TY - JOUR
T1 - UWG-2, a garnet standard for oxygen isotope ratios
T2 - Strategies for high precision and accuracy with laser heating
AU - Valley, John W.
AU - Kitchen, Nami
AU - Kohn, Matthew J.
AU - Niendorf, Christopher R.
AU - Spicuzza, Michael J.
PY - 1995/12
Y1 - 1995/12
N2 - UWG-2 is a new garnet standard for oxygen isotope analysis prepared from a single large porphyroblast that was homogeneous (±0.21‰) at the millimeter-scale before grinding. The δ 18O value of UWG-2 has been determined in seven laboratories using either a laser probe system or externally heated Ni reaction vessels. The raw laser probe value is 5.74‰ at the University of Wisconsin. If all data are normalized to NBS-28 = 9.59‰, then the UW value (5.89‰) is in good agreement with the average of all labs (5.78‰). There is no significant difference between garnet analyses made with the two techniques, nor among labs using different wavelengths of IR laser. UWG-2 is available for interlaboratory comparison, and for assessing the performance of microanalytical techniques including laser probes and ion microprobes with a recommended value of δ 18O = 5.8‰ SMOW. Multiple, daily analyses of UWG-2 at the University of Wisconsin provide an accurate evaluation of all components in our laser-probe, mass-spectrometer system, and allow analytical problems to be rapidly identified. With this standardization, the accuracy of a single laser probe analysis is better than ±0.10‰. Over 1000 analyses of UWG-2 have been made. The average of all uncorrected δ 18O values is 5.74 ± 0.15‰ (1 sd). The precision on a single day averages ±0.07‰ and is frequently better than 0.05‰. The uncertainty in the mean for all analyses is ±0.005‰ (1σ). A small drift of the daily average over time results from inevitable changes in the vacuum line which require careful attention and maintenance.
AB - UWG-2 is a new garnet standard for oxygen isotope analysis prepared from a single large porphyroblast that was homogeneous (±0.21‰) at the millimeter-scale before grinding. The δ 18O value of UWG-2 has been determined in seven laboratories using either a laser probe system or externally heated Ni reaction vessels. The raw laser probe value is 5.74‰ at the University of Wisconsin. If all data are normalized to NBS-28 = 9.59‰, then the UW value (5.89‰) is in good agreement with the average of all labs (5.78‰). There is no significant difference between garnet analyses made with the two techniques, nor among labs using different wavelengths of IR laser. UWG-2 is available for interlaboratory comparison, and for assessing the performance of microanalytical techniques including laser probes and ion microprobes with a recommended value of δ 18O = 5.8‰ SMOW. Multiple, daily analyses of UWG-2 at the University of Wisconsin provide an accurate evaluation of all components in our laser-probe, mass-spectrometer system, and allow analytical problems to be rapidly identified. With this standardization, the accuracy of a single laser probe analysis is better than ±0.10‰. Over 1000 analyses of UWG-2 have been made. The average of all uncorrected δ 18O values is 5.74 ± 0.15‰ (1 sd). The precision on a single day averages ±0.07‰ and is frequently better than 0.05‰. The uncertainty in the mean for all analyses is ±0.005‰ (1σ). A small drift of the daily average over time results from inevitable changes in the vacuum line which require careful attention and maintenance.
UR - http://www.scopus.com/inward/record.url?scp=0029474366&partnerID=8YFLogxK
U2 - 10.1016/0016-7037(95)00386-X
DO - 10.1016/0016-7037(95)00386-X
M3 - Comment/debate
AN - SCOPUS:0029474366
SN - 0016-7037
VL - 59
SP - 5223
EP - 5231
JO - Geochimica et Cosmochimica Acta
JF - Geochimica et Cosmochimica Acta
IS - 24
ER -