LBMA Proficiency Testing

Transcription

1 LBMA Proficiency Testing Jonathan J. Jodry Metalor Technologies SA, Switzerland LBMA Assaying and Refining Conference March 2017, London

2 Topics What is a Proficiency Testing? Sample composition, Participation, Z-scores Detailed results, Issues Statistics, Corrective actions Conclusion

3 What is a Proficiency Testing? Also called Interlaboratory testing or Round robin Homogeneous material analysed by multiple laboratories Comparison of results obtained on an anonymous basis Z = 3 Z = 2 Z = 1 Reference Z = -1 Z = -2 Z = -3 Z-scores definition : Reference = mean of all valid results Z = 1 for (fixed by LBMA)

4 Why Join a Proficiency Testing validating new analytical methods discovery of method sensitivity planning for equipment and training detection of (systematic) errors requirement of ISO standard assessing performance and capabilities of staff analysing different samples compare performance with competitors

5 Composition 6 years of Au PT From 995 to Classic impurities : Ag, Cu, Pt, Pd In 2017 : Zr added First year for Ag PT Pd-Au-Pt Other Cu Pd Pt Ag Other Cu Pd Pt Au

6 Participation & Results Number of laboratories joining the PT non-gdl participants : Ag Z-score 100% 80% 60% 40% 20% -2 < Z <2 2 < Z < 3 Z > 3 0%

7 ISO accredited (GD) ISO accredited (non-gd) non accredited (GD) non accredited (non-gd) Reference 2017 Ag Detailed Results '04 '05 '35 '16 '45 '26 ' '06 '20 '52 '34 '38 '50 '07 '41 '42 '13 '28 '53 '17 '27 '30 '43 '01 '09 '15 '40 '32 '54 '49 '12 '25 '08 '03 '14 '21 '11 '19 '24 '33 '48 '31 '02 '23 '39 '47 10 labs out of 49 (20%) would have failed GDL application (+/ ) 5 labs did not submit average value! '10

8 2017 Ag Detailed Results Non-Spectroscopy Non-Spectroscopy (non-gd) titration '04 titration Spectroscopy (difference) ' Spectroscopy (difference, non-gd) ' Reference SPARK '16 '45 '26 ' '10 gravimetry '06 '20 '52 SPARK '34 '38 '50 '07 '41 '42 '13 '28 '53 '17 '27 '30 '43 '01 '09 '15 '40 '32 '54 '49 '03 '14 '21 '24 '33 '12 '25 '08 '11 '19 '48 '31 '02 '47 '23 '39 SPARK titration SPARK Non-Spectroscopy methods (titration, fire assay, gravimetry) are not robust enough

9 ISO accredited (GD) ISO accredited (non-gd) non accredited (GD) non accredited (non-gd) Reference 2017 Au Detailed Results '06 '27 '31 '33 '41 '22 '55 '58 '12 '46 '15 ' '50 '47 '07 '18 '36 '49 '45 '42 '34 '03 '05 '16 '60 '02 '37 '39 '21 '04 '14 '25 '26 '08 '01 '09 '38 '23 '19 '35 '29 '40 '11 '43 '13 '10 '28 '17 '48 '24 '51 '53 '59 '20 '54 ' '32 '57 '56 17 labs out of 60 (28%) would have failed GDL application (+/ ) Significant and abnormal bias toward higher titles

10 995.6 Fire Assay 2017 Au Detailed Results Fire Assay (non-gd) '46 ' Spectroscopy (difference) Spectroscopy (difference, non-gd) '31 '33 '41 '22 '55 '58 ' Reference '06 '27 ' '50 '47 '03 '07 '18 '36 '49 '45 '42 '34 '16 '60 '02 '37 '39 '04 '14 '05 '21 '25 '29 '40 '13 '10 '11 '43 '28 '23 '19 '17 '35 '48 '24 '08 '51 '53 '01 '59 '09 '20 '54 '38 '30 ' '32 '57 '56 More than 50% of issues are with spectroscopy! 6 labs did not identify the presence of Zr in the sample 7 GD labs would have qualified this material as 995+

11 995.6 Fire Assay 2017 Au Detailed Results Fire Assay (non-gd) '46 ' Spectroscopy (difference) Spectroscopy (difference, non-gd) '31 '33 '41 '22 '55 '58 ' Reference '06 '27 ' '50 '47 '03 '07 '18 '36 '49 '45 '42 '34 '16 '60 '02 '37 '39 '04 '14 '05 '21 '25 '29 '40 '13 '10 '11 '43 '28 '23 '19 '17 '35 '48 '24 '08 '51 '53 '01 '59 '09 '20 '54 '38 '30 ' '32 '57 '56 Comment from lab 003: We decide to perform an additional ICP-OES analysis because the fire assay result was < 995. ICP-OES analysis is perfectly aligned with the fire assay and ( ) we found 518 ppm of Zr

12 ISO accredited (GD) ISO accredited (non-gd) non accredited (GD) non accredited (non-gd) Reference 2016 Au Detailed Results '23 '2 '12 ' '18 '60 '51 '37 '34 '4 '9 '30 '40 '57 '15 '7 '14 '33 '44 '49 '52 '59 '62 '39 '58 '5 '8 '17 '42 '43 '46 '47 '24 '26 '38 '63 '64 '6 '13 '28 '35 '55 '56 '22 '27 '31 '10 '21 '11 '36 '50 '16 '25 ' '3 '48 ' '29 Good overall performance '53

13 2016 Au Detailed Results Fire Assay Fire Assay (non-gd) Spectroscopy (difference) Spectroscopy (difference, non-gd) Reference '12 '45 '2 ' '29 '3 '48 '1 '4 '9 '30 '40 '57 '15 '7 '14 '33 '44 '49 '52 '59 '62 '39 '58 '5 '8 '17 '42 '43 '46 '47 '24 '26 '38 '63 '64 '6 '10 '21 '22 '27 '11 '13 '28 '35 '55 '56 '36 '25 '54 '16 '50 '31 Ag by AAS Good overall performance '18 '60 '34 '51 ' '53

14 Fire Assay vs ICP-OES FA ICP After reprocessing (2016 removing NG labs; 2017 removing Zr issue labs) : FA ICP Results normalised to 1000

15 ICP-OES Uncertainty of ICP-OES is proportional to element concentration Ag (2014) Cu (2014) Ag (2016) Ag (2017) Mean St. Dev St. Dev. % 3.7% 2.1% 2.5% 3.6% 200 St. Dev. 4.0% St. Dev. [mg/kg] St. Dev. % 3.0% 2.0% 1.0% St. Dev. % 0 0.0% Impurity [mg/kg]

16 How to react to a bad Z-score So you received your lab performance Z-score out of the -2 to +2 area? PT is about learning and improving, not passing or failing Don t Hide the result to your staff / auditors / quality staff / management Assume the issue is not important or will be taken care of by someone Limit investigation at the first problem identified Do Study results in detail - mean value - standard deviation - false positive for impurities - error on specific impurities

17 How to react to a bad Z-score So you received your lab performance Z-score out of the -2 to +2 area? PT is about learning and improving, not passing or failing Don t Hide the result to your staff / auditors / quality staff / management Assume the issue is not important or will be taken care of by someone Limit investigation at the first problem identified Do Study results in detail Identify all possible sources of problems: Preparation, Method, Equipment, Calculation, Reporting Root cause investigation: Investigate, Implement corrective actions, Execute analysis, Control effectiveness Adapt your methods or procedures, inform and train staff Participate next year and see how much you improved!

18 Danger of Synthetic Samples PT supervised by Referee Committee (composition, preparation) Goal is: Cover the whole 995 to range Composition not too simple (e.g. Au-Ag binary), not too complex No exotic element Samples are specifically prepared for PT Those samples are however NOT real-life materials Risk is: Not having impurities which can be found in the refineries Oversimplifying the compositions Creating a false sense of comfort Usually, real factory samples lead to worse results than PT samples!!

19 Conclusions Two years ago Future of PT Au : Different compositions Improvement of spectroscopic methods for Au 995 Increase participations of non-gd laboratories New methods (MP-AES, ICP-MS, ) Ag PT For next two years Improvement of the laboratory performances Significantly lowering outliers laboratories More complex samples (!)

20 Conclusions Please help improving the PT Submit everything requested (enough replica, mean) Answer clearly ISO accreditation question Give clearly the name of the method used for measurement, e.g. ICP- OES, Fire Assay or Gravimetry, not Spectroscopy or By difference Use the comment box to describe combined methods Thanks to LBMA staff and former staff, especially Neil Harby, Varsha Peiris, Ruth Crowell and Stewart Murray FAPAS All my referee colleagues