1. ANALYSIS OF ULTRATRACE LEVELS OF URANIUM AND THORIUM BY MASS SPECTROMETRY
M. Fernández, E. Conde, A.I. Barrado
Department of Technology
Department of the Environment

2. 2. CONCENTRATION MEASUREMENT
ANALYSIS OF ULTRATRACE LEVELS OF URANIUM AND THORIUM BY MASS SPECTROMETRY
Overall Process
1. SAMPLE TREATMENT
The processes involved in this phase and their need depend on the measurement technique
 MATRIX DECOMPOSITION
 DISOLUTION
 MATRIX ELIMINATION
Ion exchange
Coprecipitation
Liquid-liquid extraction
Contribution from reagents to background :
Detection limit increase
Uncertainties in the ICP-MS results.
2. CONCENTRATION MEASUREMENT
To consider
 RADIOMETRIC TECHNIQUES: α-spectroscopy, γ- spectroscopy,
and neutron activation analysis (NAA)
 MASS SPECTROMETRY

3. MASS SPECTROMETRY MASS SPECTROMETRY TECNIQUES
INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY
Basic Principles
Instrumentation
Relevant characteristics

4. MASS SPECTROMETRY
Instrument scheme

5. MASS SPECTROMETRIC TECNIQUES APPLIED TO RADIOPURITY ANALYSIS
GLOW DISCHARGE PLASMA MASS SPECTROMETRY (GD-MS)
Direct analysis of solid samples can be advantageously performed, without chemical sample preparation. The sample functions as the cathode of the discharge, making this approach particularly suitable for the analysis of high-purity metals.
INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (ICP-MS)
ICP-MS offers sub pg/ml detection limits for U and Th with minimal analysis time. However, one of the main limitations of this technique is the need for sample preparation prior to analysis.

6. INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY (ICP-MS)

7. ICP-MS: INSTRUMENTATION
Detector
Torch
Interface
Nebulizer
ICP-MS Element XR (Thermo Scientific)

8. ICP-MS: RELEVANT CHARACTERISTICS
Schematic representation of processes in ICP-MS from sample introduction to mass analysis
• Most elements possible (around 80)
• Elemental and isotopic information given
• Concentration range ppq (pg/L) to mid-ppm (100s mg/L)
• Rapid analysis – 2-6 minutes per sample
• Good precision – ~2% RSDs
Mass of element
Signal intensity

9. ANALYSIS OF POLYETHYLENE
SAMPLE TREATMENT
Dissolution
ICP-MS MEASUREMENT
RESULTS

10. Acid Sub-boiling purification system
SAMPLE TREATMENT
CLEANROOM ISO 6 (Class 1000)
 CH2  CH2 n SAMPLE
550 ºC, 1 h
Residue
+ 1 ml HNO3
+ 1 ml H2O
Muffle
Evaporation
IR lamp
US bath
+ 4 ml H2O
ICP-MS MEASUREMENT
Pt crucible
Acid Sub-boiling purification system

11. RESULTS: Spectra
INSTRUMENTATION: High resolution ICP-MS Element XR (Thermo Scientific) with double focusing reverse Nier-Johnson geometry and SEM/Faraday detectors
232Th
238U
230Th
235U
8000 cps
14000 cps
238U
232Th
Signal intensity (counts per second, cps)
230Th
235U
Mass of detected isotopes
Mass of detected isotopes
Fig 1. Background of dissolution proccess
Fig 2. Sample of polyethylene
Prior to sample treatment, five “blanks” were procesed in the same crucible, in order to evaluate all possible contributions to background (Figure 2).

12. RESULTS: Quantification Limit of detection (ng/ml)Th U
0,000710
0,000250
Prudnikov - Fresenius J Anal Chem (1998) 362 : 465–468
Polyethylene sample
Th (ng/ml) sol
Th (ng/g) sample
U (ng/ml) sol
U (ng/g) sample
0,00379
0,00260
0,00558
0,00383