4E Research - INAA, Total Digestion - ICP, Lithium Metaborate/Tetraborate Fusion - ICP

INAA Portion

A 1 g aliquot is encapsulated in a polyethylene vial and irradiated with flux wires and an internal standard (1 for 11 samples) at a thermal neutron flux of 7 x 10¹² n cm^-2 s^-1. After a 7-day decay to allow Na-24 to decay the samples are counted on a high purity Ge detector with resolution of better than 1.7 KeV for the 1332 KeV Co-60 photopeak. Using the flux wires, the decay-corrected activities are compared to a calibration developed from multiple certified international reference materials. The standard present is only a check on accuracy and is not used for calibration purposes. From 10-30% of the samples are rechecked by re-measurement. For values exceeding the upper limits, assays are recommended.

One standard is run for every 11 samples. One blank is analyzed per work order. Duplicates are analyzed when samples are provided.

The method is described by Hoffman, E.L., 1992. Instrumental Neutron Activation in Geoanalysis. Journal of Geochemical Exploration, volume 44, pp. 297-319.

Major Elements Portion

A 0.2 g sample is mixed with a mixture of lithium metaborate/lithium tetraborate and fused in a graphite crucible. The molten mixture is poured into a 5% nitric acid solution and shaken until dissolved (~ 30 minutes). The samples are run for major oxides and selected traces on a combination simultaneous/sequential Thermo Jarrell-Ash Enviro II ICP. Calibration is achieved using a variety of international reference materials. Independent control standards are also analyzed. Results on the international standards run with the samples are appended at the end of the report.

Base Metals and Selected Trace Elements

A 0.25 g sample is digested with four acids beginning with hydrofluoric, followed by a mixture of nitric and perchloric acids, heated using precise programmer controlled heating in several ramping and holding cycles which takes the samples to dryness. After dryness is attained, samples are brought back into solution using hydrochloric acid. With this digestion certain phases may be only partially solubilized. These phases include zircon, monazite, sphene, gahnite, chromite, cassiterite, rutile and barite. Ag greater than 100 ppm and Pb greater than 5,000 ppm should be assayed as high levels may not be solubilized. Only sulphide sulfur will be solubilized.

An in-lab standard (traceable to certified reference materials) or certified reference materials are used for quality control.

Samples are analyzed using a Perkin Elmer Optima 3000 ICP.

Code 4E-research Fusion ICP

Oxide	Detection Limit
SiO₂	0.01%
Al₂O₃	0.01%
Fe₂O₃	0.01%
MgO	0.01%
MnO	0.001%
CaO	0.01%
TiO₂	0.001%
Na₂O	0.01%
K₂O	0.01%
P₂O₅	0.01%
Loss on Ignition	0.01%

Code 4E-research Trace Elements and Detection Limits (ppm)

Element	Detection Limit	Upper Limit	Reported By	Element	Detection Limit	Upper Limit	Reported By
Ag	0.5	100,000		Nd	1	10,000	INAA
As	1	-	INAA	Ni	1	10,000
Au	1 ppb	30,000 ppb	INAA	Pb	5	5,000
Ba	1	-		Rb	10	-	INAA
Be	1	10,000		S	0.001%	20%
Bi	2	10,000		Sb	0.1	10,000	INAA
Br	0.5	-	INAA	Sc	0.01	-	INAA
Cd	0.5	5,000		Se	0.5	-	INAA
Ce	1	10,000	INAA	Sm	0.01	10,000	INAA
Co	0.1	10,000	INAA	Sr	2	-
Cr	0.5	100,000	INAA	Ta	0.3	10,000	INAA
Cs	0.2	-	INAA	Tb	0.1	-	INAA
Cu	1	10,000		Th	0.1	10,000	INAA
Eu	0.05	-	INAA	U	0.1	10,000	INAA
Hf	0.2	-	INAA	V	5	-
Hg	1	-	INAA	W	1	10,000	INAA
Ir	1 ppb	-	INAA	Y	1	10,000
La	0.05	10,000	INAA	Yb	0.05	-	INAA
Lu	0.01	-		Zn	1	100,000
Mo	2	10,000		Zr	2	-	INAA

Typical ICP Analysis of some USGS and Canmet Standards (%)

Std.	SiO₂	Al₂O₃	Fe₂O₃	MnO	MgO	CaO	Na₂O	K₂O	TiO₂	P₂O₅
SY3	59.51	11.62	6.47	0.32	2.54	8.25	4.17	4.23	0.14	0.52
MRG1	39.43	8.59	17.93	0.17	13.74	14.77	0.73	0.18	3.78	0.07
DNC1	46.91	18.46	9.76	0.15	10.05	11.27	1.99	0.24	0.47	0.07
BIR1	47.78	15.43	11.52	0.17	9.70	13.75	1.86	0.02	0.95	0.02
W2	52.58	15.35	10.72	0.16	6.37	10.98	2.31	0.64	1.05	0.12
G2	68.72	14.95	2.65	0.03	0.71	1.87	4.08	4.48	0.48	0.13
STM1	59.64	18.07	5.24	0.22	0.07	1.09	8.87	4.24	0.13	0.1

Code 4E-research Options

4E-XRF

The trace elements analyses are done on pressed powder pellets made from 6 g of sample. Spectral interferences are corrected from pre-calculated interfering factors. Because of the trace level (< 1000 ppm) of the analytes, only the mass absorptions are corrected for matrix effects. The mass absorption coefficients are derived from measuring the Compton scatter of the Rh-tube (e.g., Nisbet et al., (1979), Fortschr. Miner., v. 57, p. 264-279). The background and mass absorption corrected intensities are then calculated against the calibrations constructed from 24 international geological reference materials. In general, the limits of detection are between 1 to 5 ppm.

Option 4E-XRF Elements and Detection Limits (ppm)

Element	Detection Limit	Upper Limit
Ga	5	10,000
Pb	5	1,000
Sn	5	10,000
Nb	1	10,000
Rb	2	20,000

4E ICP/MS

Fused sample is diluted and analyzed by Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP/MS. Three blanks and five controls (three before sample group and two after) are analyzed per group of samples. Duplicates are fused and analyzed every 15 samples. Instrument is recalibrated every 40 samples.

Option 4E ICP/MS Elements and Detection Limits (ppm)

Element	Detection Limit	Upper Limit	Element	Detection Limit	Upper Limit	Element	Detection Limit	Upper Limit
Bi	0.01	10,000	Ho	0.01	-	Sn	1	1,000
Ce	0.05	3,000	In	0.1	200	Ta	0.01	500
Cs	0.1	1,000	La	0.05	10,000	Tb	0.01	-
Dy	0.01	1,000	Lu	0.002	-	Th	0.05	1,000
Er	0.01	-	Mo	2	100	Tl	0.05	1,000
Eu	0.005	-	Nb	0.2	10,000	Tm	0.005	-
Ga	1	10,000	Nd	0.05	-	U	0.01	1,000
Gd	0.01	1,000	Pr	0.01	1,000	Yb	0.01	-
Ge	0.5	10,000	Rb	1	10,000	Zr	1	10,000
Hf	0.1	100	Sm	0.01	-

Printed from: Actlabs
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