Papers by Keyword: Preconcentration

Abstract: A new method for the preconcentration and separation of cobalt ion in water was described. The methodology combines determination using a flame atomic absorption spectrometry (FAAS) with adsorption and desorption of cobalt on the nano-barium-strontium titanate powder coated by dithizone (BST-dithizone). The operation conditions for the pre-concentration and separation of the cobalt, including pH, contact time, eluent condition and co-existing ions have been investigated. The result showed that the cobalt ion could be adsorbed by BST-dithizone. The adsorption quantity was affected by the pH value of medium and shaking time. In the medium of pH 6.0, the adsorption capacity of BST-dithizone to cobalt ion was 8.92 mg·g^-1 when the shaking time was more than10 min. The cobalt adsorbed on the adsorbent could be completely eluated and recovered using 10 g·L⁻¹ ethylene diamine tetraacetic acid (EDTA) solution. The enrichment factor was 100. The detection limit of cobalt was 0.53 ng·L⁻¹. The purposed method has been applied to the pre-concentration and separation of cobalt in the water sample with satisfied results.

Abstract: Zinc ion was adsorbed and enriched by nano-barium-strontium titanate immobilized on aluminum oxide(ABST). The adsorption and elution conditions were investigated. The results showed that ABST had strong adsorption ability for zinc ion in water in the medium at pH more than 4.0. The maximum adsorption capability was up to 16.38 mg/g. The adsorbed zinc on ABST could be eluted and reclaimed with 0.5 mol/L of HNO₃. Zinc was determined by flame atomic absorption spectrophotometry (FAAS). The detection limit of this method for zinc ion was 2.5 μg/L. The method had been applied to the determination of trace zinc in surface water and tap water samples with recovery of 92.5%-98.7%. The results were found to be in agreement with the method of dithizone spectrophotometry.

Abstract: A new system for determination of trace mercury based on separation and preconcentration with porous nano-barium-strontium titanate microspheres (PBSTM) prior to its determination by a hydride generation-atomic absorption spectrometry (HG-AAS) was propounded. The optimum experimental parameters for preconcentration of mercury, such as pH of the sample, contact time, sample volume, eluent and interfering ions, have been studied. The result showed that mercury could be quantitatively retained by PBSTM in the pH range of 4-8, the shaking time was 10 min, and the amount adsorbed was 12.2 mg·g^-1. The mercury adsorbed on the sorbent could be eluated completely with 2 mol·L^-1 HNO₃. The detection limit of this method for mercury was 6.3 ng·L^-1 with an enrichment factor of 60. The method has been applied for the determination of trace amounts of mercury in whole blood and urine with satisfactory results.

Abstract: A new method was proposed for the preconcentration/separation of zinc at trace levels using a modified organo-bentonite with dithizone (D-O-bentonite) and determined by flame atomic absorption spectrometry (FAAS). The influences of some experimental parameters including pH of the sample solution, contact time, and volume of eluent have been investigated. The influences of some matrix elements were also examined. The results show that the zinc ion could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 4-5, the contact time was 20 min, and capacity of adsorption was 32.0 mg·g^-1. The zinc adsorbed on the sorbent could be completely eluated by using 0.5 mol·L^-1 HNO₃. The method has a good tolerance to matrix interference. The detection limit of the method for zinc ion was 0.013 µg·L^-1. The method was successfully applied to the pre-concentration/separation of zinc ion in the tap water and human urine with satisfactory results.

Abstract: A new method for the determination of traces of mercury in environmental and biological samples is described. The present methodology combines determined using a hydride generation-atomic absorption spectrometry (HG-AAS) with pre-concentration/separation of the analyte on dithizone-anchored organobentonite (D-O-bentonite). Optimal experimental conditions for the adsorption of the Hg, including pH, contact time, eluent concentration and volume and co-existing ions have been studied. The result showed that the mercury could be adsorbed on the D-O-bentonite. The adsorbed quantitively was affected by the pH value of medium and contact time. In the medium of pH 5.0, the adsorption time was 15 min, and capacity of adsorption was 23.2 mg·g^-1. The mercury adsorbed on the sorbent could be completely eluated by using 3 mol·L^-1 HCl. The adsorption agent has been applied to the pre-concentration/separation of mercury in surface water and human hair samples with satisfied results.

Abstract: A method for simultaneous determination of trace levels of Cd(II), Cu(II), Pb(II) and Zn(II) in food additives by inductively coupled plasma atomic emission spectrometry ( ICP–AES ) after soluble membrane filter pre-concentration was developed. Based on collection of the chelates of metal ions(II) with 2-(5-bromo-2-pyridylazo)-5- diethylaminophenol ( 5-Br-PADAP ) on soluble membrane filter, the analyte ions were pre-concentrated and separated from sample matrix solutions. Multi-channel membrane filter device and soluble mixed cellulose ester membrane were selected. Analytical parameters such as pH, amount of 5-Br-PADAP, sample volume, etc. were optimized. Under the matrix of Na⁺, K⁺ and Mg²⁺, the limits of detection were 0.02 – 0.03, 0.14 – 0.23, 0.31 – 0.53, 0.10 – 0.15 μg L^-1 for Cd(II), Cu(II), Pb(II) and Zn(II) respectively. The developed method was successfully applied to sodium benzoate, potassium sorbate and basic magnesium carbonate with spiked recoveries of 94% – 115%. Some sample analysis results were checked by inductively coupled plasma mass spectrometry ( ICP–MS ) directly.

Abstract: In last years there is paid a special attention to the analytical chemistry of platinic metals (rhutenium, osmium, platinum, iridium, palladium, rhodium), due to increasing concerns on recovery and recirculation of these metals, especially platinum. In this context, recent data of specialty literature, regarding the approach of new methodological and chemical techniques in platinum metals determination from a variety of complex matrices and wide ranges of concentrations are systematized and briefly discussed.