title: Improved method for measurement of multi-walled carbon nanotubes in rat lung.
abstract: BACKGROUND
  Previously, we have developed and reported the method of measuring multi-walled carbon nanotube (MWCNT) in the lung from rats exposed to MWCNT intratracheally. The present research was performed to improve the analytical method of MWCNT to measure multiple samples in a short period of time. For the xanalysis of MWCNTs from tissues, the existence of carbon black may interfere. Therefore, it was examined whether or not carbon black interfere the determination of MWCNT in the standard solutions. Then, MWCNTs were administered to rats and the MWCNTs were determined in the rats by the new method and the recovery rates and time for determination were calculated. The standard solutions for MWCNTs and carbon black were prepared, and the concentrations in the solutions were determined by HPLC with checking their linearity between the concentrations and signal intensities. The reproducibility of the determination was also checked.
  
  
  METHODS
  The concentrations of MWCMTs in the standard solutions were determined by HPLC with a fluorescent detector. Those of carbon black were also determined using the same method. The MWCNTs were administered to rats intratracheally. The MWCNTs in the lung were determined in a newly modified method including digestion of lung tissues by strong alkali solution and marking MWCNTs by benzo[ghi]perylene. The time for the determinations was recorded and the recovery rate of MWVNTs was calculated.
  
  
  RESULTS
  MWCNT showed linearity in a range of 0.2 to 1.0 μg/mL. In contrast, carbon black demonstrated a very low slope, showing flat pattern. Regarding the reproducibility of the analysis, the coefficient of variation was lower than 10 %. The analysis of 20 samples were completed in 1.5 h. The recovery rates of MWCNT from the lung of rats receiving intratracheal MWCNT administration were 101 to 102 %.
  
  
  CONCLUSIONS
  The improved method for measuring MWCNT allows an efficient MWCNT quantitation in a short period of time. Also, a small amount of MWCNTs can be measured without influence of carbon black.
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ohnishi
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yamamoto
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Kasai
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kano
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Senoh
authors.affiliation: Occupational Health Research and Development Center, Japan Industrial Safety and Health Association, 5-35-1 Shiba, Minato-ku, Tokyo, 108-0014 Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Higashikubo
authors.affiliation: Occupational Health Research and Development Center, Japan Industrial Safety and Health Association, 5-35-1 Shiba, Minato-ku, Tokyo, 108-0014 Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Araki
authors.affiliation: Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015 Japan.
authors.forename: Shoji
authors.initials: S
authors.lastname: Fukushima
keywords: Benzo[ghi]perylene; Carbon black; HPLC; Improved method; Intratracheally; Lungs; Multi-walled carbon nanotubes; Quantitation; Rats; Validation