In Situ Generation of Hydrofluoric Acid during Microwave Digestion of Atmospheric Particulate Matter Prior to Trace Element Analysis Using Inductively Coupled Plasma Mass Spectrometry

Pranav Kulkarni, Shankararaman Chellam, Ganesh Ghurye, Matthew P. Fraser

Research output: Contribution to journalArticle

17 Scopus citations

Abstract

Results from a systematic evaluation of numerous microwave-assisted digestion techniques to solubilize trace elements from ambient airborne particulate matter prior to analysis using inductively coupled-plasma mass spectroscopy (ICP-MS) are reported. Direct handling of HF was avoided by generating it in situ in closed Teflon-lined vessels during digestion by heating a mixture of NaF, HNO3, and the sample and later complexing any remaining HF using stoichiometric excess of boric acid. The effects of microwave digestion variables including dwell time (20-120 min), temperature (150-200°C), pressure (38-200 psig), acid type (HNO3 and HF), and absence or presence of peroxide on extraction efficiency were determined. Principal component analysis was conducted on the recoveries of 20 elements (Mg, Al, K, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, As, Rb, Cd, Cs, Ba, La, Pb, and U) from urban particulate matter Standard Reference Material 1648, which revealed that the digestion matrix was the most important variable of all those experimentally investigated. Using H2O2 improved the clarity of the digested sample by ensuring complete oxidation of organic matter thereby facilitating subsequent ICP-MS analysis. Quantitative recoveries of Al, K, Ti, Rb, and La were possible only when using HNO3, NaF (HF), H3BO3, and H2O2, suggesting that these elements were associated with the siliceous matrix of urban airborne particulate matter even though this matrix increased detection limits compared to using HNO3 alone. Even though this method was not suitable for Cr recovery, it was found to extract significantly higher concentrations of Al, Mg, Ni, Co, and Ti from airborne line particulate matter samples obtained in Houston, TX, compared to X-ray fluorescence.

Original languageEnglish (US)
Pages (from-to)517-531
Number of pages15
JournalEnvironmental Engineering Science
Volume20
Issue number6
DOIs
StatePublished - Jan 1 2003
Externally publishedYes

Keywords

  • Fine particulate matter
  • Houston
  • ICP-MS
  • Microwave-assisted digestion
  • Principal component analysis
  • X-ray fluorescence

ASJC Scopus subject areas

  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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