Abstract: A study was made to investigate the feasibility of using an anion-exchange resin for on-line separation of trace amounts of niobium, tantalum, tungsten, zirconium and hafnium from iron matrix samples. The incorporation of a micro-column packed with Dowex 1X8-100 ion-exchange resin into a flow injection system is presented. The detection was done with inductively coupled plasma mass spectrometry (ICP-MS). The sample treatment, optimization of analytical variables and measurable concentration levels are discussed. Recoveries from standard additions to a high-purity iron were for all the analytes close to 100%, with relative standard deviations ranging from 0.7 to 3.0%. The limits of quantification (10 sn-1) calculated from a 5% (m/v) iron sample solution were 8, 5, 14, 12 and 10 ng g-1 for Nb, Ta, W, Zr and Hf, respectively. The accuracy of the proposed method was tested by determining these elements in Euronorm-CRM 098-1 reference material. Recoveries from 0.250 g test portions of the above reference material spiked with 2.5 and with 12.5 ng each of the five analytes are reported.

Abstract: Ni(II) and Co(II) were determined simultaneously by adsorptive cathodic stripping voltammetry (AdCSV) in a computerized flow injection system. The working electrode was a glassy C disk that was fitted in a wall-jet flow cell. The electrode was initially electrochemically coated with a Hg film at -1.0 V by injecting a Hg(II) solution in the flow stream. Then, the sample, containing Ni(II) and Co(II), was mixed online with a solution containing dimethylglyoxime (DMG) at pH 9 to selectively complex the metal ions and was injected in the flow system. After a number of successive injections during which accumulation took place under controlled potentiostatic conditions, the surface-bound complexes were reduced in NH3 buffer at pH 9 by a cathodic scan of the potential of the working electrode in the square wave mode and the current-potential response was recorded. Finally, the electrode surface was regenerated by a potentiostatic polarization at -1.4 V in the same buffer. The app. could be easily converted for continuous-flow accumulation to increase the sensitivity; in this mode of operation, instead of performing discrete injections, the sample was continuously pumped through the cell. Various parameters associated with the pre-concentration, stripping and regeneration steps were optimized for the determination of Ni(II) and Co(II). The selectivity of the method was demonstrated for the anal. of high purity Fe; the accuracy for the determination of Ni(II) and Co(II) was 11 and 3%, respectively while the coefficient of variation was 10 and 8%, respectively.

Abstract: The sample was dissolved in HNO3 - HCl (1:1) and the solution was passed through a column of activated acidic alumina 90 to enrich the SO42- (eluted with aqueous 2 mM NH3) and remove the Fe. The standard-addition method was used. The limit of detection was 0.3 ppm. Flow injection systems were combined with an inductively coupled plasma atomic emission spectrometer for the development of online enrichment and determination of trace amounts of S in high-purity iron samples (obtained as Certified Reference Materials from the Iron and Steel Institute of Japan). An alumina microcolumn was used for the enrichment of sulfate and the removal of Fe. The properties of several types of alumina were compared. The effects of Fe, diverse elements and acids on the adsorption of sulfate were investigated. The detection limit (3s) of S in high-purity iron is 0.3 µg g-1. A standard additions method and 2 online standard addition methods were used for the determination The possibility of S vaporization at the trace amt. level is evaluated.