Southern Connecticut State University

                                Earth Science X-ray Analysis Laboratory

XRF Lab Procedures

The Earth Science X-ray Laboratory at Southern Connecticut State University produces chemical analyses of geological materials using Energy-Dispersive Polarization X-ray Fluorescence (EDPXRF) spectrometry.  The EDPXRF technique is a variation of secondary target, energy dispersive XRF.  The Spectro Analytical X-Lab 2000 XRF spectrometer used for the analyses incorporates a 400 watt Pd end-window x-ray tube that can be focused on various secondary targets to produce polarized or near monochromatic x-rays for optimal sample excitation.  The polarized x-ray beam produced by the instruments unique Cartesian geometry and Bragg crystal and Barkla scattering targets yields enhanced peak to background ratios compared to direct excitation or conventional secondary excitation EDXRF instruments.

Fused glass disks:

Fused glass disks are produced using  0.3000 grams of pre-ignited sample powder mixed with 2.4000 grams of a premixed anhydrous flux consisting of 35.3% lithium tetraborate and 64.7% lithium metaborate (eutectic composition).  The flux-sample mixture is fused in Pt- 5%Au crucibles using a muffle furnace set at 1030-1060°C.  Glass disks are hand cast with an aluminum plunger on a graphite platen.  Calibration parameters have been determined by the Alpha normalization method of deJongh.  Because of the large dilution of the original sample that occurs during production of the glass disks, trace element concentrations are better determined by the pressed powder pellet technique described below.

Pressed powder pellets:

Pressed powder pellets are produced using 0.900 grams of a  binder material (N, N –Ethylenebisstearamide, Primier Lab Supply Pelletblend powder) and 4.000 grams of very finely ground sample powder. The mixture is blended in a glass vial and pressed at 15 tons in a 32mm stainless steel pellet-die.  The pellet-die surface is covered with a 6 mm mylar film to avoid metal contamination (Fe, Cr, Ni) from the die surface.   Elements heavier than Cr are calibrated using an extended Compton model based on the intensity of the Compton radiation scattered from the sample by the Mo secondary target.  Elements lighter than Cr are calibrated using a model based on a combination of fundamental parameter and extended Compton methods that has been developed by the instrument manufacturer (Turboquant).  Pressed powder pellet results for the lighter elements, in particular those < Si, are only considered qualitative because their accuracy suffers significantly from particle size and mineralogical affects associated with the pelletized powders.  The lighter elements (most major elements) are better analyzed quantitatively by fusion techniques described above.

Calibration Standards:

            Bureau of Analyzed Samples Ltd (BAS), United Kingdom  BCS-353, BCS-354, BCS-877-1

            Canadian Certified Reference Materials Project (CCRMP), Canada  MRG-1, SY-3

            Centre de Recherches Pétrographiques et Géochimiques (CRPG), France AC-E, Al-I, AN-G, BE-N, BX-N, DR-N, DT-N,

                                                          FK-N, GA, GH, GS-N, IF-G, MA-N, MDO-G, MICA-FE, MICA-MG, PM-S, UB-N, WS-E

            Czechoslovak Metrology Institute, Czechoslovakia ECO-12-1-04

            Institute of Geophysical and Geochemical Exploration (IGGE), China GSD-11, GSR-02, GSR-08

            Institute of Mineral Raw Materials, Czechoslovakia SPS, MK

            Geological Survey of Japan (GSJ), Japan  JA-2, JA-3, JB-1b, JB-2, JB-3, JCFA-1, JF-1, JF-2, JG-1a, JG-2, JG-3, JGb-1,

                                                                          JGb-2, JH-1, JLk-1, JMn-1, JP-1, JR-1, JR-2, JR-3, JSl-1, JSO-1, JSO-2, JSy-1

            National Institute of Standards and Technology (NIST), USA NBS-120c, NIST-696

            South Africa Bureau of Standards (SABS), South Africa SARM-05, SARM-08, SARM-13, SARM-16, SARM-19, SARM-20

            United States Geological Survey (USGS), USA  AGV-2, BCR-2, BHVO-2, BIR-1, DNC-1, DTS-2, G-2, GSP-2, MAG-1

                                                                                 QLO-1, RGM-1, SCO-1, SDC-1, STM-1, W-2

            Zentrales Geologisches Institut (ZGI), Germany  AN, GM, GnA

Jb-1b

1σ

n=10 §

%1σ

Rec. Value

GSJ

1σ

n=10

†

Rec. Value

GSJ

97-51-53

1σ

n=3

 §

%1σ

SiO₂

0.21

TiO₂

0.02

Al₂O₃

0.07

Fe₂O₃

0.12

MnO

0.002

MgO

0.09

CaO

0.04

Na₂O

0.13

K₂O

0.03

P₂O₅

0.01

V

19

Cr

Ni

1.3

Cu

5.8

Zn

2.9

Rb

2.9

Sr

4.1

Y

3.5

Zr

1.9

Ba

11.6

Pb

1.1