title: Solid phase extraction of Co ions using L-tyrosine immobilized on multiwall carbon nanotubes.
abstract: A study was performed to assess the performance of aminoacids immobilized on carbon nanotubes (CNTs) for their employment as a sorbent for solid phase extraction systems. An immobilization method is introduced and the aminoacid L-tyrosine was chosen as a case study. A spectrophotometric study revealed the amount of aminoacid immobilizated on CNTs surface, and it turned to be of 3174 micromol of L-tyrg(-1). The material was tested for Co retention using a minicolumn inserted in a flow system. At pH 7.0, the amount of Co retained by the column was of 37.58+/-3.06 micromol Co g(-1) of CNTs. A 10% (v/v) HNO(3) solution was chosen as eluent. The pH study revealed that Co binding increased at elevated pH values. The calculation of the mol ratio (moles of Co bound at pH 9 to moles of l-tyr) turned to be 3:1. The retention capacity was compared to other bivalent cations and showed the following tendency: Cu(2+)>Ni(2+)>Zn(2+)>>Co(2+). The analytical performance was evaluated and an enrichment factor of 180 was obtained when 10 mL of 11.37 microg L(-1)Co solution was loaded onto the column at pH 9.0; reaching a limit of detection (LoD) of 50 ng L(-1). The proposed system was successfully applied to Co determination in QC-LL2 standard reference material (metals in natural water).
authors: Instituto de Química de San Luis (INQUISAL-CONICET), Chacabuco y Pedernera, CP 5700, San Luis, Argentina.
authors: Pablo H
authors: PH
authors: Pacheco
authors: Patricia
authors: P
authors: Smichowski
authors: Griselda
authors: G
authors: Polla
authors: Luis D
authors: LD
authors: Martinez
mesh_terms: D000327:Adsorption; D003035:Cobalt / Q000302:isolation & purification*; D005618:Fresh Water / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000302:isolation & purification; D037742:Nanotubes, Carbon; D012015:Reference Standards; D052616:Solid Phase Extraction / Q000379:methods*; D014443:Tyrosine
chemical_list: D007477:Ions; D037742:Nanotubes, Carbon; D003035:Cobalt; D014443:Tyrosine