Square wave anodic stripping voltammetry SWASV

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. 

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. 

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. 

Table 11. Instrumental parameters for the determination of Hg(II), Cu(II) at GE and Cu(II), Pb(II), Cd(II), Zn(II) at HMDE by Square Wave Anodic Stripping Voltammetry (SWASV). Supporting electrolyte 0.01 mol L EDTA-Na2 + 0.06 mol L ...

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).

SWASV Square wave anodic stripping voltammetry... 

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

---