Adsorptive stripping voltammetric technique

The adsorptive stripping voltammetric technique led to further improvements of the detection limit of germanium in biological material. By using pyrogallol, the detection limit is 0.1 ng/mL with a standard deviation of 13% [47]. 

Sun N, Mo WM, Shen ZL et al (2005) Adsorptive stripping voltammetric technique for the rapid determination of tobramycin on the hanging mercury electrode. J Pharm Biomed Anal 38 256-262... 

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-... 

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]. 

Adsorptive stripping voltammetry (ASV) is another specialised technique where the SMDE electrode is used for reducible species and carbon paste electrodes for oxidisable ones. This allows enrichment (by factors of 100-1000) of ions at the working electrode before stripping them off for measurement this improves the detection limits. This technique is rapid, sensitive (10 "M), economical and simple for trace analysis. The basic instrumentation for stripping analysis is apotentiostat (with voltammetric analyser), electrode and recorder. While voltammetry is generally very useful for compounds that do not have a chromophore or fluorophore, stripping analysis is the best analytical tool for direct, simultaneous determination of metals of environmental concern, e.g. lead, cadmium, zinc and copper in sea water. 

Adsorptive stripping methods arc quite similar to the anodic and cathodic stripping meilicHls wc have just considered. In this technique, a working electrode is immersed in a stirred solution of the analyte for several minutes. Deposition of the analyte then occurs by physical adsorption on the electrode surface rather than by electrolytic deposition. After sufficient analyte has aceumulared, the stirring is diseonllnued and the deposited material determined by linear scan ot pulsed voltammetric measurements. Quantitative in-lonnation is acquired by calibration with standard solutions that are treated in the same way as samples. 

Kalvoda and Benidakova and Kalvoda have recently reported detection limits of 1 ppb for prometryne and 0.18 ppb for ametryne, repectively, using the adsorptive stripping technique this approach is sensitive but must be combined with a separation step for real applications. The detection limits found by these authors for ametryne were about 10 times higher (cf. Table 7). A swept-potential electrochemical detector, operating in the square wave voltammetric mode is used to detect mixtures of simazine, atrazine, cyanazine, propazine and anilazine after separation on a reverse-phase resin column. The cell used was a jet ceU with a... 

In this study low concentration of timolol are determined by adsorptive stripping voltammetry. The preconcentration of the analyte is done by adsorption of the drug on a surface of the electrode and the adsorbed species are determined by application of a voltammetric scan on the electrode. This technique has recently been employed by different authors for the determination of a number of drugs. 

The adsorption of ions and molecules on the surface of mercury electrodes is a thoroughly investigated phenomenon [51 ]. Surface-active substances are either electroactive [52] or electroinactive [53]. The former can be analyzed by adsorptive stripping voltammetry [54]. This is the common name for several electroanalytical methods based on the adsorptive accumulation of the reactant and the reduction, or oxidation, of the adsorbate by some voltammetric technique, regardless of the mechanisms of the adsorption and the electrode reaction [55, 56]. Frequently, the product of the electrode reaction remains adsorbed to the electrode surface. Hence, the term stripping should not be taken literally in all cases. Besides, some adsorbates may be formed by electrosorption reactions, so that their reduction includes covalently bound mercury atoms. The boundary between adsorption followed by reduction, on the one hand, and electrosorption, on the other, is not strictly defined. Moreover, it is not uncommon that, upon cathodic polarization, the current response is caused by a catalytic evolution of hydrogen, and not by the reduction of the adsorbate itself [57]. However, what is common to all methods is a hnear relationship between the surface concentration of the adsorbate and the concentration of analyte at the electrode surface ... 

In adsorptive stripping voltammetry (AdSV) metal chelates and organic molecules are accumulated by adsorption at the surface of the working electrode. If these compounds are electrochemically active, i.e., if they are reducible or oxidizable. their subsequent voltammetric determination is possible. By this principle of so-called adsorptive stripping voltammetry, organic and organomet-allic compounds are determined in the ultra-trace range. This technique is particularly important for the trace analysis of metals that are not readily deposited as the element on mercury electrodes... 

The concentration of Cu is usually low in food samples, therefore developing sensitive and selective methods for Cu quantification are required. Among the electrochemical techniques, stripping analysis following adsorption accumulation of Cu chelates has demonstrated high sensitivity however after some time of accumulation, metal and chelates may strongly adsorb on the electrode surface. Most of the authors used the standard addition method not only to minimize the food matrix effects, but also to improve the resolution of the voltammetric technique. An ASV procedure at a platinum rotatory disk electrode without the need of Cu-complex formation has been proposed to determine the Cu content of tequila samples [26]. 

Square-wave voltammetry (SWV) is one of the four major voltammetric techniques provided by modern computer-controlled electroanalytical instruments, such as Autolab and pAutolab (both EcoChemie, Utrecht), BAS 100 A (Bioana-lytical Systems) and PAR Model 384 B (Princeton Applied Research) [1], The other three important techniques are single scan and cyclic staircase, pulse and differential pulse voltammetry (see Chap. II.2). All four are either directly applied or after a preconcentration to record the stripping process. The application of SWV boomed in the last decade, firstly because of the widespread use of the instruments mentioned above, secondly because of a well-developed theory, and finally, and most importantly, because of its high sensitivity to surface-confined electrode reactions. Adsorptive stripping SWV is the best electroanalytical method for the determination of electroactive organic molecules that are adsorbed on the electrode surface [2]. 

The adsorption of ions and molecules on the surface of mercury electrodes is a thoroughly investigated phenomenon [51]. Surface-active substances are either electroactive [52], or electroinactive [53]. The former can be analyzed by adsorptive stripping voltammetry [54]. This is the common name for several elec-troanalytical methods based on the adsorptive accumulation of the reactant and the reduction, or oxidation, of the adsorbate by some voltammetric technique. 

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