Abstract
This article has been retracted at the request of the Editors-in-Chief. Please see Elsevier Policy on Article Withdrawal (
http://www.elsevier.com/locate/withdrawalpolicy).
Reason: This article duplicates significant parts of a paper by the same authors that has appeared in
J. Sep. Sci., 28 (2005) 534–542. Furthermore, the last two authors, Roberto Gotti and Vincenza Andrisano, have indicated that they were not involved in the research nor in the preparation or submission of the two papers. One of the conditions of submission of a paper for publication is that authors declare explicitly that the paper is not under consideration for publication elsewhere. Re-use of any data should be appropriately cited. As such this article represents a severe abuse of the scientific publishing system. The scientific community takes a very strong view on this matter and we apologize to readers of the journal that this was not detected during the submission process.