Retention study of inorganic and organic selenium compounds on a silica-based reversed phase column with mixed ion-pairing reagents

Element speciation definitions, analytical methodology, and some examples

This paper gives definitions related to element speciation and the reasons for the need for speciation. The problems focused on, involve sampling, sample preparation and storage, as well as changes in species information that occur during the use of various separation technologies. However, the potential and advantages of the separation methods in element speciation are also discussed. In addition, problems arising during element detection that are attributable to analytes or mobile-phase composition are outlined, as well as the pronounced advantages of detection by inductively coupled plasma-mass spectrometry (ICP-MS). The combination of the various separation systems with element- or molecule-specific detectors creates problems especially in element speciation. These difficulties are described along with recent developments for overcoming them or for improving their coupling efficiency. Finally, several elements for which the issue of speciation is important are discussed, with examples from some recent publications on arsenic, selenium and iodine speciation.

Characterization of selenium species in Brazil nuts by HPLC-ICP-MS and ES-MS

Brazil nuts have been classified as the foodstuffs that contain the highest level of unadulterated selenium, an essential trace element that appears to prevent cancer. To date, characterization of the selenium species in brazil nuts has not yet been investigated. In this work, various sample preparation approaches, including microwave extractions and enzymatic treatments, are examined with the goal of species preservation and subsequent selenium speciation; of these approaches, an enzymatic treatment with Proteinase K proved most effective. High-performance liquid chromatography (HPLC) separation strategies and inductively coupled plasma mass spectrometry (ICP-MS) detection schemes will also be presented. Extracts are evaluated against available standards for the commercially obtainable seleno-amino acids, selenomethionine (SeMet), selenoethionine (SeEt), and selenocystine (SeCys); selenomethionine was demonstrated to be the most abundant of these seleno-amino acids. Further characterization of unidentified selenium-containing peaks is attempted by the employment of several procedures, including electrospray-mass spectrometry (ES-MS). A peptide structure was identified; however, this was considered a tentative proposal due to the large background produced by the extremely complicated brazil nut matrix.