Nafion-coated bismuth film and nafion-coated mercury film electrodes for anodic stripping voltammetry combined on-line with ICP-mass spectrometry

Abstract

Nafion-coated bismuth film electrodes (NCBFEs) and Nafion-coated mercury film electrodes (NCMFEs) were used to electrochemically preconcentrate metal analytes for subsequent analysis by inductively coupled plasma-mass spectrometry (ICP-MS). Either type of electrodes is part of a thin-layer electrochemical flow cell that is positioned upstream of a microconcentric nebulizer for the ICP-MS. Performances of these electrodes were compared in terms of the analytical "figures of merit" (e.g., dynamic ranges, reproducibility, hydrodynamic stability, and elimination of matrix effects detrimental to ICP-MS). The coupled technique (ASV-ICP-MS) is found to possess a wide dynamic range (at least 4 to 5 orders of magnitude) and to be reproducible. Both electrodes are much more stable than the thin mercury film electrode (TMFE) traditionally used for ASV-ICP-MS, with the lifetime of the NCBFE exceeding 8 h. Adopting these electrodes for ASV-ICP-MS overcomes the problems associated with a TMFE, the erosion of which decreases the sample throughput, affects the analysis precision, and contaminates conventional glass nebulizers and spray chambers of the spectrometer. The medium exchange procedure inherent in ASV is successfully implemented with a two-valve flow injection system for the accumulation of trace Cd 2ϩ into the electrode from a certified seawater sample, followed by stripping Cd into a solution that is compatible to the ICP-MS operation. [7][8][9], and studies of electrode reactions involving adsorption/desorption of metals or metal-containing species [10 -12]. Various applications of this combination have been reviewed [1,2]. Earlier work in this field centered on the use of a flow-through electrochemical cell housing a mercurycoated reticulated vitreous carbon (RVC) working electrode [7,[13][14][15][16], and demonstrated that amalgam-forming metal ions (e.g., Cd 2ϩ , Cu 2ϩ , Pb 2ϩ , etc.) could be analyzed with few matrix effects [7]. The elimination of both ICP spectroscopic and nonspectroscopic interferences [17][18][19] resulted from the use of a mediumexchange procedure of ASV [20], in which the flow cell can be thoroughly washed with an interference-free solution (e.g., dilute HNO 3 or high-purity ammonium acetate buffer) before diverting the cell eluent for the subsequent voltammetric scan and ICP-MS analysis. The stripped metals elute in distinct sample plugs and can be easily monitored by time-resolved ICP-MS measurements. Elements whose oxidation states are indistinguishable by ICP-MS (e.g., As(III) and Cr(VI)) have also been deposited onto and stripped off the RVC electrode for subsequent ICP-MS analysis [14,16].In the past ten years or so, efforts were focused on the use of a thin-layer flow cell incorporating a disk electrode [4, 5, 8 -11, 21]. Such a cell was demonstrated to be more advantageous than the flow-through cell, because greater preconcentration efficiency, faster cell clean-up, and smaller sample consumption can all be realized. The thin-layer flow cell design has been successfully utilized b...

A Decade with Bismuth‐Based Electrodes in Electroanalysis

“…In these studies, considerable attention was paid to the testing of Nafion-coated electrodes [75,79,86,87,95] offering the improved selectivity and stability (protection) in both inorganic and organic analysis. Of interest were again "non-film" configurations of the bismuth bulk electrode (BiBE [93] or carbon pastes with dispersed bismuth powder (Bi-CPE [72,96]), and some novel types of micro-electrodes [85,88].…”

“…The implementation of a BiFE for advanced instrumentation was documented using an automatic (robotic) system to monitor continually the release of metal ions during industrial corrosion processes [70]. Interesting was also a combination of ASV/FIA/ICP-MS [95] to analyze on-line nonpretreated samples of seawater.…”

“…Besides determinations of Cd(II) and Pb(II) [72,81,86,87,88,90,95], of interest were the following ions or other inorganic species: Zn(II) [72,78], Tl(I) [72,96], In(III) [72], Sn(II/IV) [74,89], Cu(II) [81], Fe(II/III) [76,00], Mn(II/IV) [72,76], Co(II) and/or Ni(II) [70,85,92], U(VI/V) [73], and newly also Al(III) [82], V(IV/V) [83], Mo(V/VI) [71], and O 2 , S x 2À , S 2 O 3 2À , I…”

Electrochemical Generation of Lead Volatile Species as a Method of Sample Introduction for Lead Determination by Atomic Absorption Spectrometry

“…On the other hand, the electrochemistry combined on-line with atomic spectrometry could further decrease the already remarkable detection levels. More importantly, matrix effects detrimental to atomic spectrometry analysis can also be efficiently eliminated [18][19][20].…”

Ionophore Based Bismuth Film Electrode for Lead

“…These polymeric coatings can improve resistance of the modified electrodes and minimize fouling by surface active compounds existing in samples (Gouveia-Caridade, et al 2006;Hoyer, et al 1987). Among several assessed polymers, Nafion has been widely used (Kefala, and Ecpnomou, 2006;Xu, et al 2008;Cao, et al 2006;Kefala, et al 2004). Nafion is a perfluorosulfonate cationexchange polymer with many ideal properties, i.e.…”