Jump to ContentJump to Main Navigation
Show Summary Details
More options …

American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
Source Normalized Impact per Paper (SNIP) 2017: 1.059

Online
ISSN
1945-3027
See all formats and pricing
More options …
Volume 98, Issue 10

Issues

Amorphous Materials: Properties, structure, and durability. Analysis of H2O in silicate glass using attenuated total reflectance (ATR) micro-FTIR spectroscopy

Jacob B. Lowenstern
  • Corresponding author
  • U.S. Geological Survey, Volcano Science Center, MS 910, 345 Middlefield Road, Menlo Park, California 94025, U.S.A.
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Bradley W. Pitcher
  • U.S. Geological Survey, Volcano Science Center, MS 910, 345 Middlefield Road, Menlo Park, California 94025, U.S.A.
  • College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, U.S.A.
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2015-03-07 | DOI: https://doi.org/10.2138/am.2013.4466

Abstract

We present a calibration for attenuated total reflectance (ATR) micro-FTIR for analysis of H2O in hydrous glass. A Ge ATR accessory was used to measure evanescent wave absorption by H2O within hydrous rhyolite and other standards. Absorbance at 3450 cm-1 (representing total H2O or H2Ot) and 1630 cm-1 (molecular H2O or H2Om) showed high correlation with measured H2O in the glasses as determined by transmission FTIR spectroscopy and manometry.

For rhyolite,

wt%H2O = 245(±9)·A3450 - 0.22(±0.03)

and

wt%H2Om = 235(±11)·A1630 - 0.20(±0.03)

where A3450 and A1630 represent the ATR absorption at the relevant infrared wavelengths. The calibration permits determination of volatiles in singly polished glass samples with spot size down to ~5 μm (for H2Orich samples) and detection limits of ~0.1 wt% H2O. Basaltic, basaltic andesite and dacitic glasses of known H2O concentrations fall along a density-adjusted calibration, indicating that ATR is relatively insensitive to glass composition, at least for calc-alkaline glasses. The following equation allows quantification of H2O in silicate glasses that range in composition from basalt to rhyolite:

wt% H2O = (ω·A3450/ρ) + b

where ω = 550 ± 21, b = -0.19 ± 0.03, ρ = density, in g/cm3, and A3450 is the ATR absorbance at 3450 cm-1.

The ATR micro-FTIR technique is less sensitive than transmission FTIR, but requires only a singly polished sample for quantitative results, thus minimizing time for sample preparation. Compared with specular reflectance, it is more sensitive and better suited for imaging of H2O variations in heterogeneous samples such as melt inclusions. One drawback is that the technique can damage fragile samples and we therefore recommend mounting of unknowns in epoxy prior to polishing. Our calibration should hold for any Ge ATR crystals with the same incident angle (31°). Use of a different crystal type or geometry would require measurement of several H2O-bearing standards to provide a crystal-specific calibration.

Keywords : IR spectroscopy; glass properties; FTIR; water; new technique; igneous petrology; ATR; glass

About the article

Received: 2013-01-14

Accepted: 2013-04-28

Published Online: 2015-03-07

Published in Print: 2013-10-01


Citation Information: American Mineralogist, Volume 98, Issue 10, Pages 1660–1668, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am.2013.4466.

Export Citation

© 2015 by Walter de Gruyter Berlin/Boston.

Comments (0)

Please log in or register to comment.
Log in