Techniques and technologies available for quantification of heavy metals found in water and sediment

Abstract

Sediment serves as a reservoir for heavy metals and therefore, deserves special consideration in the planning and design of aquatic pollution research studies. An undisturbed sediment column contains a historical record of geo chemical characteristi cs. It will allow an investigator to evaluate geo chemical changes over time, and possibly, to establish baseline levels against which current conditions can be compared and contrasted. Metals may be mobilized as a result of natural processes (e.g., weathering and erosion of geo chemical formations) as well as by anthropogenic activity. In the mobilization process, trace elements may be absorbed by days, can complex with organic compounds or may co-precipitate with oxide and hydroxides. Indeed sediment shows a high capacity to accumulate and integrate on time.

Review—Electrochemical Determination of Heavy Metals in Food and Drinking Water Using Electrodes Modified with Ion-Imprinted Polymers

“…The IIP was synthesized (for 24 h) in the presence of Pb(NO 3 ) 2 , 2-(2-aminophenyl)−1H-bencimidazole as ligand, 4-VP as monomer, and EGDMA as crosslinker, respectively. [44][45][46] The surface modification of the GCE electrode was performed with 5 μl of a solution containing 1 mg of IIP-MNPs and 1 ml of DMF. The methodology consisted of a Pb 2+ deposition stage using an imposed potential of −1.2 V for 6 min and a potential scan window from −0.8 V to −0.4 V by DPASV in acetate buffer at pH 5.6, observing the anodic peak current (analytical signal) of the metal around −0.6 V. The modification improved the adsorption capacity and the active surface area which resulted in a high sensibility and selectivity of the electrode towards Pb 2+ , an excellent LOD of 1.5 × 10 −10 mol l −1 and a linear concentration range from 3.0 × 10 −10 mol l −1 to 2.4 × 10 −7 mol l −1 were reported, with a high sensitivity of 7962 μA μmol −1 L. Finally, the authors analyzed fortified fruit juice samples doped with Pb 2+ concentrations of 6.0 × 10 −9 mol l −1 and 3.0 × 10 −8 mol l −1 and obtained an excellent percentage recovery of 95% and a repeatability of 3.9% (%RSD) which also demonstrates the high precision of the measurements.…”

“…In the search for new analytical alternatives, electrochemical techniques have arisen great interest due to their simplicity, easy operation, low analysis times, and speciation capacity by identifying the oxidation status of the element(s) of interest either individually or simultaneously. [44][45][46] Differential pulse voltammetry (DPV) and square wave voltammetry (SWV) are the most commonly used techniques for the highly selective quantification of metal ions and are mainly based on the application of potential pulses over a certain time, measuring the current intensity at the beginning and end of the applied pulse thus eliminating the undesirable non-faradic current, greatly improving the sensitivity of the system. 47 In trace analysis, both techniques can be used in conjunction with anodic stripping (AS) with a first electrodeposition stage to reduce the metal ions on the surface of the working electrode by applying a constant cathodic potential for some time, while in a second stage a potential scan is performed according to the voltammetric pulse technique used, to achieve the analytical signal (anodic peak current intensity) corresponding to the re-oxidation of the metal.…”