analysis of gold 995‰ via different methods 2019/2b. assaying - daniela manara and... ·...

An MKS PAMP GROUP Company

The Eighth LBMA Assaying & Refining Conference, Royal Garden Hotel, Kensington, London, 17-20 March 2019

ANALYSIS OF GOLD 995‰ VIA DIFFERENT METHODSpresented by Daniela Manara and Barbara Badiello

PAMP

Selecting a method: the key factors

2

The selection of an analytical method is based on several key factors

Equipment

Sample preparation

Certified reference material

Skills

Costs

Uncertainty

Analysis of Gold 995 ‰ via different methods – The Eighth LBMA A&R Conference, London, 17-20 March 2019

PAMP

Our study is based on an inductive approach

The methodology: a study based on real data available

3

DEDUCTION

CONFIRMATION

OBSERVATION

COMPARISON

INDUCTION

COMPARISON

PATTERN

OBSERVATION


PAMP

Steps and objectives

4

Overview1

Comparison2

Evaluation3

Focus on instrumental conditions

No theory on spectroscopy

Focus on statistical conditions

No introduction on statistics

Interpretation of the results


PAMP

The range of methods available: main PROs and CONs

5

METHOD ADVANTAGES DISADVANTAGES

SPARK - OES• Time• Morphology• Uncertainty

• Indirect analysis• Certified reference material• Line range

ICP OES• Certified reference material• Line range

• Indirect analysis• Preparation• Time

WD XRF• Line range• Non-destructive• Uncertainty

• Certified reference material• Morphology• Indirect analysis

FIRE ASSAY• Direct analysis • Time

• Skills


PAMP

The methods available at PAMP

6

Fire assay

Nabertherm

ISO17025 accredited

SPARK OES

Ametek Labm / Labs

ISO17025 accredited

ICP OES

Agilent Varian 720 ES

Interlaboratory tested

WD XRF

Thermo ARL Advant’XP

Interlaboratory tested


PAMP

The dataset

7 Analysis of Gold 995 ‰ via different methods – The Eighth LBMA A&R Conference, London, 17-20 March 2019

PAMP

Results analysis

8

Check of normal distribution?

Elimination of outliers?

Analysis of variance (ANOVA)?

Principal component analysis (PCA)?


PAMP

All data in the dataset confirm a normal distribution

Results analysis

9

Check of normal distribution

Elimination of outliers?




PAMP

3,7% outliers removed from the dataset


Results analysis

10


Elimination of outliers



1700.0

1800.0

1900.0

2000.0

2100.0

Ag

2700.0

2750.0

2800.0

2850.0

2900.0

2950.0

3500.0

3600.0

3700.0

3800.0

SPARK - LABS WD XRF ICPSPARK LABM

Discrepancy

Discrepancy

No discrepancy


PAMP

There is no significant difference between groups

3,7% outliers removed from the dataset


Results analysis

11


Elimination of outliers

Analysis of variance (ANOVA)


Au

Ag

Cu

Test for equal means

Sum of sqrs dfMean square F

p (same)

Betweengroups 0.0549767 3 0.0183256 0.02425 0.9949

Withingroups 87.6689 116 0.755767

Permutation p (n=99999)

Total 87.7239 119 9.95E-01

Kruskal-Wallis test for equal medians

H (chi2): 0.2459

Hc (tie corrected): 0.246

p (same): 0.9699

There is no significant difference between sample medians


Sum of sqrs dfMeansquare F

p (same)

Betweengroups 96628.6 3 32209.5 0.06156

9.80E-01

Withingroups 5.34E+07 102 523228


Total 5.35E+07 105 0.9801


H (chi2): 0.3741


p (same): 0.9455



Sum of sqrs dfMean square F

p (same)

Betweengroups 21137.3 3 7045.77 1.292 1.281

Withingroups 589087 108 5454.51


Total 610224 111 0.2773


H (chi2): 5.394


p (same): 0.9451



The dataset can be used for furtheranalysis adding new variables

PAMP

Results analysis – Principal Component Analysis (PCA) /1

12

Three new variables are introduced

Frequency of use for each method1

Skills needed (training investment needed)2

Time needed for the analysis3


PAMP

Results analysis – Principal Component Analysis (PCA) /2

13

PC Eigenvalue % variance

1 489.201 99.429

2 2.03626 0.41386

3 0.699681 0.14221

4 0.0715112 0.014534

PC 1 PC 2 PC 3 PC 4

Au 0/00 -0.010 0.992 1.000 0.001

Time 1.000 -0.001 0.000 0.000

Use frequency -0.682 0.113 -0.004 0.722

Skill 0.995 0.037 0.000 0.062

The method choice is directly influencedby the duration of the analysis (mainly)

and by the skills required

The frequency of use is indirectly

proportional to Time and Skills required

Fineness is not influencedby method selection

The most used method is the less time-intensive The less time-intensive method is the one requiring less

training time The results delivered by each method are equivalent

PCA interpretation


PAMP

Conclusions

14 Analysis of Gold 995 ‰ via different methods – The Eighth LBMA A&R Conference, London, 17-20 March 2019

In addition to fire assay, spectrometry offers a wide range of technical options in analysing high grade gold

Precision was not compared in this study, as only average values are consideredAdding this parameter in the dataset could lead an interesting additional analysis

The cost for each analysis could also be an interesting variable to compare and correlate with others

Our goal, with the results of this work, is to provide the «spark» towards further study on the impact and opportunity of merely organisational&managerial parameters on analytical methods selection

An MKS PAMP GROUP Company

Thank youThe Eighth LBMA Assaying & Refining Conference, Royal Garden Hotel, Kensington, London, 17-20 March 2019

analysis of gold 995‰ via different methods 2019/2b. assaying - daniela manara and... ·...

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