4 ACID “NEAR TOTAL” DIGESTION

This acid attack is the most vigorous digestion used in geochemistry analysis and uses hydrochloric, nitric, perchloric and hydrofluoric acids.

Even with this 4 Acid “near total” digestion, certain minerals (barite, gahnite, chromite, cassiterite, etc.) may only be partially dissolved or stable in solution. Other minerals including zircon, sphene and magnetite may not be totally dissolved. Most other silicates will be dissolved, however some elements will be erratically volatilized, including As, Sb, Cr, U and Au.

Near-Total digestion cannot be used to obtain accurate determinations of REE, Ta, Nb, As, Sb, Sn, Hg, Cr, Au and U.

A 0.25g sample is digested with four acids beginning with hydrofluoric, followed by a mixture of nitric and perchloric acids. This is then heated using precise programmer controlled heating in several ramping and holding cycles which takes the samples to incipient dryness. After incipient dryness is attained, samples are brought back into solution using aqua regia.

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 5000 ppm should be assayed as high levels may not be solubilized. Only sulphide sulfur will be solubilized.

The samples are then analyzed using an Agilent 735 ICP. QC for the digestion is 14% for each batch, 5 method reagent blanks, 10 in-house controls, 10 samples duplicates, and 8 certified reference materials. An additional 13% QC is performed as part of the instrumental analysis to ensure quality in the areas of instrumental drift.

Elements and Detection Limits (ppm except where noted)

Element Detection LimitUpper Limit
Ag0.3100
Al0.01%50%
As 35,000
Ba 71,000
Be110,000
Bi210,000
Ca0.01%70%
Cd0.32,000
Co110,000
Cr 110,000
Cu110,000
Fe0.01%50%
Element Detection LimitUpper Limit
Ga110,000
Hg1-
K0.01%10%
Li110,000
Mg0.01%50%
Mn1100,000
Mo110,000
Na0.01%10%
Ni110,000
P0.001%10%
Pb35,000
S+0.01%20%
Element Detection LimitUpper Limit
Sb510,000
Sc410,000
Sr110,000
Te210,000
Ti0.01%10%
Tl510,000
U1010,000
V210,000
W510,000
Y11000
Zn110,000
Zr510,000

Notes: Extraction of each element by Total Digestion is dependent on mineralogy.

+ Sulphide sulphur and soluble sulphates are extracted

Assays are recommended for values which exceed the upper limits.

A 0.25g sample is digested with four acids beginning with hydrofluoric, followed by a mixture of nitric and perchloric acids. This is then 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 and nitric acids. This digestion may not be completely total if resistate minerals are present. As, Sb and Cr may be partially volatilized.

Digested samples are diluted and analyzed by Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP/MS. One blank is run for every 40 samples. In-house control is run every 20 samples. Digested standards are run every 80 samples. After every 15 samples, a digestion duplicate is analyzed. Instrument is recalibrated every 80 samples. An in-lab standard (traceable to certified reference materials) or certified reference materials are used for quality control.

Elements and Detection Limits (ppm)

Element Detection LimitUpper Limit
Ag0.1100
Al 0.01 %20 %
As 110,000
Ba 110,000
Be11,000
Bi0.14,000
Ca0.01 %40 %
Cd0.14,000
Ce12,000
Co0.24,000
Cr 110,000
Cs0.110,000
Cu0.110,000
Fe 0.01 %60 %
Element Detection LimitUpper Limit
Hf0.11,000
K0.01 %10 %
La 0.12,000
Li0.12,000
Mg0.01 %30 %
Mn110,000
Mo0.14,000
Na0.001 %10 %
Nb0.12,000
Ni0.110,000
P0.001 %5 %
Pb0.15,000
Rb0.12,000
S +1 %10 %
Element Detection LimitUpper Limit
Sb 0.14,000
Sc
1200
Sn0.12,000
Sr110,000
Ta 0.12,000
Th 0.14,000
Ti0.001 %10 %
Tl0.0510,000
U0.14,000
V410,000
W0.1200
Y 0.12,000
Zn110,000
Zr0.12,000

Notes: Extraction of each element by Total Digestion is dependent on mineralogy.

+ Sulphide sulphur and soluble sulphates are extracted

A 0.25g 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 and nitric acids. This digestion may not be completely total if resistate minerals are present. As, Sb and Cr may be partially volatilized.

Digested samples are diluted and analyzed by Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP-MS. One blank is run for every 40 samples. In-house control is run every 20 samples. Digested standards are run every 80 samples. After every 15 samples, a digestion duplicate is analyzed. Instrument is recalibrated every 80 samples. An in-lab standard (traceable to certified reference materials) or certified reference materials are used for quality control.

Elements and Detection Limits (ppm except where noted)

Element Detection LimitUpper Limit
Ag0.05100
Al0.01%10%
As0.110,000
B206000
Ba15,000
Be0.11,000
Bi0.022,000
Ca0.01%50%
Cd0.11,000
Ce0.110,000
Co0.1500
Cr15,000
Cs0.05100
Cu0.210,000
Dy0.15,000
Er0.11,000
Eu0.05100
Fe0.01%50%
Ga0.1500
Gd0.15,000
Element Detection LimitUpper Limit
Ge0.1500
Hf0.1500
Hg10 ppb10,000 ppb
Ho0.11,000
In0.1100
K0.01%5%
La0.110,000
Li0.5400
Lu0.1100
Mg0.01%50%
Mn110,000
Mo0.0510,000
Na0.01%3%
Nb0.1500
Nd0.110,000
Ni0.55,000
Pb0.55,000
Pr0.11,000
Rb0.25000
Re0.001100
Element Detection LimitUpper Limit
Sb0.1500
Se0.11,000
Sm0.1100
Sn1200
Sr0.21,000
Ta0.11000
Tb0.1100
Te0.1500
Th0.1500
Tl0.05500
Tm0.11000
U0.110,000
V11,000
W0.1200
Y0.110,000
Yb0.15,000
Zn0.210,000
Zr15,000

Notes: Extraction of each element by Total Digestion is dependent on mineralogy.

Unaltered silicates and resistate minerals may not be dissolved.

Ultratrace 6 combines the Total Digestion (HF, HClO4, HNO3 and HCl) with analysis by ICP and ICP-MS. Resistate minerals are not digested.

“Near Total” Digestion – ICP

A 0.25g 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 incipient dryness. After incipient dryness is attained, samples are brought back into solution using aqua regia.

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 5000 ppm should be assayed as high levels may not be solubilized. Only sulphide sulfur will be solubilized.

The samples are then analyzed using a Varian ICP. QC for the digestion is 14% for each batch, 5 method reagent blanks, 10 in-house controls, 10 samples duplicates, and 8 certified reference materials. An additional 13% QC is performed as part of the instrumental analysis to ensure quality in the areas of instrumental drift.

“Near Total” Digestion – ICP-MS

Additional elements are determined by ICP/MS on the multi-acid digest solution above. The samples are diluted and analyzed on a Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP/MS. One blank is run for every 40 samples. In-house control is run every 20 samples. Digested standards are run every 80 samples. After every 15 samples, a digestion duplicate is analyzed. Instrument is recalibrated every 80 samples.

Elements and Detection Limits (ppm)

Element Detection LimitUpper LimitReported By
Ag0.05100ICP&ICP/MS
Al0.01%10%ICP
As0.110,000ICP/MS
Ba15,000ICP/MS
Be0.11,000ICP/MS
Bi0.022,000ICP/MS
Ca0.01%50%ICP
Cd0.11,000ICP/MS
Ce0.110,000ICP/MS
Co0.1500ICP/MS
Cr 15,000ICP/MS
Cs0.05100ICP/MS
Cu0.210,000ICP/MS
Dy0.15,000ICP/MS
Er0.11,000ICP/MS
Eu0.05100ICP/MS
Fe0.01%50%ICP
Ga0.1500ICP/MS
Ge0.1500ICP/MS
Ge0.1500ICP/MS
Gd 0.15,000ICP/MS
Hf0.1500ICP/MS
Hg 10 ppb10,000 ppbICP/MS
Ho 0.11,000ICP/MS
In0.1100ICP/MS
K0.01%5%ICP
La 0.110,000ICP/MS
Li0.5400ICP/MS
Lu 0.1100ICP/MS
Mg0.01%50%ICP
Mn110,000ICP
Mo0.110,000ICP/MS
Element Detection LimitUpper LimitReported By
Na0.01%3%ICP
Nb0.1500ICP/MS
Nd0.110,000ICP/MS
Ni0.55,000ICP/MS
P0.001%10%ICP
Pb0.55,000ICP/MS
Pr 0.11,000ICP/MS
Rb0.25,000ICP/MS
Re0.001100ICP/MS
S+0.01%20%ICP
Sb0.1500ICP/MS
Sc1-ICP
Se0.11,000ICP/MS
Sm 0.1100ICP/MS
Sn 1200ICP/MS
Sr0.21,000ICP/MS
Ta0.11,000ICP/MS
Tb0.1100ICP/MS
Te0.1500ICP/MS
Th0.1500ICP/MS
Ti 0.0005%500ICP/MS
Tm0.11,000ICP/MS
U0.110,000ICP/MS
V11,000ICP/MS
W 0.1200ICP/MS
Y0.110,000ICP/MS
Yb0.15,000ICP/MS
Zn 0.210,000ICP/MS
Zr 15,000ICP/MS5,000

Notes: Extraction of each element by Total Digestion is dependent on mineralogy.

Unaltered silicates and resistate minerals may not be dissolved.

UT-6M combines the Total digestion (HF, HClO4, HNO3 and HCl) with analysis by ICP and ICP-MS. Resistate minerals are not digested.

“Near Total” Digestion – ICP

A 0.25g 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 incipient dryness. After incipient dryness is attained, samples are brought back into solution using aqua regia.

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 5000 ppm should be assayed as high levels may not be solubilized. Only sulphide sulfur will be solubilized.

The samples are then analyzed using a Varian ICP-OES. QC for the digestion is 14% for each batch, 5 method reagent blanks, 10 in-house controls, 10 sample duplicates, and 8 certified reference materials. An additional 13% QC is performed as part of the instrumental analysis to ensure quality in the areas of instrumental drift.

“Near Total” Digestion – ICP-MS

Additional elements are determined by ICP-MS on the multi-acid digest solution above. The samples are diluted and analyzed on a Perkin Elmer Sciex ELAN 6000, 6100 or 9000 ICP-MS. One blank is run for every 40 samples. In-house control is run every 20 samples. Digested standards are run every 80 samples. After every 15 samples, a digestion duplicate is analyzed. Instrument is recalibrated every 80 samples.

Elements and Detection Limits (ppm)

Element Detection LimitUpper LimitReported By
Ag0.01100ICP&ICP/MS
Al0.01%50%ICP
As0.210,000ICP/MS
Ba1010,000ICP/MS
Be0.051,000ICP/MS
Bi0.0110,000ICP/MS
Ca0.01%50%ICP
Cd0.021,000ICP/MS
Ce0.01500ICP/MS
Co0.110,000ICP/MS
Cr 110,000ICP/MS
Cs0.05500ICP/MS
Cu0.210,000ICP/MS
Fe0.01%50%ICP
Ga0.0510,000ICP/MS
Ge0.1500ICP/MS
Ge0.05500ICP/MS
Gd 0.15,000ICP/MS
Hf0.1500ICP/MS
In0.005500ICP/MS
Ho 0.11,000ICP/MS
In0.1100ICP/MS
K0.01%5%ICP
La 0.110,000ICP/MS
Li0.5400ICP/MS
Lu 0.1100ICP/MS
Mg0.01%50%ICP
Mn110,000ICP
Mo0.110,000ICP/MS
K0.01%10%ICP
La0.510,000ICP/MS
Li0.210,000ICP/MS
Mg0.01%50%ICP
Mn5100,000ICP
Mo0.0510,000ICP/MS
Element Detection LimitUpper LimitReported By
Na0.01%10%ICP
Nb0.1500ICP/MS
Ni0.210,000ICP/MS
P1010,000ICP
Pb0.510,000ICP/MS
Rb0.110,000ICP/MS
Re0.00250ICP/MS
S+0.01%10%ICP
Sb0.0510,000ICP/MS
Sc0.110,000ICP
Se11,000ICP/MS
Sn 0.2500ICP/MS
Sr0.210,000ICP/MS
Ta0.05100ICP/MS
Te0.05500ICP/MS
Th0.210,000ICP/MS
Ti 0.0005%10%ICP
Tl
0.0210,000ICP/MS
U0.110,000ICP/MS
V110,000ICP/MS
W0.110,000ICP/MS
Y0.1500ICP/MS
Zn 210,000ICP/MS
Zr 0.5500ICP/MS
W 0.1200ICP/MS
Y0.110,000ICP/MS
Yb0.15,000ICP/MS
Zn 0.210,000ICP/MS
Zr 15,000ICP/MS5,000

Notes: Extraction of each element by Total Digestion is dependent on mineralogy.

+ Sulphide sulphur and soluble sulphates are extracted.

If any elements are over-range, an 8-4 Acid Assay can be performed

Assay packages for base metals using 4 acid digestion and ICP-OES or ICP-MS.

Code 8 – 4-Acid ICP-OES Elements and Detection Limits

Element Detection Limit
Ag3 ppm
Cd0.003 %
Co0.003 %
Cu0.001 %
LiLi
Mo0.003 %
Ni0.003 %
Pb0.003 %
Zn0.001 %

Code 8 – 4-Acid ICP-MS Elements and Detection Limits

Element Detection Limit
Ag1 - 10,000 ppm
Bi0.0001 - 1 %
Cd0.0001 - 1 %
Co0.0001 - 1 %
Cu0.0001 - 1 %
Mo0.0001 - 1 %
Ni0.0001 - 1 %
Pb0.0001 - 1 %
Se0.0001 -1 %
Sn0.0001 -1 %
Tl0.0001 -1 %
U0.0001 -1 %
Zn0.0001 - 1 %

Note: Extraction for Total Digestion is dependent on mineralogy