1. Analysis of High Purity Zinc by Glow Discharge Mass Spectrometry for Use in Thermometry
T. Gusarova, B. Lange, H. Kipphardt, R. Matschat and U. Panne
Federal Institute for Materials Research and Testing (BAM)
Working Group “Primary Calibration Materials; Trace Analysis”
Physikalisch-Technische Bundesanstalt
Federal Institute for Materials Research and Testing

2. Content PTB + BAM co-operation work
GD-MS: basic principles, advantages and limitations
Calibration with pellets (sample preparation)
Calibration with Zinc Certified Reference Materials
Pure zinc samples, used in thermometry
Conclusions
Prospects

3. Trace element mass fraction
Co-operation work
Trace element mass fraction
Temperature
PTB and BAM:
joint development of a basis for creation of fix points
based on certified pure materials
taking into account national and international regulations
estimating corresponding uncertainty
Solid state
Ultra-high purity materials
Multielement ultra-trace determination (μg/kg, ng/kg)
Method traceable to SI –precondition for certification of RM

4. Glow Discharge Mass Spectrometry (GD-MS)
Multielement
Solid sampling
No sample preparation
No losses of analytes
No chemical contamination of the sample
Less time is needed
Decreased non-spectral Interferences (compared to ICP-MS)

5. Main advantages of Finnigan ELEMENT GD (Thermo Fisher Scientific)
(with Sample Holder)
GD Ion Source
Ion Transfer Optics
ESA
SEM
Faraday Cup
Detection System
Magnet
Grimm-type ion source
High sputter rate, short analysis time
High sample throughput (6 Samples per hour)
More than 12 orders of magnitude automatic detection system
Complete determination of matrix and trace elements (up to ng/kg)
Extremely high SBR (Signal to Background Ratio)
Double focussing mass spectrometer (Resolution up to 10000)

6. Calibration with doped pellets
Quantification with Element GD
Semiquantitative
Quantitative
Traceable to SI
IBR
Direct
Indirect
Standard RSF
RSF
Calibration with doped pellets
Calibration with RM

7. Preparation of Zn Pellets by wet doping
52 elements
1% HNO3
Mixing
shaking in 3 dimensions of space
Pressing ~ 1 g of the powder in pellets into a sample steel ring under 90 kN/cm2
Sample diameter ≈ 12 mm
Thickness ≈ 2 mm
Analysing

8. Observation of intensity-time behaviour of different elements
Doped with powders: grain size between 3 and 900 μm
123Sb 70 μm
10 ppm
58Ni 3-7 μm
1 ppm
56Fe > 840 μm
50 ppm
Doped with liquids
24Mg
5 ppm
64Zn
matrix
114Cd
5 ppm
Pre-sputter time
Measurement time
Pre-sputter time
Measurement time
Pre-sputter time
Measurement time

9. Mass fractions of trace elements in the pellets
Analysing data
Mass fractions of trace elements in the pellets
10 mg/kg; 5 mg/kg; 1 mg/kg; 500 µg/kg; 100 µg/kg; 50 µg/kg; 10 µg/kg; 5 µg/kg; blank
Zn powder 99,999% pure <150 micron
Parameters
Voltage ~500 V
Current 20 mA
Ar Gas Flow 375 ml/min
Peltier Cooling 20 °C
Low Resolution (LR) ≈ 400
Medium Resolution (MR) ≈ 4000
High Resolution (HR) ≈ 10000

10. Calibration with doped pellets

11. Calibration with doped pellets

12. Trace element mass fraction in mg/kg
Zn Certified Reference Materials
Voltage ~500 V
Current 20 mA
Ar Gas Flow 375 ml/min
Peltier Cooling 20 °C
Trace element mass fraction in mg/kg
± uncertainty mg/kg

13. CRMs measurements

14. Procedure for samples analysis
Scanning (6 – 239 u) ↓
elements of interest
Pellet preparation
114Cd
112Cd
116Cd
111Cd
113Cd
38Ar40Ar40Ar
Compiling of measurement method and parameter optimisation
Calibration of Element GD with pellets
Sample measurements

15. Comparison of materials for thermometric use
PTB-Zn1 and PTB-Zn2a can be easily distinguished. That might also be visible in the temperature measurements
Limits of detection (6s) for most of the elements are < 1 mg/kg (many of them go down to µg/kg level)
These limits of detection could be in future improved with enhancement of the sensitivity of the method by special calibration of detection system and other measures.

16. Analysis of In In-Sample in sample holder
Light optical microscope image

17. Enhancement of signal sensitivity of
Glow Discharge Optical Emission Spectroscopy
Titanium in pure copper
Flat sample
Sample with a hole
a.u.
a.u.
mass fraction, mg/kg
mass fraction, mg/kg

18. Conclusions
Pellets doped with solutions can be successefully used for the calibration of GD-MS
It is the most accurate calibration procedure to obtain small uncertainty (compared to factor 2 or even more uncertainty by use of RSF approach)
In this way direct traceability of the measurement results to SI is achieved – this procedure is a precondition for the certification of reference materials (CRMs) with GD-MS
CRMs of pure zinc were also measured. The measurement results were in good agreement with the calibration curves of Zn-pellets
A procedure for the analysis of materials used for fix-point cells is being worked out
Two samples of fix-point materials from different producers were compared
First investigations with In samples were carried out
Another analytical techniques such GD-OES will be improved and tried to be used for the analysis of the fix-point materials

19. Prospects
Preparation of doped In-pellets and calibration for In matrix
Analysis of the material for fix-points-cells
Graphite analysis
Comparison of analyses with ICP-MS, LA-ICP-MS, GD-OES and GD-MS
Determination of non-metallic elements (O, S…)
Expansion of GD-MS to analysis of other materials

20. Thank you for your attention
Thank you for financial support …
Dr. Fischer, J.
Dr. Rudtsch, S.
Fahr, M.
Dr. Lange, B.
Dr. Hodoroaba, V.-D.
Dr. Kipphardt, H.
Dr. Matschat, R.
Prof. Dr. Panne, U.
… and help during investigations!
BAM Division I.1
Richard-Willstaetter-Strasse 11
12489 Berlin, Germany
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