University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Website: @unf

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Classification: Geological -> ore -> leachate

Citations 4

"A Robust Multi-syringe System For Process Flow Analysis. Part 3. Time Based Injection Applied To The Spectrophotometric Determination Of Nickel(II) And Iron Speciation"
Analyst 2001 Volume 126, Issue 6 Pages 903-910
Fernando Albertús, Andreu Cladera, Eduardo Becerra and Victor Cerdà

Abstract: A new software-controlled time-based system for sample or reagent introduction in process flow injection analysis was developed. By using a multi-syringe burette coupled with one multi-port selection valve, the time-based injection of precise known volumes was accomplished. Characteristics and performance of the injection system were studied by injecting an indicator in a buffered carrier. Two multi-syringe time-based injection (MS-TBI) systems were implemented: first, the injection of a sample in a multiple-channel manifold where the sample would sequentially merge and react with different reagents, and second, the sequential injection of several solutions (sample and reagents) into a particular flowing stream. The first system was applied to the spectrophotometric determination of nickel(ii) in diluted samples from the acidic nickel ore leaching process, by using ammonium citrate as carrier, a saturated solution of iodine as oxidizing agent and alkaline dimethylglyoxime as chromogenic reagent. The sampling frequency attained was 57 h-1. Determinations on process samples compared well at the 95% confidence level with the reference values obtained by ICP-OES. The second time-based injection system was applied to the speciation of iron. Total iron and iron(ii) concentrations were separately and sequentially determined using 1,10-phenanthroline in acetic buffer medium as reagent. The developed manifold allowed the optional use of two different carrier solutions, containing or not containing ascorbic acid, for performing the separate determinations. Also, in the sequential procedure, plugs of reducing carrier were alternatively intercalated before the sample injections used for total iron determinations. Sampling frequencies of 68 injections per hour were routinely used. Accuracy was assessed by analyzing synthetic known mixtures of Fe(iii) and Fe(ii) standard solutions. Recoveries of 98-100.5% with a maximum relative standard deviation of 3.6% were found. Results obtained for various samples of fertilizers agreed well with those attained by the standard batch procedure.
Nickel(II) Spectrophotometry Multisyringe Timed injection Method comparison Computer

"Determination Of Uranium Using A Flow System With Reagent Injection. Application To The Determination Of Uranium In Ore Leachates"
Anal. Chim. Acta 1990 Volume 230, Issue 1 Pages 217-220
J. L. Perez Pavon, B. Moreno Cordero, E. Rodriguez Garcia and Hernandez Mendez

Abstract: A flow injection spectrophotometric system is described in which UO22+ in the sample stream is reduced by passage through a glass column (5 cm x 2 mm) packed with Pb powder (0.1 to 0.3 mm) to U(IV), which then reacts with an injection of 0.2 mM arsenazo III in 3.6 M HCl containing 1% of Triton X-100 to form a complex for absorbance measurement at 665 nm. The detection limit is 26 nM-U, and the coefficient of variation (n = 10) at 6 µM was 0.62%. Zirconium can be masked with oxalic acid, and of 19 other species tested only Th interferes; this interference can be overcome by incorporating a valve to by-pass the reducing column and measuring the difference in peak heights with and without reduction.
Uranium Column Preconcentration Glass Detection limit Interferences Valve Reduction column Triton X Reverse Surfactant

"Fully Automatic Flow Injection System For Determination Of Uranium At Trace Levels In Ore Leachates"
Analyst 1983 Volume 108, Issue 1285 Pages 470-476
Thomas P. Lynch, Arthur F. Taylor and John N. Wilson

Abstract: An automatic flow injection system is described for the determination of uranium in ore leachates. Following injection from an autosampler, the leachate is extracted with a solution of tributyl phosphate in heptane, which removes uranium, and the organic phase is separated. The extract is reacted with an ethanolic solution of 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol (BrPADAP) and benzyldimethyltetradecylammonium chloride (zephiramine) and the resulting ternary complex with U(VI) is measured spectrophotometrically at 579 nm. The lower limit of determination is 0.1 p.p.m. of uranium and up to 50 samples per hour can be analyzed. In terms of speed and sensitivity this improves significantly on published procedures using segmented flow systems. The technique is ideal for process control and can be applied to the analysis of ores following mineralisation.
Uranium Spectrophotometry Sample preparation Solvent extraction

"Determination Of Free Cyanide In Mineral Leachates"
Analyst 1984 Volume 109, Issue 4 Pages 421-423
Thomas P. Lynch

Abstract: In this rapid, specific and precise method, an automatic flow injection system is used for determining free CN- in samples from ore-leaching processes. After injection into a carrier stream (NaOH), the sample is mixed with a stream of NaOH - KCN solution, and CN- are determined with use of an Orion 90-06 electrode. The range of the method is 10 to 1000 ppm and samples can be processed at 120 h-1. Recoveries are similar to those of a titrimetric method. Sulfide interferes and, at 10 µM CN-, the max. tolerable levels of Cl-, Br- and I- are 10 M, 0.05 M and 1 µM, respectively. The system is robust and reliable, sample contamination is minimized and release of gaseous HCN to the atmosphere is virtually eliminated.
Cyanide, free Electrode Interferences