the determination of 30 elements in geological materials

The Determination of 30 Elements in Geological Materials by Energy-Dispersive X-ray Fluorescence Spectrometry

by David F. Siems1

Open-File Report 00-475

2000

This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Any use of trade names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

'U.S. Geological Survey, Box 25046, Mail Stop 973, DFC, Denver, CO 80225-0046

Table of Contents

List of Tables..............................................................................3

Introduction................................................................................4

Principle....................................................................................4

Interferences............................................................................... 4

Scope....................................................................................... 5

Apparatus..................................................................................5

Calibration Standards....................................................................5

Safety Precautions........................................................................6

Procedure..................................................................................6

Calculations...............................................................................6

Assignment of Uncertainty..............................................................7

References Cited.........................................................................13

List of Tables

Table 1. Elements analyzed and lower limits of determination (LLD) for elemental analysis ofGeochemical samples.................................................................................... 5

Table 2. Calibration standards used in EDXRF method......................................................... 5

Table 3. Operating conditions for Spectro X-lab 2000 X-ray Spectrometer..................................6

Table 4. Analytical performance summary for elements in geological materials by EDXRF..............7

Introduction

This report describes the rapid, nondestructive procedure and validation of an Energy Dispersive X-ray Fluorescence Spectrometry (EDXRF) technique for the determination of 30 elements in geological materials. The precision, expressed as percent relative standard deviation (%RSD), is shown to be an average of 2.4% for elements whose concentration is >50ppm, 7.5% for elements whose concentration is < 50ppm and >3x lower limit of determination (LLD), and 18% for those elements whose concentration is < 3x LLD. The format of this report is consistent with other published methods that have been approved by the quality assurance coordinator.

Principle

EDXRF spectrometry is a qualitative and quantitative technique for the rapid, non-destructive, elemental analysis of liquid and solid samples. Sample preparation is a simple matter of lightly pressing a powdered geologic sample into a Mylar cup fitted with a Prolene foil. Then the sample is bombarded by X-rays of a selected energy and the characteristic X-ray photons of the analytes are detected and measured. By using selected secondary and polarizing targets a greater peak to background ratio for the various peaks are obtained than when using direct tube excitation. With this method 30 trace elements: V, Cr, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr, Nb, Mo, Ag, Cd, Sn, Sb, Cs, Ba, La, Ce, Nd, W, Pb, Bi, Th and U are determined routinely. The readers are referred to the literature (E. Bertin, 1975; Johnson and King, 1987; and King, 1987) for more details on the use of EDXRF for geologic and geochemical applications.

Interferences

Interferences in X-ray fluorescence consist of spectral-line overlaps, matrix effects, spectral artifacts, and particle size or mineralogical effects.

Peak overlaps occur when a peak of a different element is not able to be resolved from the element of interest. The most significant peak overlaps that occur in this procedure are as follows: Ti Kp and Ba Lp overlap the V Ka, V Kp on Cr Ka, Co Kp on Ni Ka, Ni Kp and W La on Cu Ka, W La on Zn Ka, W Lp on Ge Ka, Pb La on As Kp, Au Lp and Pb La on As Ka, As Kp on Br Ka, Th La and U La on Rb Ka, Rb Kp on Y Ka, Sr Kp on Zr Ka, Y Kp on Nb Ka, ZrKp,ULp on Mo Ka, Ag Kp on Sn Ka, Cd Kp on Sb Ka, Cu Ka and Zn Ka on W La , As Ka, Pb La and Se Ka on Bi La, Rb Ka and Bi Lp on Th La and RbKa and Sr Ka on ULa. These interferences are accounted for using linear and nonlinear fits of Gausian peaks and are removed using the computer algorithms provided with the software. Often an analyte whose concentration is >1000ppm cannot be deconvoluted from an adjacent element whose concentration is 1-5 ppm. These results are denoted by "inf' or interference.

Matrix effects occur when radiation from the characteristic elements are absorbed or enhanced by other elements in the sample before it reaches the detector. The effects are corrected by a scattered radiation method ( Anderman and Kemp, 1958) which has been used for routine trace analyses of geologic materials ( R.G. Johnson, 1984 and B.W. King, 1987). The method is based on the principle that the line intensities from the analyte line and the incoherent scatter peak (Compton peak) are effected in the same proportion due to the overall mass absorption coefficient of the sample. The ratio of the analyte line intensity to the Compton peak intensity is constant over a wide range of geologic matrices. This Compton peak method also helps to minimize the effects of particle size, packing density and short term minor drifts in tube current.

Spectral artifacts such as escape peaks, sum peaks, low energy line tailing, pulse pile up lines, and Bremsstralung correction are accounted for with the provided software.

Scope

Analysis by EDXRF for the above mentioned trace elements is applicable to a wide variety of geochemical samples including rocks, stream sediments, and soils presented as a powder (-120 mesh) packed to 10 foot pounds on a 1 inch diameter dye. The elements analyzed for and their reporting limits are shown in Table 1.

Table 1. Elements analyzed and the lower limits of determination (LLD) for elemental analysis of geological samples

ElementVanadium, VChromium, CrNickel, NiCopper, CuZinc, ZnGallium, GaGermanium, GeArsenic, AsSelenium, SeBromine, Br

LLD5 ppm3 ppm2 ppm2 ppm2 ppm2 ppm2 ppm2 ppm1 ppm1 ppm

ElementRubidium, RbStrontium, SrYttrium, YZirconium, ZrNiobium, NbMolybdenum, MoSilver, AgCadmium, CdTin,SnAntimony, Sb

LLD2 ppm2 ppm2 ppm2 ppm2 ppm1 ppm1 ppm1 ppm2 ppm

.iPPm.....

ElementCesium, CsBarium, BaLanthanum, LaCerium, CeNeodymium, NdTungsten, WLead. PbBismuth, BiThorium, ThUranium, U

LLD3 ppm3 ppm3 ppm3 ppm7 ppm5 ppm3 ppm5 ppm2 ppm

..!EEm.......

Apparatus

Spectro X-lab 2000 Energy Dispersive X-ray Spectrometer.Gresham high purity silicon (HP Sirius) liquid nitrogen cooled detector. Resolution at Mn Ka at 10000counts is 150eV.X-ray source 400 W - Paladium end - window tubePana-vise with torque wrench set to 10 foot poundsChemplex cups, 32mmProlene Firm support thickness 4(j. (0.16 mil)

Calibration Standards

Table 2. lists the 58 reference standards used for the calibration of this technique. Values are obtained from Govindaraju, 1989 and 1994, National Institute of Standards & Technology (NIST) Certificates of Analysis, U.S. Geological Survey Certificate of Analysis and recommended values obtained on USGS internal laboratory standards.

Table 2. Calibration standards used in the EDXRF method

AGV-1GH-NMA-N

PACS-1KRS1-5

BCS-375GS-NMAG-1

PCC-1KRS-12

BHVO-1GSD-1 thru GSD-12MICA-FE

RGM-1KRS3-5

BIR-1GSP-1MRG-1

SDO-1KRS6-5

BR-NGSR-1NIM-L

STM-1

JS2L,

DR-NGSR-4NOD-P-1

SY-3DGPM-2

DTS-1GSS-1 thru GSS-7NBS-88b,278,1646and 1633aUB-N

G-2JP-1SY-2

W-2

Safety Precautions

The Spectro X-lab 2000 is adequately shielded to prevent X-rays from escaping into the lab area. The system is monitored routinely with a radiation-survey meter at intervals of 6 months. In addition, all laboratory personnel are required to wear a radiation safety badge when operating the X-ray system.

Procedure

A 2- to 3-g portion of the powdered sample or reference material is poured into a spectro cup fitted with a bottom of stretched 4fi Prolene film held with a concentric ring. This requires no weighing. The powder is then packed into the cup at approximately 10 lbs/in2 using the Panavise with torque wrench.

Table 3. Operating conditions for Spectro X-lab 2000 X-ray Spectrometer

Mo secondary target Determination of Compton and Raleigh Mo Ka peak intensities A12O3 polarizing target Mo, Ag, Cd, Sn, Sb. Cs, Ba, La, Ce, and Nd determinations - Ka line Boron Carbide B4C Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr and Nb determinations Ka Polarizing target line

W, Bi,Th, and U determinations - La linePb determination - L(3 line

Cobalt secondary target V and Cr determinations - Ka lineExcitation target voltages 40 kV for Mo, 53kV for A12O3, 44kV for B4C and 35kV for Co targets Excitation target current Current is optimized to reach a dead time of 50% Acquisition tinie( live ^i^

Up to 20 sample positions can be used in the sample holder. 18 are job samples and 2 are selected reference materials for the quality control of the instrument. The sample ID numbers, job numbers and analytical programs are entered into the computer that operates the instrument. A total of 36 samples can be analyzed in a 24-hour period allowing for automatic operation of the instrument overnight. Spectrum deconvolution:

Subtraction of escape lines Correction of the detector shelf channel per channel Subtraction of the pile up lines Correction of the Bremsstralung created in the sample Subtraction of incomplete polarized scattering radiation or of the

scattered radiation of secondary targets Correction of the low energy line tailing Determination of matrix dependent element specific line ratios Recalibration of the channel-energy-calibration and the width-energy-

calibration using the zero-peak Linear and nonlinear fit of the Gaussian peaks Calculation of net peak intensities

The ratios of peak intensity to the Mo Compton scatter intensity are used in a linear least-squares fit of the concentration data for each element.

Calculations

The concentration Q of element I, in the unknown sample is calculated from the intercept B0 and slope B! of the best fit line of calibration and the ratio of intensity I; to Compton scatter radiation C as follows:

Assignment of Uncertainty

The counting error aN , where aN is the standard deviation in terms of the accumulated count R in X-ray spectroscopy is that error arising only from the random arrival of x-ray photons to the detector. This error is represented by the following equation:

aN represents the best precision that can be obtained on a particular sample and can be used as a standardagainst which the actual measured precision can be judged.The total sources of error are the counting error, the instrument stability error, the specimen preparationerror, operational error, and miscellaneous errors.Table 4. represents the statistical summary for the analysis of 7 geological standard reference materials.

Table 4. Analytical performance summary for elements in geological materials by EDXRF

Reference Description n Mean aN pv %RSD %R

AgppmBHVO-2AGV-2BCR-2GSP-2TILL-4STSD-2

NBS-2711

BasaltAndesite

BasaltGranodiorite

TillStream sed

Soil

10 <110 <110 <110 <110 <110 0.510 4.6

NANANANANANA0.3

NANANANANANA0.3

NRNRNRNRNR<15.9

NANANANANANA5.2

NANANANANANA-22

AsppmBHVO-2AGV-2BCR-2GSP-2

STSD-2NBS-2711

TILL-4

BasaltAndesite

BasaltGranodioriteStream sed

SoilTill

10101010101010

<2<2<2<242111117

NANANANA1.64.81.7

NANANANA0.71.90.9

NRNRNRNR42105111

NANANANA1.71.70.8

NANANANA

0+6+5

BappmBHVO-2TILL-4STSD-2BCR-2

NBS-2711AGV-2

BasaltTill

Stream sedBasalt

SoilAndesite

101010101010

1283915236467101127

1.72.32.72.82.93.9

2.74.65.36.61015

1303955406837261140

2.11.21.01.01.41.3

-2-1-3-5-2-1


BippmBHVO-2AGV-2BCR-2GSP-2

STSD-2NBS-2711

TILL-4

BrppmBHVO-2AGV-2BCR-2GSP-2

STSD-2NBS-2711

TILL-4

CdppmBHVO-2AGV-2BCR-2GSP-2TILL-4STSD-2

NBS-2711

CeppmBHVO-2BCR-2AGV-2

NBS-2711TILL-4STSD-2GSP-2

CrppmBCR-2GSP-2AGV-2

NBS-2711TILL-4STSD-2

BHVO-2

CsppmBHVO-2AGV-2BCR-2GSP-2

STSD-2TILL-4

NBS-2711

BasaltAndesiteBasalt

GranodioriteStream sed

SoilTill

BasaltAndesite


SoilTill

BasaltAndesite

BasaltGranodiorite

TillStream sed

Soil

BasaltBasalt

AndesiteSoilTill

Stream sedGranodiorite

BasaltGranodiorite

AndesiteSoilTill

Stream sedBasalt


GranodioriteStream sed

TillSoil

10101010101010

10101010101010

10101010101010

10101010101010

10101010101010

10101010101010

<5<5<5<5<5<539

<1<1<1<13.85.68.0

<1<1<1<1<1<148

344865668087

468

1417214851121314

<3<3<3<31113

7.0

NANANANANANA1.4

NANANANA0.40.50.5

NANANANANANA0.7

2.42.52.72.62.62.73.65

2.11.41.21.11.11.63.4

NANANANA0.90.90.6

NANANANANANA1.0

NANANANA0.40.51.0

NANANANANANA2.9

3.22.22.82.62.53.74.5

2.01.21.11.21.95.13.2

NANANANA0.80.61.1

NRNRNRNRNRNR40

NRNRNRNR4.05.08.6

NRNRNRNRNR0.841

385368697893

410

1820174753116280

NR1.21.11.212126.1

NANANANANANA2.5

NANANANA9.39.82.5

NANANANANANA6.0

9.44.64.33.93.24.21.0

117.15.42.63.74.21.1

NANANANA7.44.915

NANANANANANA-3

NANANANA-5

+12-7

NANANANANANA+17

-11-9-4-4+3-6

+14

-22-15+23+2-4+4+12

NANANANA-8+8+15

Reference

Cu ppmBCR-2GSP-2

STSD-2AGV-2

NBS-2711BHVO-2TILL-4

GappmNBS-2711

TILL-4STSD-2

BHVO-2AGV-2GSP-2BCR-2

GeppmBHVO-2AGV-2BCR-2GSP-2TILL-4STSD-2

NBS-2711NBS-1633a

La ppmBHVO-2BCR-2

NBS-2711AGV-2TILL-4STSD-2GSP-2

Mo ppmNBS-2711

AGV-2GSP-2

BHVO-2STSD-2TILL-4BCR-2

Nb ppmBCR-2AGV-2

NBS-2711TILL-4

BHVO-2

Description

BasaltGranodioriteStream sedAndesite

SoilBasalt

Till

SoilTill

Stream sedBasalt

AndesiteGranodiorite

Basalt

BasaltAndesite

BasaltGranodiorite

TillStream sed

SoilFly Ash

BasaltBasalt

SoilAndesite

TillStream sed

Granodiorite

SoilAndesite

GranodioriteBasalt

Stream sedTill

Basalt

BasaltAndesite

SoilTill

Basalt

n

10101010101010

10101010101010

1010101010101010

10101010101010

10101010101010

1010101010

Mean

17404551108135248

13172121212223

<2<2<2<2<2<2<239

132236384151

204

2.42.64.05.31316

239

1214141519

aN

1.91.92.02.12.73.63.8

2.01.0l.l1.31.11.11.3

NANANANANANANA1.2

1.71.81.92.01.92.02.6

0.70.81.00.90.91.02.9

0.50.40.40.40.5

s

2.02.03.22.04.33.55.6

1.91.51.52.01.20.81.0

NANANANANANANA1.6

1.92.21.31.82.12.43.1

0.60.61.30.70.90.94.8

0.70.40.40.30.7

Pv

19434753114127237

15NRNR22202223

NRNRNRNRNRNRNR34

152540384159180

1.6NR2.1NR1316

248

NR15

NR1518

%RSD

115.17.03.84.02.62.3

148.57.09.55.63.64.3

NANANANANANANA4.1

149.83.74.85.24.71.5

242232136.85.92.0

6.02.6

2.8%1.93.5

%R

-11-7-4-4-5+6+5

-13NANA-5+500

NANANANANANANA+12

-15-13-1000

-14+13

+50NA+90NA

00-4

NA-7

NA0

+6

Reference

Nb ppmSTSD-2GSP-2

NdppmBHVO-2BCR-2

NBS-2711AGV-2TILL-4STSD-2GSP-2

Ni ppm BCR-2GSP-2TILL-4AGV-2

NBS-2711STSD-2

BHVO-2

Pb ppmBHVO-2BCR-2AGV-2GSP-2TILL-4STSD-2

NBS-2711

Rb ppmBHVO-2BCR-2AGV-2STSD-2

NBS-2711TILL-4GSP-2

Sb ppmBHVO-2AGV-2BCR-2GSP-2TILL-4STSD-2

NBS-2711

SeppmBHVO-2AGV-2

Description

Stream sedGranodiorite

BasaltBasalt

SoilAndesite

TillStream sed

Granodiorite

BasaltGranodiorite

TillAndesite

SoilStream sed

Basalt

BasaltBasalt

AndesiteGranodiorite

TillStream sed

Soil

BasaltBasalt

AndesiteStream sed

SoilTill

Granodiorite


GranodioriteTill

Stream sedSoil

BasaltAndesite

n

1010

10101010101010

10101010101010

10101010101010

10101010101010

10101010101010

1010

Mean

2026

232831313444

214

111516182159122

3.91214435275

1147

9.94969100114166245

<2<2<2<2<23.718

<1<1

CTN

0.40.4

5.25.85.76.05.55.76.0

1.61.71.61.81.72.54.1

0.91.11.01.31.41.65

0.40.70.70.80.81.01.2

NANANANANA0.20.4

NANA

s

0.70.7

1.84.15.26.24.38.55.6

2.01.71.01.21.11.84.9

0.51.10.81.01.21.74.3

0.51.40.90.91.01.21.4

NANANANANA0.32.0

NANA

pv

2027

252831303043

200

101717192153119

NR1113425066

1162

9.84869104110161245

NRNRNRNR1.04.819

NRNR

%RSD

3.72.7

7.21417201319

2.6

1811

6.46.65.43.14.0

129.55.32.32.32.20.4

5.42.91.30.90.90.70.6

NANANANANA9.211

NANA

%R

0-4

-800

+3+ 13+2+7

+ 10-12-6-50

+ 11+3

NA+9+8+2+4

+ 14-1

+1+20-4+4+30

NANANANANA-23-5

NANA

10

Reference

SeppmBCR-2GSP-2

STSD-2TILL-4

NBS-2711

Sn ppmAGV-2

BHVO-2BCR-2STSD-2

NBS-2711GSP-2TILL-4

Sr ppmTILL-4

NBS-2711GSP-2BCR-2

BHVO-2STSD-2AGV-2

ThppmBHVO-2AGV-2BCR-2

NBS-2711STSD-2TILL-4GSP-2

UppmBHVO-2AGV-2BCR-2

NBS-2711GSP-2TILL-4STSD-2

VppmGSP-2TILL-4

NBS-2711STSD-2AGV-2

BHVO-2BCR-2

tnjVWUVUWW^AVnVUVVVAMV^.V.%V

Description


TillSoil

AndesiteBasaltBasalt

Stream sed. Soil

GranodioriteTill

TillSoil

GranodioriteBasaltBasalt

Stream sedAndesite


SoilStream sed

TillGranodiorite


SoilGranodiorite

TillStream sed

GranodioriteTillSoil

Stream sedAndesiteBasaltBasalt

n

1010101010

10101010101010

10101010101010

10101010101010

10101010101010

10101010101010

Mean

<1<1<11.21.4

2.32.42.63.44.66.812

115222238343394417654

<24.24.68.81723111

3.23.43.44.65.26.018

516772100109308429

ON

NANANA.5

0.7

0.10.20.20.20.20.20.3

0.71.01.11.51.71.41.9

NA0.30.30.50.50.81.0

0.70.91.31.41.61.61.4

3.02.72.73.43.97.88.2

s

NANANA0.20.3

0.40.20.40.20.60.70.9

1.20.8102.33.24.25.7

NA0.60.70.80.80.70.9

0.40.90.70.61.00.71.1

2.53.32.94.8125.712

pv

NRNRNRNR1.5

2.31.9NR5.0NRNRNR

109245240346389400658

1.26.16.2141717

105

NR1.91.72.62.45.019

526782101120317416

%RSD

NANANA1424

178.1156.61410

7.1

1.00.44.20.70.81.00.9

NA9.8118.84.93.30.8

1328211420126.4

4.94.94.14.6111.52.9

%R

NANANANA-7

0+26NA-32NANANA

+6-9-1-1+1+4-1

NA+31-26-370

+35+6

NA+79+100+77+116+20-5

-20

-12-1-9-3+3

11


WppmBHVO-2AGV-2BCR-2GSP-2

NBS-2711STSD-2TILL-4

Y ppmAGV-2

NBS-2711BHVO-2

GSP-2TILL-4BCR-2STSD-2

Zn ppmTILL-4AGV-2

BHVO-2GSP-2BCR-2STSD-2

NBS-2711

Zr ppmBHVO-2STSD-2BCR-2AGV-2

NBS-271 1TILL-4GSP-2


GranodioriteSoil

Stream sedTill

AndesiteSoil

BasaltGranodiorite

TillBasalt

Stream sed

TillAndesiteBasalt

GranodioriteBasalt

Stream sedSoil

BasaltStream sed

BasaltAndesite

SoilTill

Granodiorite

10101010101010

10101010101010

10101010101010

10101010101010

<5<5<5<5<55.1190

20NR*2727304137

7191106124129260360

172174187229267350541

NANANANANA2.74.6

0.5NA0.50.70.60.60.6

1.92.12.62.32.83.33.7

1.21.01.21.21.01.11.5

NANANANANA2.05.9

0.6NA1.20.70.83.60.6

2.32.16.02.82.64.04.2

113.41.21.41.96.67.6

NRNRNRNR3.07.0204

20252628333737

7086103120127246350

172185188230230385550

NANANANANA393.1

3.2NA4.32.72.68.91.5

3.32.45.82.32.01.51.2

6.42.00.60.60.71.91.4

NANANANANA-27-7

0NA+4-4-9

+110

+1+6+3+3+2+6+3

0-6-1-1

+16-9-2

* When Pb is greater than 500 ppm, Y is reported as "inf' or interference.

n = number of samplespv = proposed value taken from published reference material compilation

BHVO-2, AGV-2, BCR-2, and GSP-2 (U. S. Geological SurveyCertificates of Analysis)TILL-4 (CCRMP, 1995)STSD-2 (Lynch, 1990) and (Govindaraju, 1994)NBS-1633a (Govindaraju, 1989)

aN = 1-sigma standard deviation in terms of accumulated count or the best standard deviation to beexpected

s = 1-sigma standard deviation %RSD = 1-sigma percent relative standard deviation%R = percent difference between the recommended value and the mean of the EDXRF technique NR = not reported NA = not applicable

12

References Cited

Anderman, G., and Kemp, J.W., 1958, Scattered X-rays as internal standards in X-ray emission Spectroscopy: Analytical Chemistry, 30, 8, p. 1306-1309.

Arbogast, Belinda, F. editor, 1996, Analytical methods manual for the Mineral Resource Surveys Program, U.S. Geological Survey: U.S. Geological Survey Open File Report 96-525 248p.

Bertin, Eugene P., 1975, Principals and practice of X-ray spectrometric analysis: Plenum Press.

Canadian Certified Reference Materials Project, 1995, Certificate of Analysis, Till-1, Till-2 Till-3, and Till-4.

Govindaraju, K., 1989, 1989 Compilation of working values and sample description for 272 geostandards: Geostandards Newsletter, v. 8, Special Issue, 113p.

Govindaraju, K., 1994, 1994 Compilation of working values and sample description for 383 geostandards: Geostandards Newsletter, v. 18, Special Issue, 158p.

Johnson, R.G., 1984, Trace element analysis of silicates by means of energy-dispersive X-ray Spectrometry: X-ray Spectrometry, 13, p. 64-68.

Johnson, R.G. and B.-S.L. King, 1987, Energy-dispersive X-ray fluorescence Spectrometry, in Baedecker, P.A., Methods for geochemical analyses: U.S. Geological Survey Professional Paper 1770, P. F1-F5.

King, B.W., 1987, Determination of trace elements in eight Chinese stream sediment reference samples by Energy-dispersive X-ray Spectrometry: Geostandards Newsletter, 11, p. 193-195.

National Institute of Standards & Technology, 1993, Montana Soil, 2711: Certificate of Analysis.

Taggart, Joseph E., Jr., Lindsey, J.R., Scott, B.A., Vivit, D.V., Bartel, A.J., and Stewart, K.C., 1987, Analysis of geologic materials by wavelength-dispersive X-ray fluorescence Spectrometry, in Baedecker, P.A., Methods for geochemical analyses: U.S. Geological Survey Professional Paper 1770, P. E1-E19.

U.S. Geological Survey, 1998, Andesite, AGV-2: Certificate of Analysis (Preliminary).

U.S. Geological Survey, 1998, Basalt, Columbia River, BCR-2: Certificate of Analysis.

U.S. Geological Survey, 1998, Basalt, Hawaiian Volcanic Observatory, BHVO-2: Certificate of Analysis.

U.S. Geological Survey, 1998, Granodiorite, Silver Plume, Colorado, GSP-2: Certificate of Analysis.

Wilson, S., 2000, U.S. Geological Survey analysis of DGPM-2, KRS1-5, KRS-12, KRS3-5, KRS6-5.

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the determination of 30 elements in geological materials

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