As(III) Determination in the Presence of Pb(II) by Differential Alternative Pulses Voltammetry

Abstract

Differential Alternative Pulses Voltammetry (DAPV), introduced by the authors earlier, was applied with HMDE for direct As(III) determination in the presence of Pb(II) in natural water without sample pretreatment. Distinguishable peaks of As(III) and Pb(II) were registered in 1 M HCl supporting electrolyte at a concentration ratio as high as 1 : 6, while complete peak overlapping occurs applying DPP at any concentration ratio at the same experimental conditions. In-situ As(III) determinations in the presence of Pb(II) in contaminated ground waters in Mexico were performed, using especially designed disposable safe mercury drop electrodes.Keywords: As(III) determination, Differential alternative pulses voltammetry (DAPV), Safe disposable mercury drop electrode, Arsenic DOI: 10.1002/elan.201000090 As(III) and As(V) are among the arsenic species, usually present in the arsenic polluted natural ground and underground waters resulting from the natural processes and the industrial activity of the ore-extracting and mineral processing plants [1 -6]. As(III) is a carcinogenic environmental pollutant, about 10 times more toxic than As(V) [7]. Its limit in drinking water was set by EPA to 10 mg/L. Arsenic contaminated waters often contain other impurities as well and the toxic Pb(II) is frequently one of them [8].The high As(III) toxicity makes the arsenic speciation of a great importance for the ecological expertise. However, reliable As(III) quantification is possible only in situ because of the rapid As(III) oxidation to As(V) by the dissolved oxygen, a process catalyzed by Fe salts [9 -13]. The As(III) oxidation favored by the low pH required by the sample conservation procedures affects the arsenic species equilibrium, thus corrupting the water toxicity results.While the spectral methods as AAS and ICP [14 -19] can not be applied for in situ determinations, the voltammetric techniques as differential pulse polarography (DPP) [20] are suitable for this purpose. They allow the direct in field quantification of As(III) and its distinction from As(V) which is not electrochemically active [21 -24]. A number of authors [2, 19, 25 -35] [32, 42 -44].Acids as 1 M HCl, 1 M H 2 SO 4 , 1 M HClO 4 , 1 M HNO 3 , 1 M H 3 PO 4 , 1 M CH 3 COOH, 1 M tartaric acid, 1 M oxalic acid, etc. were mostly reported as supporting electrolytes for As(III) determination, as well as combined with salts or triton X-100 [45]. The lowest LOD achieved by DPP in 1 M HCl was 0.3 ppb As(III) [25]. However, differential pulse anodic stripping voltammetry (DPASV) application allows attaining a LOD as low as 0.02 ppb, as reported by Forsberg et al. [45].Species as Pb(II), Sn(II), Tl(I), Bi(III), Sb(III), and selenite having E 1/2 close to that of As(III) interfere the As(III) determination causing overlapping of its peak [46]. In 1 M HCl, the most commonly applied supporting electrolyte, the presence of Pb(II) causes complete overlapping of the As(III) peak as shown bellow, thus requiring the application of complicated laboratory sample pretr...

Diazirine‐functionalized Nanostructured Platform for Enzymes Photografting and Electrochemical Biosensing

“…As the DAPV principle was discussed by the authors earlier [30][31][32][33][34], only a brief description is presented below. The conventional differential pulse voltammetry (DPV) is based on superimposition of a rectangular pulse with a fixed amplitude ΔE and width on the scanned dc potential, one pulse for every potential repetitive cycle which includes scan step, delay time, and pulse.…”

“…This advanced technique, introduced by Zlatev [24], combines the high resolution of the second order voltammetric methods as Radio-Frequency Polarography [25,26], Second Harmonic AC Voltammetry [27], and Differential Faradaic Rectification Polarography [28] with the high sensitivity and instrumental simplicity of the differential pulse voltammetry [29]. DAPV has been successfully applied for the simultaneous determination of a range of inorganic and organic species [30][31][32][33][34].…”

Application of Anodic Stripping Differential Alternative Pulses Voltammetry for Simultaneous Species Quantification

“…The second order voltammetric techniques such as Radio Frequency Polarography (RFP) , Differential Faradaic Rectification Polarography (DFRP) , and Differential Alternative Pulses Voltammetry (DAPV) are based on the “electrochemical derivation” of the electrochemical systems I/E characteristics resulting from bipolar potential deviations with small amplitudes (anodic and cathodic rectangular or sinusoidal pulses imposing). Due to the nonlinearity of the I−E characteristics[1, 11, 14, 15] voltammograms shaped as second derivative of the voltammetric wave are registered for any of the quantified species as pair of anodic and cathodic peaks having small half‐widths.…”

“… and applied for simultaneous quantification of species having close E 1/2 . . DAPV combines the simplicity and the high sensitivity of the Differential Pulse Voltammetry (DPV) with the high resolution of the second order voltammetric techniques.…”

Resolution of a Mononitrophenol Isomers Mixture by Differential Alternative Pulses Voltammetry

“… provides the great resolution of the second order voltammetric techniques, as Radio‐Frequency Polarography , Second Harmonic AC Voltammetry , and Differential Faradaic Rectification Polarography , in combination with the high sensitivity, precision, and instrumental and operational simplicity of the most common voltammetric technique, the differential pulse voltammetry (DPV). DAPV has been successfully applied for the simultaneous determination of a range of inorganic species with close E 1/2 potentials , as well as for the resolution of the dihydroxybenzene isomers mixtures .…”