WSU CAHNRS

Washington State University

School of the Environment

Watershed Lab

Steffen Center

Forestry

Earth Science/Geology

XRF Precision

LOD = limit of determination in this table. We determined these 2 sigma limits by analyzing about 250 repeat experiments over the course of 14 months. These therefore represent our working day-in, day-out precision. Clearly if your concentration is less than our LOD your result is highly uncertain. In contrast to many other labs, we report results down to zero because there is information at 1 and 2 sigma even though most limits of detection are defined at three sigma. You can be 95% confident in our result at say 2 +/- 2 ppm, but strict detection limit usage would preclude reporting the number at all because you don’t have 99% confidence you have “detected” something. We are satisfied with the lesser confidence interval but you can choose your own usage.

WSU XRF precision, limit of determination (2-sigma)

Mar-06 Replicate r2 Replicate LOD
Unnormalized Major Elements (Weight %):
SiO2 0.99929 0.58
TiO2 0.99992 0.017
Al2O3 0.99949 0.16
FeO* 0.99948 0.20
MnO 0.99983 0.002
MgO 0.99994 0.076
CaO 0.99976 0.064
Na2O 0.99981 0.045
K2O 0.99992 0.031
P2O5 0.99990 0.005
Estimated LOI 0.966 1.00
SO3 0.989 0.07
Cl 0.992 0.002
Normalized Major Elements (Weight %):
SiO2 0.99992 0.19
TiO2 0.99996 0.012
Al2O3 0.99987 0.082
FeO* 0.99956 0.18
MnO 0.99988 0.002
MgO 0.99994 0.073
CaO 0.99998 0.043
Na2O 0.99989 0.036
K2O 0.99998 0.015
P2O5 0.99996 0.003
Trace Elements (ppm):
Ni 0.9992 3.5
Cr 0.9998 3.0
Sc 0.997 1.6
V 0.9996 5.0
Ba 0.9997 11.7
Rb 0.9998 1.7
Sr 0.99992 4.6
Zr 0.99994 3.9
Y 0.9987 1.2
Nb 0.99987 1.2
Ga 0.955 2.7
Cu 0.994 7.4
Zn 0.9991 3.3
Pb 0.9966 2.6
La 0.9941 5.7
Ce 0.996 7.9
Th 0.997 1.6
Nd 0.992 4.3
U 0.983 2.7
Bi 0.758 2.0
Cs 0.365 5.1

 

You can download a PDF of the LOD Table here.

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Peter Hooper GeoAnalytical Lab
School of the Environment

Webster 1228
Washington State University
Pullman, WA 99164-2812

Phone:509-335-1626
Fax: 509-335-3700
E-mail: geolab@wsu.edu

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