Electrodeposition, stripping analysis

Stripping analysis is a two-step technique. The first or deposition step commonly involves the electrolytic deposition of a small portion of the metal ions in solution into the mercury electrode to preconcentrate the metals. Non-electrolytic (adsorptive) accumulation schemes have also been developed for expanding the scope of stripping analysis to trace metals that cannot be electrodeposited. The preconcentration step is followed by the stripping (measurement) step, which involves the dissolution (stripping) of the deposit. Different versions of stripping analysis can be employed, depending upon the nature of the deposition and measurement steps. 

Anodic stripping voltammetry (ASV) is the oldest, and still the most widely used version of stripping analysis [3]. The technique is applicable to metal ions that can be readily deposited at the working electrode, and particularly for those metals that dissolve in mercury. In this case, the metals are being preconcentrated by electrodeposition into a small-volume mercury electrode (a thin mercury film or a hanging mercury drop). The preconcentration is done by cathodic deposition at a controlled potential and time. The deposition potential is usually ca. 0.3 Y more negative than E° for the least easily reduced metal ion to be determined. The metal ions reach the mercury electrode by diffusion and convection, where they are reduced and concentrated as amalgams ... 

EDTA was determined in waste water by Fayyad et al, who used potentiometric stripping analysis after adding Bi(III) and K C O to the test solution. Uncomplexed Bi(III) was electrodeposited on a mercury film electrode (at -0.4 V vs. SCE) for 50 seconds. The working range was 4.5-95 ppb of EDTA [20]. 

What is the purpose of the electrodeposition step in stripping analysis ... 

Because of its remarkable sensitivity (down to 10-11 M) stripping analysis is the most widely used voltammetric technique for trace metal determination in clinical samples (Wang, 1982A). Stripping analysis can be considered as a two-step technique. In the first step, metals in solution are effectively preconcentrated onto the working electrode by electrodeposition ... 

The purpose of the electrodeposition step in stripping analysis is to preconcentrate the analyte on the surface of the working electrode and to separate it from many interfering species. 

Ham, S., S. Jeon, M. Park et al. 2010. Electrodeposition and stripping analysis of bismuth selenide thin films using combined electrochemical quartz crystal microgravimetry and stripping voltammetry. J. Electroanal. Chem. 638 195-203. 

Sensitivity can be extended by several means. Ultrasonic vibration during electrodeposition lowers the detection limit and enables the analysis of some analytes in difficult matrices.24 In another approach, the detection limit for Fe(III) in seawater is 10 11 M with a catalytic stripping... 

Stripping methods are of prime importance in trace analysis because the electrodeposition step concentrates the analyte and allows minute amounts to be determined with reasonable accuracy. Thus, analytes in the 10 to 10 M range can be determined with stripping methods that use simple and rapid procedures. 

For the detection of inorganic ions, such as Cd, Wang et al. have proposed electropolymerization of p-aminobenzene sulfonic acid [p-ABSA] [113], First, GO is electrochemically reduced to RGO and simultaneously deposited at a constant potential onto a GCE surface. Electrodeposition of poly-ABSA was then carried out voltammetrically in the presence of RGO and the composite film was used for SWASV detection of Cd. Therefore, tin (replacing bismuth or mercury] was electrodeposited on top of the poly(p-ABSA] layer. The composite electrode showed good stripping performance for the analysis of Cd, wider potential window compared to bare GCE and GCE covered with only Sn, and gave a linear response from 1.0 to 70.0 gg L with a detection limit of 0.05 gg L-i. 

Electroless nickel (EN) deposits have been used commercially in many diverse fields, such as the aerospace, automotive, electronics, machinery, oil and gas production and valve industries [20,21]. The detection of nickel in EN deposition baths is very important. The present study includes the analysis of Ni ions based on cathodic stripping of electrogenerated Ni(III) to Ni(II). Initially, the electrodeposition of nickel ions was carried out at -2.0 V under hydrodynamic conditions, and the deposited nickel was converted to Ni(III) (NiOOH) by switching the electrode potential positively to 1.0 V. Under rest conditions, the peak current corresponding to the cathodic stripping of Ni(III) to Ni(II) (Ni(OH)2) was measured. The formed nickel was also removed by electrochemical cleaning in an acidic solution, and thus the electrode could be used for further analyses. 

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