Stripping voltammetry adsorptive

Stripping Voltammetry One of the most important quantitative voltammetric techniques is stripping voltammetry, which is composed of three related techniques anodic, cathodic, and adsorptive stripping voltammetry. Since anodic strip-... 

In adsorptive stripping voltammetry the deposition step occurs without electrolysis. Instead, the analyte adsorbs to the electrode s surface. During deposition the electrode is maintained at a potential that enhances adsorption. For example, adsorption of a neutral molecule on a Hg drop is enhanced if the electrode is held at -0.4 V versus the SCE, a potential at which the surface charge of mercury is approximately zero. When deposition is complete the potential is scanned in an anodic or cathodic direction depending on whether we wish to oxidize or reduce the analyte. Examples of compounds that have been analyzed by absorptive stripping voltammetry also are listed in Table 11.11. 

DETERMINATION OF RUTIN BY CATHODIC ADSORPTIVE STRIPPING VOLTAMMETRY... 

Besides trace metals, adsorptive stripping voltammetry has been shown to be highly suitable for measuring organic compounds (including cardiac or anticancer drugs, nucleic acids, vitamins, and pesticides) that exhibit surface-active properties. 

Use the adsorption theory (of Section 2-1-3) to explain why adsorptive stripping voltammetry results in nonlinear calibration plots. 

Chloroform extraction of uranium quinoline complex Uranium adsorbed as azide on basic ion exchange column, uranium desorbed with 1 M hydrochloric acid Uranium adsorbed on bismuthol(II) modified anion exchange resin, desorbed with 0.1 M cysteine Uranium, by square wave adsorptive stripping voltammetry... 

Barek et al. have reported on the determination of AT-nitroso compounds, azo compounds, heterocychcs, aromatic nitro compounds, heterocychc amines and even benzyl chloride using electrochemical methods such as voltammetry and polarog-raphy. The nitro and AT-nitroso compounds work particularly well in reductive mode [47, 48]. For appropriate analytes, adsorptive stripping voltammetry and anodic stripping voltammetry can give orders of magnitude lower detection hmits than are available from HPLC with electrochemical detection [48]. 

J. Wang, B.S. Grabaric, Application of adsorptive stripping voltammetry for indirect measurement of nonelectroactive ions using competitive complex formation reactions, Mikrochim. Acta 100 (1990) 31-40. 

Song et al. have reported the determination of chlorpromazine by adsorptive stripping voltammetry [169]. Phosphate buffer saline solution (pH 7.4), consisting of 0.2 g KH2PO4,1.15 g Na2HP04,0.2 g KCl, 8 g NaCl, and 0.047 g MgCl2, was used as the supporting electrolyte. Two methods were reported for the determination of chlorpromazine ... 

The effectiveness of glassy-carbon electrodes coated with cellulose acetate for adsorptive stripping voltammetry was evaluated to alleviate interference from co-adsorbed species [171]. The carbon electrode was coated using a 5% cellulose acetate solution, with the coating being hydrolyzed with 0.07M potassium hydroxide. Repetitive measurements of 1 pM chlorpromazine in the presence of 20 mg/L albumin resulted in peak currents with residual standards of deviation equal to 1.4 and 1.3%, respectively. 

Analytical techniques such as adsorptive stripping voltammetry rely on complex formation to improve detection limits of metals such as V(IV) and V(V) [51]. An example is in the use of cupferron and KBr03 as additives to acidic aqueous solutions, which result in the adsorption of the V(V)-cupferron complex to the electrode surface that catalyzes the reduction of the Br03 ion in solution. This technique has good selectivity over Cu, Pb, Cd, Fe, and Ti, but the response is dependent on pH. 

The Co(II) -phenylthiourea-borax buffer system has been studied applying CSV at HMDE [69]. An irreversible peak observed at —1.5 V was attributed to the catalytic hydrogen evolution. The first reduction step, combined with the adsorptive accumulation of herbicide metribuzin at mercury electrode, has been used for its determination by adsorptive stripping voltammetry [70]. 

Ivanov and Kaplun [76] used catechol in the determination of vanadium by adsorptive stripping voltammetry. It has been shown that the studied electrode process comprised one-electron reversible reduction of vanadium (IV) triscatecholate, previously accumulated at the electrode. It has also been found that the reduced... 

Farias etal. [197] have presented cathodic adsorptive stripping voltammetry of guanine in the presence of copper at static mercury electrode. Cyclic voltammetry was also employed to characterize the interfacial and redox mechanisms. 

Finally, 6-benzylaminopurine has been determined [198] by applying adsorptive stripping voltammetry. 

Recent studies describe the use of cyclic voltammetry in conjunction with controlled-potential coulometry to study the oxidative reaction mechanisms of benzofuran derivatives [115] and bamipine hydrochloride [116]. The use of fast-scan cyclic voltammetry and linear sweep voltammetry to study the reduction kinetic and thermodynamic parameters of cefazolin and cefmetazole has also been described [117]. Determinations of vitamins have been studied with voltammetric techniques, such as differential pulse voltammetry for vitamin D3 with a rotating glassy carbon electrode [118,119], and cyclic voltammetry and square-wave adsorptive stripping voltammetry for vitamin K3 (menadione) [120]. 

Stripping voltammetry has also been applied to the quantitation of the drug in formulations. A sensitive and precise method using square-wave adsorptive stripping voltammetry has been developed for the determination of sulpha-quinoxaline in veterinary formulations [157]. The differential pulse adsorptive stripping voltammetric determination of midazolam in injectable formulations as a method for quality control has been demonstrated [158]. 

The majority of the works with HgCFMEs focused on the anodic stripping of metals [127]. However, our works have been mainly focused on the determination of organic molecules that show the ability of adsorption on mercury [119-121], for example pteridines. Therefore, those molecules can be primarily preconcentrated on HgCFMEs and, subsequently, determined by cathodic stripping techniques. This procedure is described like adsorptive stripping voltammetry and it is a very interesting technique for trace and ultratrace analysis due to its... 

Fig. 32.6. (a) Optimisation of the thin mercury film in terms of f mm using d.c. adsorptive stripping voltammetry of 5.0 x 10-8M aminopterin in pH 5 acetate buffer. Mercury salt solution = 1.0 x 10 3M in 0.5M HC1 tm — 60s Eacc — 0.0V, tacc. = 60s film was stripped anodically at lOOmV/s. (b) Optimisation of the thin mercury film in terms of film using d.c. adsorptive stripping voltammetry of aminopterin. Emm — -0.8 V. Rest of conditions as in (a), (c) Optimisation of the thin mercury film in terms of film versus a.c. stripping voltammetry of aminopterin 5 x 10 9M. Rest of the conditions as above, (d) Two anodic stripping peaks of the thin mercury film under optimum deposition conditions tmm = 90s Emm = -0.8V scan rate = lOOmV/s. 

Microfluidic chip devices are also shown to be attractive platforms for performing microscale voltammetric analysis and for integrating voltammetric procedures (linear-sweep, square-wave and adsorptive-stripping voltammetry) with on-chip chemical reactions and fluid manipulations [97]. 

Abollino, O., Mentasti, E., Sarzanini, C., Porta, V and van den Berg, C.M.G. (1991) Speciation of iron in antarctic lake water by adsorptive stripping voltammetry. Anal. Proc., 28, 72-73. 

Bobrowski, A., B. Bas, J. Dominik, et al. 2004. Chromium speciation study in polluted waters using catalytic adsorptive stripping voltammetry and tangential flow filtration. Talanta 63 1003-1012. 

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