward Hg. Reprinted with permission from refs. 17 and 29. 

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