Presentation on sample preparation

1. Determination of Ultra Low Levels of Platinum Group of
Elements in Kimberlites by ICP-MS: Modified
Decomposition Procedure using Double NiS Fire Assay
followed by Te co-precipitation.
Parijat Roy*, Vysetti Balaram, Anil Kumar, Gnaneshwar Rao and Manavalan
Satyanarayan
Email: parijatroy@yahoo.co.in
National Geophysical Research Institute
(Council of Scientific and Industrial Research)

2. INTRODUCTION
Kimberlites
Mantle derived rocks, rare and unusual igneous rocks which are produced during
continental intraplate alkaline magmatism.
Frequently emplaced within or around the margins of ancient cratons and are
important for the range of upper mantle-derived xenoliths and xenocrysts (including
diamonds).
Believed to be derived from deeper levels of the mantle than most other magmas
(Mitchell, 1986; Ringwood et al., 1992; Haggerty, 1994) and the fragments they
incorporate during their passage to the surface provide a direct sample lithospheric
mantle beneath the cratons.
The temperature and the degree of partial melting might play a major role in the
fractionation of the PGEs relative to one another during the extraction of some
magmas from the mantle (Tredoux et. Al, 1986 and Peck and Keays, 1990).
The PGE data from kimberlites and other mantle derived rocks may help to
understand better whether the generation of low partial melt magmas was subject
to similar controls.

3. The restricted nature of the database has prevented detailed modeling of the
geochemical behavior of PGE in Kimberlites.
PGE geochemistry has the potential to provide important information on mantle
processes which are not revealed by other elements (Barnes et al., 1985) and it
might therefore provide an additional insight into kimberlite as well as other
mantle derived rocks geochemistry.
The widely used procedure is the NiS fire assay coupled with a Te coprecipitation
and determination by ICPMS.
PGEs are difficult to determine due to incomplete quantitative extraction from the
host phases, their frequent occurrences as nuggets in sample matrices and with
the exception of ore materials, their low overall concentration in geological
materials.
Only two studies had yet focused on the analysis of trace PGE abundances in
kimberlites (Wilma et al, 2003 and Mc Donald, I. et. al, 1995).
Recoveries of PGEs in these rocks are generally low due to high carbonate and
low silica in typical kimberlites, but it can be enhanced with modified methodology
and analysis by ICP-MS, as tested in this study.

4. OBJECTIVE
There is a great need to develop method for the precise estimates of all PGEs at
extremely low concentration levels in different types of geological materials
including kimberlites.
Key objectives of this study was to develop a method for direct determination of low
(ppt) levels of PGEs from kimberlites, while ensuring high precision and accuracy.
An additional requirement was the need to resolve potential interferences on PGEs
such as Ru, Rh, and Pd arising from the highly incompatible elements (Sr, Rb)
enriched matrix of Kimberlites.
Attempt has been made to determine concentrations of PGE in six samples of
kimberlite from Eastern Dharwar Craton of Southern India for the first time together
with methodology for the determination of the PGEs in kimberlites samples by ICP-
MS after double nickel sulfide fire assay and Te coprecipitation.
Five other standard reference materials viz. JP-1, CHR-Pt, CHR-Bkg, WMS-1 and
WMG-1 were simultaneously analyzed using the same analytical methodology to
access the precision and accuracy of the determinations.

5. Chemical Separation by Double Nickel Sulphide Fire Assay followed by
Single Tellurium Coprecipitation

6. Making of NiS Bead at NGRI laboratory

7. Mass spectrometric measurements and internal standardization
Isotopes Isobars Possible interferents
96Ru(5.54) 96Mo(16.68) 40Ar40Ar(99.6)16º(99.8), 61Ni(1.13)35Cl(75.8), 56Fe(91.72)40Ar(99.6), 80Se(49.9)16º(99.8), 59Co(100)37Cl(24.2)
98Ru(1.86) 98Mo(24.13) 58Ni(68.27)40Ar(99.6), 58Fe(0.28)40Ar(99.6), 82Se(8.9)16º(99.8), 61Ni(1.13)35Cl(24.2), 63Cu(69.2)35Cl(75.8)
99Ru (12.7) 64Ni(0.91)35Cl(75.8), 62Ni(1.13)35Cl(24.2), 64Zn(48.6) 35Cl(75.8), 59Co(100)40Ar(99.6)
100Ru(12.6) 100Mo(9.63) 60Ni(26.1)40Ar(99.6), 65Cu(30.8)35Cl(75.8), 63Cu(69.2)37Cl(24.2), 84Sr(0.56)16º(99.6)
101Ru(17.1) 61Ni(1.13)40Ar(99.6), 64Ni(0.91)37Cl(24.2), 64Zn(48.6) 35Cl(24.2), 66Zn(27.9) 35Cl(75.8), 85Rb(72.16)16O(99.8)
102Ru(31.6) 102Pd(1.02) 62Ni(3.59)40Ar(99.6), 65Cu(30.8)37Cl(24.2), 67Zn(4.1) 35Cl(24.2), 86Sr(9.86)16O(99.6)
104Ru(18.6) 102Pd(11.14) 64Ni(0.91)40Ar(99.6), 64Zn(48.6)40Ar(99.6), 67Zn(4.1)37Cl(24.2), 69Ga(60.11)35Cl(75.8), 88Sr(82.58)16O(99.6)
102Pd(1.02) 102Ru(31.6) 62Ni(3.59)40Ar(99.6), 67Zn(4.1)37Cl(24.2), 65Cu(30.8)37Cl(24.2), 86Sr(9.86)16O(99.6)
104Pd(11.14) 104Ru(18.6) 64Zn(48.6)40Ar(99.6), 64Ni(0.91)40Ar(99.6), 67Zn(4.1)37Cl(24.2), 69Ga(60.11)35Cl(75.8), 88Sr(82.58)16O(99.6)
105Pd(22.33) 65Cu(30.8)40Ar(99.6), 89Y(100)16º(99.6), 68Zn(18.8)37Cl(24.2), 70Ge(20.5) 35Cl(75.8), 70Zn(0.6)35Cl(75.8)
106Pd(27.33) 106Cd(1.25) 90Zr(51.45)16O(99.8), 66Zn(27.9)40Ar(99.6), 69Ga(60.11)37Cl(24.2), 71Ga(39.89)35Cl(75.8)
108Pd(26.46) 108Cd(0.89) 92Zr(17.15)16O(99.8), 68Zn(18.8)40Ar(99.6), 71Ga(39.89)37Cl(24.2), 73Ge(7.8)35Cl(75.8)
110Pd(11.72) 110Cd(12.49) 94Mo(9.25)16O(99.8), 94Zr(17.38)16O(99.8), 75As(100)35Cl(75.8), 73Ge(7.8)37Cl(24.2)
103Rh(100) 63Cu(69.2)40Ar(99.6), 87Rb(27.8416º(99.8), 87Sr(7.00)16O(99.6), 68Zn(18.8)35Cl(75.8), 66Zn(27.9)37Cl(24.2),
191Ir(37.3)
175Lu(97.4)16O(99.8),156Gd(20.5)35Cl(75.8),156Dy(0.06)35Cl(75.8),154Sm(22.7)37Cl(24.2),154Gd(2.18)37Cl(24.2)
193Ir(62.7) 177Hf(18.6)16O(99.8), 158Gd(24.8)35Cl(75.8), 158Dy(0.1)35Cl(75.8), 156Gd(20.5)37Cl(24.2), 156Dy(0.06)37Cl(24.2)
190Pt(0.01) 190Os(26.4) 174Yb(31.8)16O(99.8), 155Gd(14.8)35Cl(75.8), 153Eu(52.2)37Cl(24.2)
192Pt(0.79) 192Os(41.0) 176Yb(12.7)16O (99.8), 176Lu(2.59)16O(99.8),176Hf(5.21)16O(99.8),157Gd(15.7)35Cl(75.8), 155Gd(14.8)37Cl(24.2)
194Pt(32.9) 178Hf(5.21)16O(99.8), 159Tb(100)35Cl(75.8), 157Gd(15.7)37Cl(24.2)
195Pt(33.8) 179Hf(13.6)16O(99.8), 160Gd(21.9)35Cl(75.8), 160Dy(2.3)35Cl(75.8), 158Gd(24.8)37Cl(24.2), 158Dy(0.1)37Cl(24.2)
196Pt(25.3) 196Hg(0.15) 180Hf(35.1)16O(99.8),180W(0.12)16O(99.8), 180Ta(0.12)16O(99.8), 161Dy(18.9)35Cl(75.8),159Tb(100)37Cl(24.2)
198Pt(7.2) 198Hg(10.0) 182W(26.3)16O (99.8), 163Dy(24.9)35Cl(75.8), 161Dy(18.9)37Cl(24.2)
197Au(100) 181Ta(99.99)16º(99.8), 162Dy(25.5)35Cl(75.8),162Er(0.14)35Cl(75.8), 160Gd(21.9)37Cl(24.2)
Isotopic abundances are shown in parentheses.
Isotopes measured are bold and italized.

8. Results and Discussion
Interferences
Interferences from argides and chlorides of Ni and Cu are significant for the light
PGEs (Ru, Pd and Rh).
Kimberlites are particularly enriched in incompatible elements such as Sr, Rb and
Zr, most likely originating from high modal carbonate, apatite and perovskite
abundances. Oxides, nitrides, hydroxides and carbides of these elements cause
extreme interferences (Table) on both 108Pd and 103Rh.
Therefore, isotopes which are least effected by these elements have been chosen
and interference corrections were made.
Though it is not feasible to mathematically correct for interferences on Rh and Pd,
because of variable intensities of Sr and Zr from sample to sample and the ratio of
apparent analyte signal to real analyte signal was extremely large (Pretorius, et. al,
2003),
With matrix removal it is possible to determined directly in natural samples as in this
case specially for kimberlites by Double NiS fire assay method.

9. Internal standard
In order to compensate for signal drift due to changes in nebuliser efficiency,
matrix induced suppressions and enhancement effects(Gray,1986) and for
minimizing mass discrimination and space -charge effects, Cd and Tl were
selected as internal standards because of the close proximity of these masses to
light ( Ru, Rh and Pd) and heavy ( Ir, Pt and Au) PGEs respectively.
It has been found that the concentration of these elements were found to be
insignificant (< 30 ngg-1) in the samples investigated. Very close agreement (<
2%) of values obtained by using different isotopes for Ru, Pd, Ir and Pt
demonstrates that the interferences effects by matrix elements are not
significant.
Linear calibration curves were obtained for all elements from the calibration
standards WMG-1 and WMS-1.
Several loss of signal due to cone deposition was reduced to tolerable levels
without compromising detection limits by increasing the wash times between
sample to 10 min. A wash with 4% aqua regia between samples also reduces
background memory effects, particularly for Ir (Pretarious, W. et.al, 2003).

10. Accuracy and Precision
To monitor the recoveries of PGEs in kimberlite samples (10g), five reference
materials JP-1, CHR-Pt, CHR Bkg, WMS-1 and WMG-1, 5g each in triplicates and
digested in the same manner as described in the procedure.
The accuracy of the results presented in these studies can be seen in Table and Fig.
Analyte WMS-1(2) WMS-1(1) CV CHRBkg(2) CHRBkg(1) CV JP-1(2) JP-1(1) CV
Ru 0.096±0.004
0.093±0.00
3 0.099
0.076±0.00
3 0.062±0.002 0.067
0.005±0.0
00 0.004±0.000 0.005
Rh 0.211±0.007
0.210±0.00
7 0.225
0.011±0.00
0 0.01±0.00 0.009 0.00096
0.0008±0.000
0 0.0009
Pd 1.166±0.045
1.157±0.05
6 1.185
0.062±0.00
5 0.061±0.003 0.07
0.0014±0.
000
0.0009±0.000
0 0.0013
Ir 0.259±0.010
0.215±0.00
6 0.235
0.031±0.00
1 0.03±0.00 0.028
0.0056±0.
0002 0.003±0.001
Pt 1.687±0.099
1.690±0.06
4 1.741
0.067±0.00
3 0.06±0.00 0.05
0.0044±0.
000 0.004±0.001 0.0049
Au 0.259±0.008
0.263±0.01
0 0.279
0.032±0.00
1 0.026±0.000 0.028
0.0001±0.
000
0.0001±0.000
1 0.0002
(2) Double NiS Fire Assay, (1) Single NiS Fire Assay

11. Analyte WMG-1(2) WMG-1(1) CV CHR-Pt+(2) CHR-Pt+(1) CV
Ru 0.033±0.001 0.032±0.00 0.035 8.62 8.58 9.2
Rh 0.02±0.00 0.02±0.00 0.026 4.31 4.48 4.7
Pd 0.311±0.016 0.323±0.001 0.282 72.65 73.55 80.8
Ir 0.052±0.002 0.0514±0.002 0.046 5.48 6.12 6.2
Pt 0.758±0.042 0.762±0.034 0.731 52.68 53.21 58
Au 0.092±0.003 0.10±0.002 0.11 4.1 4.15 4.3
Analyte
P-2 (i)
(2)
P-2 (ii)
(2)
P-2(ii)
(1)
P-7
(2)
CC-4B
(2)
CC-4B
(1)
CC-5
(2)
KL-4B
(2)
KL-3
(2)
KL-3
(1)
Ru
0.0036 0.0064 0.0024 0.0016 0.004 0.003 0.0038 0.0034 0.003 0.0018
Rh
0.0006 0.001 0.0004 0.0002 0.0004 0.0001 0.0002 0.0004 0.0002 0.0002
Pd
0.018 0.0396 0.02 0.0058 0.0256 0.0096 0.0084 0.0106 0.0112 0.0104
Os
0.0012 0.0026 0.0014 0.0002 0.0026 0.0012 0.001 0.0008 0.002 0.001
Ir
0.002 0.0022 0.0012 0.0002 0.0036 0.0016 0.0016 0.0008 0.0032 0.0026
Pt
0.017 0.037 0.015 0.0024 0.0126 0.0073 0.0044 0.007 0.0066 0.0052
Au
0.0164 0.0051 0.0032 0.0048 0.007 0.005 0.0242 0.017 0.0052 0.0041
(2) Double NiS Fire Assay, (1) Single NiS Fire Assay
(2) Double NiS Fire Assay, (1) Single NiS Fire Assay

12. WMS-1
-10
-5
0
5
10
15
Ru Rh Pd Ir Pt Au
Double NiS Fusion Single NiS Fusion Certified Values
CHRBkg
-20
-10
0
10
20
30
40
Ru Rh Pd Ir Pt Au
Double NiS Fusion Single NiS Fusion Certified Values
WMG-1
-40
-30
-20
-10
0
10
20
Ru Rh Pd Ir Pt Au
Double NiS Fusion Single NiS Fusion Certified Value
JP-1
-60
-50
-40
-30
-20
-10
0
10
20
Ru Rh Pd Ir Pt Au
Double NiS Fusion Single NiS fusion Certified values
CHR-Pt+
-20
-10
0
10
20
Ru Rh Pd Ir Pt Au
Double NiS Fusion Single NiS Fusion Working Values
Deviation of obtained values in these studies from the working values.

13. 0.000
0.001
0.010
0.100
1.000
Ir Ru Rh Pt Pd
P2(2)
P-7
CC-4
KL-4
KL-3
KL-3 B
Chondrite-normalised pattern obtained for Southern Indian
Kimberlites after Double NiS fire assay method.

14. Conclusions
 The modified preconcentration method of double NiS fire assay followed by
single Te coprecipitation is very effective for the determination of ultra low level
PGEs in kimberlite samples.
 The error limits were found to be within 5 % for most of the elements. The
accuracy and precision achieved was < 6% RSD in most cases, which suggests
that the PGE data obtained for kimberlites are suitable for geochemical
interpretations.
 This study illustrates the importance of the decomposition step when analysing
for PGEs in geological materials by ICP-MS.
 The proposed method for the determination of PGEs in geological samples is
suitable for an analytical laboratory where analysis of low concentrations of
PGEs is necessary.

15. This method is also suitable for the determination of low levels of PGEs in
other geological samples but, more detailed studies have to be carried out
depending on the matrix composition.
The procedure is reliable and comparatively easier.
Still further efforts and research has to be carried out for these particular types
of rock kimberlites and other mantle derived rocks for the estimation of PGEs
to understand better the internal processes with in earth.

17. Acknowledgements
1. I am Grateful to AOGS organizers for providing me this
platform to present my work.
2. I am thankful to my Guide and Supervisor Dr. V. Balaram
for his constant support and guidance.
3. I am thankful to CSIR for providing me funding.
4. I am also thankful to Director NGRI for supporting me to
come here and present my work.