Experimental factors affecting the phase-selective reversible anodic stripping determination of gallium from 1.0 molar ammonium thiocyanate electrolytes at 60.degree.C and collation of results with sodium thiocyanate/sodium perchlorate-based room temperature measurements

Abstract

The room temperature thiocyanate-catalyzed phase-selective anodic stripping (PSAS) analysis of ultra trace amounts of gallium is not readily extendible to solutions containing organic fragments (e.g., samples of biological origin), and it is further compromised by the unavoidable electrolyte-induced injection of unwanted trace metal contaminants. To circumvent this, a revised approach to gallium PSAS analysis was evaluated which utilizes the recent polarographic discovery that a modest increase in reaction temperature eliminates the conventional need for a corequisite auxiliary salt. The high temperature PSAS peak current response to NaSCN vs. the more preferable NH4SCN electrolyte is discussed, and NH4SCN-based voltammetric results are reported for the effects of temperature, NH4SCN concentration, pH, frequency ( ) and amplitude ( ) of the applied ac signal, and deposition time ( ). The results of PSAS peak current vs. bulk Ga(lll) concentration, peak current reproducibility for 67.8 ppb Ga(lll), and standard addition experiments are tabulated, with the first two compared to accompanying differential pulse anodic stripping (DPAS) measurements on the same solutions. While our 1.0 M NH4SCN PSAS results at 60 °C indicated that Ga can be measured rapidly with fair precision down to 20 ppb, it is necessary to conclude from a comparative evaluation of the influences of , , , and pH for the room temperature vs. high temperature cases that the 60 °C procedure is experimentally somewhat less flexible and, at the present time, probably more suitable to specialized applications.Electroanalytical and electrochemical studies of the catalyzed reversible gallium electrode reaction (GER) have achieved the stage (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) where rapid and inexpensive anodic stripping methods [e.g., phase-selective anodic stripping (PSAS), or differential pulse anodic stripping (DPAS)] can be applied under special conditions for the analysis of samples containing trivalent gallium in the 1 to 10 parts-per-billion (ppb, or ng/g) range. Potentially useful areas for clinical application of these methods for rapid tissue

Adsorptive Cathodic Stripping Voltammetric Method for Determination of Gallium Using an In Situ Plated Lead Film Electrode

“…In trace analysis of gallium, anodic stripping voltammetry (ASV) and adsorptive cathodic stripping voltammetry (AdCSV) are mainly used. The anodic stripping determination of gallium is based on the formation of its amalgam and is carried out mainly on different mercury electrodes 5–10, such as hanging mercury drop electrodes (HMDE) 5–8, stirring mercury electrode 9, renewable mercury film silver based electrode (Hg(Ag)FE) 10, mercury film electrode 11, HgBi thin film electrode 12 and recently on bismuth film electrodes 12, 13. Anodic stripping voltammetry is a potentially attractive approach for trace quantification of gallium, but its main drawback consists in the formation of intermetallic compounds between gallium and zinc, copper, or nickel 4.…”

The advances in electrochemical determination of gallium (III)

“…Meanwhile, different works have reported reversible reduction of Ga(III) in the presence of thiocyanate [13,[15][16][17][22][23][24], which catalyzes reversible electron transfer [16,22]. Reversibility is achieved by heating the solution to 60-80°C, or by using high ionic strength (6 M) [13,[15][16][17][22][23][24]. The first thiocyanate used as supporting electrolyte for polarographic gallium determination was mentioned in works summarized in [15].…”

“…However, these techniques have relatively low sensitivity (n•10 -5 M). Other articles [16,18,[23][24][25][26] have reported the use of anodic stripping voltammetry (ASV) for Ga(III) determination in thiocyanate solution. Pulse modes of ASV, which include phase-selective anodic stripping voltammetry (PSASV), square-wave anodic stripping voltammetry (SW ASV) and differential pulse anodic stripping voltammetry (DP ASV), reduce the residual charging current, and consequently lower concentrations of Ga(III) (10 -9 -10 -7 M) can be detected.…”