TY - JOUR

T1 - H2O/OH ratio determination in hydrous aluminosilicate glasses by static proton NMR and the effect of chemical shift anisotropy

AU - Riemer, Thomas

AU - Schmidt, Burkhard

AU - Behrens, Harald

AU - Dupree, Ray

N1 - Funding Information: We wish to thank EPSRC for supporting NMR work at Warwick. TR and BS were supported by an EU TMR grant (FMRX-CT96-0064). BS would like to thank Dr. S.C. Kohn and Dr. I. Farnan for discussions and for encouraging this work whilst he was visiting their laboratories. Dr. D. Massiot is also thanked by TR for his encouragement and for technical support.

PY - 2000/4

Y1 - 2000/4

N2 - Static 1H NMR spectra of hydrous NaAlSi3O8 glasses have been acquired at low temperature (140 K) in order to quantitatively determine OH and H2O concentrations. Since both components overlap in the spectra, an unambiguous determination of the line shapes is required. The structurally bonded hydroxyl groups are well described by a Gaussian line and the water molecules exhibit a Pake doublet-like line shape due to the strong proton-proton dipolar interaction. However, at proton resonance frequencies used in this study (360 MHz), the Pake doublet has an asymmetric line shape due to chemical shift anisotropy (CSA), which is significant and must be included in any simulation in order to reproduce the experimental line shape successfully. The simulations for rigid water molecules dissolved in our hydrous aluminosilicate glasses result in a CSA of 30 ± 5 ppm and a dipolar interaction constant of 63.8 ± 2.5 kHz (i.e., dipolar coupling constant (DCC) of 42.6 ± 1.7 kHz), corresponding to a proton-proton distance of rij = 154 ± 2 pm. In contrast to earlier work, water speciation obtained from the simulations of our 1H NMR spectra are in excellent agreement with those obtained from infrared (IR) spectroscopy.

AB - Static 1H NMR spectra of hydrous NaAlSi3O8 glasses have been acquired at low temperature (140 K) in order to quantitatively determine OH and H2O concentrations. Since both components overlap in the spectra, an unambiguous determination of the line shapes is required. The structurally bonded hydroxyl groups are well described by a Gaussian line and the water molecules exhibit a Pake doublet-like line shape due to the strong proton-proton dipolar interaction. However, at proton resonance frequencies used in this study (360 MHz), the Pake doublet has an asymmetric line shape due to chemical shift anisotropy (CSA), which is significant and must be included in any simulation in order to reproduce the experimental line shape successfully. The simulations for rigid water molecules dissolved in our hydrous aluminosilicate glasses result in a CSA of 30 ± 5 ppm and a dipolar interaction constant of 63.8 ± 2.5 kHz (i.e., dipolar coupling constant (DCC) of 42.6 ± 1.7 kHz), corresponding to a proton-proton distance of rij = 154 ± 2 pm. In contrast to earlier work, water speciation obtained from the simulations of our 1H NMR spectra are in excellent agreement with those obtained from infrared (IR) spectroscopy.

KW - Chemical shift anisotropy

KW - Pake doublet

KW - Proton

KW - Static NMR

KW - Water

UR - http://www.scopus.com/inward/record.url?scp=0034164361&partnerID=8YFLogxK

U2 - 10.1016/S0926-2040(99)00059-4

DO - 10.1016/S0926-2040(99)00059-4

M3 - Article

C2 - 10772260

AN - SCOPUS:0034164361

VL - 15

SP - 201

EP - 207

JO - Solid State Nuclear Magnetic Resonance

JF - Solid State Nuclear Magnetic Resonance

SN - 0926-2040

IS - 4

ER -