Square Wave Anodic Stripping Voltammetric Research Articles

Microliter Volume Determination of Cosmetic Mercury with a Partially Crosslinked Poly(4‐vinylpyridine) Modified Screen‐Printed Three‐Electrode Portable Assembly

AbstractWe successfully demonstrated microliter (μL) volume determination of Mercury (Hg) using an in‐built screen‐printed three electrodes containing partially crosslinked poly(4‐vinlylpyridine) (designated as pcPVP) modified carbon‐working, carbon‐counter, and Ag+‐quasireference electrodes (SPE/pcPVP) in a pH 4 acetate buffer solution with 2 M KCl by using the square wave anodic stripping voltammetric (SWASV) technique. Instrumental and solution phase conditions were systematically optimized. Experiments were carried out by simply placing a 500 μL‐droplet of Hg containing real sample mixed with the base electrolyte on the SPE/pcPVP surface. The SPE/Ag+ quasi‐reference system shifted the Hg‐SWASV detection potential ca. 250 mV positive, but the quantitative current values were appreciably similar to that of a standard Ag/AgCl reference electrode. Under optimal condition, the calibration graph is linear in the window of 100–1000 ppb of the Hg droplet system with a detection limit of 69.5 ppb (S/N=3). Finally real sample assays were demonstrated for prohibited cosmetic Hg containing skin‐lightening agents in parallel with ICP‐OES measurements.

Determination of water-soluble and insoluble (dilute-HCl-extractable) fractions of Cd, Pb and Cu in Antarctic aerosol by square wave anodic stripping voltammetry: distribution and summer seasonal evolution at Terra Nova Bay (Victoria Land)

Eight PM10 aerosol samples were collected in the vicinity of the "Mario Zucchelli" Italian Antarctic Station (formerly Terra Nova Bay Station) during the 2000-2001 austral summer using a high-volume sampler and precleaned cellulose filters. The aerosol mass was determined by differential weighing of filters carried out in a clean chemistry laboratory under controlled temperature and humidity. A two-step sequential extraction procedure was used to separate the water-soluble and the insoluble (dilute-HCl-extractable) fractions. Cd, Pb and Cu were determined in the two fractions using an ultrasensitive square wave anodic stripping voltammetric (SWASV) procedure set up for and applied to aerosol samples for the first time. Total extractable metals showed maxima at midsummer for Cd and Pb and a less clear trend for Cu. In particular, particulate metal concentrations ranged as follows: Cd 0.84-9.2 microg g(-1) (average 4.7 microg g(-1)), Pb 13.2-81 microg g(-1) (average 33 microg g(-1)), Cu 126-628 microg g(-1) (average 378 microg g(-1)). In terms of atmospheric concentration, the values were: Cd 0.55-6.3 pg m(-3) (average 3.4 pg m(-3)), Pb 8.7-48 pg m(-3) (average 24 pg m(-3)), Cu 75-365 pg m(-3) (average 266 pg m(-3)). At the beginning of the season the three metals appear widely distributed in the insoluble (HCl-extractable) fraction (higher proportions for Cd and Pb, 90-100%, and lower for Cu, 70-90%) with maxima in the second half of December. The soluble fraction then increases, and at the end of the season Cd and Pb are approximately equidistributed between the two fractions, while for Cu the soluble fraction reaches its maximum level of 36%. Practically negligible contributions are estimated for crustal and sea-spray sources. Low but significant volcanic contributions are estimated for Cd and Pb (approximately 10% and approximately 5%, respectively), while there is an evident although not quantified marine biogenic source, at least for Cd. The estimated natural contributions (possibly including the marine biogenic source) cannot account for the high fractions of the metal contents, particularly for Pb and Cu, and this suggests that pollution from long-range transport is the dominant source.

Voltammetric Determination of Quercetin in Urine at Carbon Paste Electrode

The electrochemical behavior of the quercetin (Q) at a carbon paste electrode (CPE) containing 15% paraffin oil is investigated. Square wave anodic stripping voltammetric (SWASV) was used to determine quercetin in the presence of 0.04 M phosphate buffer (pH ∼4) containing 0.1 M KCl with 15 s accumulation time at 25±1°C. Under the optimal experimental conditions, the adsorbed form is oxidized irreversibly. The linear concentration ranged from 67.66 to 338.3 ppb quercetin. The detection limit of 6.77 ppb Q (r=0.9997), with 15 s accumulation time and the relative standard deviation of 0.45 (n=5) was calculated. The interferences of some metal ions and some amino acids were studied. The method was applied to the analysis of spiked urine, with recovery of 99.9±0.5, and the relative standard deviation of 3.2%. Results were compared with the reported methods.

Measuring mercury ion concentration with a carbon nano tube paste electrode using the cyclic voltammetry method

A simply prepared carbon nano tube paste electrode (CNTPE) was utilized for monitoring mercury ion concentration using the cyclic voltammetry (CV) method and the square wave anodic stripping voltammetric (SWASV) method. The CNTPE was compared with various conventional electrodes. The CNTPE method was applied to determine the concentration of trace levels of Hg(II) in several water samples, which yielded a relative error of 0.6% with a concentration of 0.20 mg L−1 Hg(II). It was deposited at −0.5 V (vs Ag/AgCl), which was subsequently reduced to +0.20 V to strip it on the CNTPE. The optimal experimental conditions for the analysis were found to be as follows: pH value of 4 for the medium; deposition potential of −0.5 V; deposition time of 210 s; SW frequency of 40 Hz; SW amplitude of 100 mV, and step potential of 25 mV. Given these optimum conditions, a linear range was observed within the concentrations of 1.0–25.0 μg L−1 and 40.0–200.0 μg L−1. The detection limit was found to be 0.42 μg L−1.

Electrochemical detection of ascorbic acid (vitamin C) using a glassy carbon electrode.

A method for the detection of ascorbic acid (AA) was developed using square wave anodic stripping voltammetric (SWASV) analysis with a glassy carbon electrode (GCE). The results indicated a sensitive oxidation peak current of AA on the GCE. A linear curve was obtained within a concentration range of 1-130.0 microg/L with a preconcentration time of 270 s. The relative standard deviation of 30.0 microg/L observed was 0.1016% (n = 12) under optimum conditions. The low detection limit (S/N) was pegged at 0.30 microg/L. Results showed that the method developed can be used to assay biological and pharmaceutical samples, and food samples, as well as other materials requiring AA analyses.