title: On-line micro column preconcentration system based on amino bimodal mesoporous silica nanoparticles as a novel adsorbent for removal and speciation of chromium (III, VI) in environmental samples.
abstract: BACKGROUND
  Chromium (VI) has toxic and carcinogenic effects. So, determination and speciation of chromium in environmental samples is very important in view of health hazards. In this study, solid phase extraction (SPE) based on bulky amine-functionalized bimodal mesoporous silica nanoparticles (NH2-UVM-7) as a novel nanoadsorbent was applied for preconcentration and speciation of chromium (III, VI) in water samples.
  
  
  METHODS
  UVM-7 was synthesized via atrane route and subsequently functionalized with amino silane via grafting method. In SPE procedure, polymer tubing as a micro-column was filled with NH2-UVM-7 adsorbent. Preconcentration and speciation of Cr (III) and Cr (VI) ions with NH2-UVM-7 were obtained in water samples due to the fact that only Cr (VI) ions can be complexed with-NH2 groups at optimized pH. Finally, chromium concentration was determined by flame atomic absorption spectrometry (F-AAS).
  
  
  RESULTS
  TEM, XRD, and SEM results confirmed the beneficial properties of NH2-UVM-7 as the adsorbent for chromium extraction. Under the optimal conditions, linear calibration curve, detection limit and preconcentration factor were obtained 6-320 μg/ L, 1.2 μg/L and 66.7, respectively (RSD < 5 %). The efficiency of nanoadsorbent for preconcentration and extraction of Cr (VI) was 96 %, whereas it was less than 5 % for Cr (III).
  
  
  CONCLUSIONS
  The developed NH2-UVM7-based SPE/F-AAS method has enough sensitively and simplicity for speciation and determination of Cr (VI) and Cr (III) ions in real water samples. Good recoveries, with low detection limits and good preconcentration factors are the main advantages of this procedure.
authors.affiliation: Occupational and Environmental Health Research Center (OEHRC), Iranian Petroleum Industry Health Research Institute (IPIHRI-PIHO), Tehran, 1485733111 Iran ; Research Institute of Petroleum Industry (RIPI), Tehran, 14665-1137 Iran.
authors.forename: Hamid
authors.initials: H
authors.lastname: Shirkhanloo
authors.affiliation: Department of Chemistry, Semnan University, Semnan, 35131-1911 Iran.
authors.forename: Aisan
authors.initials: A
authors.lastname: Khaligh
authors.affiliation: Occupational Health Engineering Department, School of Public Health, Tehran University of Medical Sciences, Tehran, 6446-14155 Iran.
authors.forename: Farideh
authors.initials: F
authors.lastname: Golbabaei
authors.affiliation: Occupational and Environmental Health Research Center (OEHRC), Iranian Petroleum Industry Health Research Institute (IPIHRI-PIHO), Tehran, 1485733111 Iran.
authors.forename: Zargham
authors.initials: Z
authors.lastname: Sadeghi
authors.affiliation: Research Institute of Petroleum Industry (RIPI), Tehran, 14665-1137 Iran.
authors.forename: Amir
authors.initials: A
authors.lastname: Vahid
authors.affiliation: Research Institute of Petroleum Industry (RIPI), Tehran, 14665-1137 Iran.
authors.forename: Alimorad
authors.initials: A
authors.lastname: Rashidi
keywords: Amine-functionalized UVM-7; Chromium; Flame atomic absorption spectrometry; Removal; Solid phase extraction; Speciation