Determination of orthochlorophenol by stripping voltammetry

Abstract

The present work reports on a diflerential pulse and square wave stripping voltammetric procedure for the determination of orthochlorophenol. The best conditions included using 0.1 M KOH solution, an accumulation potential of 0.4 V vs. Ag/AgCl electrode, a square wave amplitude of 60mV, a frlcquency of 50Hz, a step potential of 4mV, and an initial scan potential of -1.OV. Under these conditions, determination limits of ng/rnl were achieved at a stationary glassy carbon electrode. Keywords: Orthochlorophenol, Glassy carbon, Stripping voltammetryOrthochlorophenol is widely used in the pr(oduction of higher chlorinated phenols [I]. It is also used as an intermediate in dyestuffs [2], as a corrosion inhibitor for AJ-Cu alloys [3], in polyester printing [4], and as a preservative [S]. This compound is readily absorbed through the skin in toxic amounts, and is included in the EPA list of priority pollutants. Orthochlorophenol is slightly soluble in water and freely soluble in alcohol, ether, and caustic alkali solutions. A considerable amount of information is available regarding the stability and toxicity of this compound in the environment [6,7]. The LC50 value for orthochlorophenol ranges from 10 to 500 mg/L for aquatics.Techniques The present article reports on a square wave and differential pulse stripping voltammetric procedure for the determination of orthochlorophenol.Orthochlorophenol showed an oxidation peak (Fig. 1) using the glassy carbon electrode, which was irreversible, since there was no cathodic peak. The maximum peak current was obtained in aqueous 0.1 M KOH; in which the cyclic voltammetric peak potential varies linearly with the logarithm of i:he scan rate, i.e., Ep = 0.56 + 0.012 log V (mvjs), the intensity of the peak is ? linear function of the scan rate ( V ) , and i , is proportional to V' for an orthochloryphenol concentration of 10 mM. The current function (ip/ACVF) value increases initially and then decreases in 0.1 M KOH for a scan rate change from 25 mV/s to 250 mV/s. The height of the peak decreases as the sweep cycle increases. This clearly points to adsorption. To confirm ;the results found in the cyclic voltammetry (CV) assays mentioned above, the voltammetric experiments were carried out using the square wave technique, maintaining the amplitude at 25 mV, the step potential at 4mV, and modifying the frequency used. Similar proportionalities were observed. In KOH Ep is directly proportional to the logarithm of the frequency, i.e., Ep = 0.54 + 0.015 log v, and ip is directly proportional to the square root of the frequency. The log ip vs. log V plot yielded a slope of 0.66 in an aqueous alkaline medium.This kind of behavior is associated with diffusion-controlled adsorption in an aqueous alkaline medium, as reported by Osteryoung [ 191. Adsorption of the orthochlorophenol molecule was confirmed by the observation of double potential step chronocoulometric behavior on varying the final potential. The potential of the glassy carbon electrode was stepped from an initial E = 0.0 V t...

Investigation on the Usage of Clay Modified Electrode for the Electrochemical Determination of Some Pollutants

“…This might be due to the electrostatic interaction between the negative nature of electrode at this potential and the radical cation formed because of the elimination of chlorine atom. Compared to previous reports, [19][20][21] lower determination limits are observed with this modified electrode system. A decrease in peak height was observed for accumulation potentials in the negative region.…”

“…In recent years, a number of azo and bis azo dyes have been removed from the list of substances approved for use in foods, drugs, and cosmetics. In continuation to our earlier reports, [19][20][21][22] we describe here the voltammetric behavior of endosulfan (EN), o-chlorophenol (OCP) and direct orange 8 (DO8) using sodium montmorillonite clay modified glassy carbon electrode (NaMM/GCE) in the presence and absence of a surfactant, cetyl trimethyl ammonium bromide (CTAB). The dye, direct orange 8 (Disodium salt of 5-{[4 0 -(1-amino-4-sulfo-2-naphthalenyl)azo]-[(1,1 0 -biphenyl-4-yl)azo]}-2-hydroxybenzoic acid), is a benzidine type dye and is suspected to release harmful amines that are allergenic, carcinogenic or poisonous.…”

“…Figure 1 represents a cyclic voltammogram of endosulfan at GCE and NaMM/GCE. [20] The effect of pH, scan rate and concentration were studied for OCP as in EN. Higher peak current response at pH 1.0 lead to the selection of this pH as the suitable one.…”

Electroanalysis of Endosulfan and o -Chlorophenol in Polypyrrole Coated Glassy Carbon Electrode

“…In continuation to our earlier reports [2,3], we report here the voltammetric and stripping analysis of endosulfan and o-chlorophenol using polypyrrole coated electrode. …”

“…Table III. ELECTROANALYSIS OF ENDOSULFAN 337 FIGURE 7 Calibration graph for endosulfan (OSWSV, Osteryoung square wave stripping voltammetry and DPSV, differential pulse stripping voltammetry) under optimum conditions given in Table II. FIGURE 8 Calibration graph for o-chlorophenol (OSWSV, Osteryoung square wave stripping voltammetry and DPSV, differential pulse stripping voltammetry) under optimum conditions given in Table III. [2,3]. After polypyrrole coating on the electrode, the peak currents decreased in CV and increased in both DPSV and OSWSV techniques.…”