Arslan Y. | Yildirim E. | Gholami M. | Bakirdere S.

Review | 2011 | TrAC - Trends in Analytical Chemistry30 ( 4 ) , pp.569 - 585

Speciation studies are much more important than total element determination because toxicity of many elements depends on their chemical forms. Nobody can claim that a foodstuff is very dangerous to eat by determining total arsenic due to the possibility that the arsenic could be present in non-toxic forms. Hence, speciation studies are crucial in any matrix relevant to human beings.Trace-element speciation requires sufficiently sensitive procedures to monitor each species at trace levels. One way to increase the sensitivity for elements forming volatile species is coupling high-performance liquid chromatography (HPLC) with chemical- . . .vapor generation (CVG). This review aims to highlight not only development of HPLC-CVG techniques for ultratrace-elemental speciation in a variety of matrices but also their application. In addition, we discuss the advantages and the disadvantages of these techniques. © 2011 Elsevier Ltd Daha fazlası Daha az

Bakirdere S. | Bramanti E. | D'ulivo A. | Ataman O.Y. | Mester Z.

Article | 2010 | Analytica Chimica Acta680 ( 01.Feb ) , pp.41 - 47

An analytical method was developed for the determination of thiols in biological samples. Reverse phase chromatography coupled to ICP quaduropole MS or Orbitrap MS was employed for the separation and detection of thiols. For the determination of total thiols, oxidized thiols were reduced using dithiothreitol (DTT). Reduction efficiencies for species of interest were found to be close to 100%. Reduced thiols were derivatized by p-hydroxymercuribenzoate (PHMB) and then separated on a C8 column. Optimization of the extraction, separation and detection steps of the HPLC-ICP-MS and HPLC-Orbitrap MS methods was carried out. Detection limi . . .ts for cysteine, homocysteine, selenocysteine, glutathione, selenomethionine and cysteinyl-glycine were found to be 18, 34, 39, 12, 128 and 103fmol, respectively, using HPLC-Orbitrap MS and 730, 1110, 440, 1110 and 580fmol for cysteine, homocysteine, selenocysteine, glutathione, and cysteinyl-glycine using HPLC-ICP-MS. Contrary to expectation, the LODs and RSDs are higher for the HPLC-ICP-MS instrument, therefore HPLC-Orbitrap MS was used for the determination of thiols in yeast samples. Three different brands of baker's yeast and a selenized yeast were analyzed. The GSH and cysteine levels found in these samples ranged from 4.45 to 17.87µmolg-1 and 0.61 to 1.32µmolg-1, respectively. © 2010 Elsevier B.V Daha fazlası Daha az

Güler N. | Maden M. | Bakirdere S. | Ataman O.Y. | Volkan M.

Article | 2011 | Food Chemistry129 ( 4 ) , pp.1793 - 1799

Selenium is one of the trace and essential elements for good health but required only in a very narrow range. Hence, determination of selenium in trace level is important. In this work, cloud point extraction (CPE) with non-ionic surfactant Triton X-114 and the fluorometric ligand, 2,3-diaminonaphtalene (DAN) were used for extraction of trace amounts of organic and inorganic selenium species prior to their determination by spectrofluorometry. CPE parameters affecting complexation and phase separation were optimised. The limit of detection calculated by using nine replicate measurements of 0.020 mg/L Se solution after complexing with . . . DAN and 10-fold CPE preconcentration was 2.1 µg/L. Accuracy of the method was checked using EnviroMat Waste Water, EU-L-2 as CRM and result was found to be in good agreement with the certified value. The suggested method can be used for selenium species of selenite, selenate, and total organic selenium at µg/L level. © 2011 Elsevier Ltd. All rights reserved Daha fazlası Daha az