Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine

doi:10.1016/j.apradiso.2004.01.007

Applied Radiation and Isotopes

Volume 60, Issue 5, May 2004, Pages 629-633

https://doi.org/10.1016/j.apradiso.2004.01.007 Get rights and content

Abstract

The applicability of inductively coupled plasma-mass spectrometry (ICP-MS) for determining actinides in urine was investigated. Performances of ICP-MS including detection limit and analysis time were studied and compared with α spectrometry performances. In the field of individual monitoring of workers, the comparison chart obtained in this study can be used as a guide for medical laboratories to select the most adequate procedure to be carried out depending on the case in question (the radioisotope to be measured, the required sensitivity, and the desired response time).

Introduction

Monitoring of workers occupationally exposed to a risk of contamination with radioactive material is generally based on workplace monitoring (measurements of airborne radioactivity in the workplace for example) and on individual monitoring. The individual monitoring can be achieved through in vivo measurements (anthroporadiametry) and in vitro measurements (in urine and faeces) (ISO standard 12790-1, 2002). In case of contamination with α-emitting actinides, in vivo measurement offers a very poor sensitivity mainly due to the low energy and intensity of X-ray photons emitted and attenuation by the tissues (Toohey et al., 1991). Consequently, detection of actinides contamination is mainly based on in vitro measurements, i.e., excreta analyses.

The analysis of actinides in urine is based on their measurement by α spectrometry. This technique requires lengthy chemical purification procedures, in particular the mineralisation of the urine sample to limit the self-absorption of α-particles and the separation of each actinide to avoid spectral interferences. In addition, long sample counting times (several days) are necessary to reach detection limits which respect the legal requirements.

The development in the last decades of inductively coupled plasma-mass spectrometry (ICP-MS), a multielement technique, has made this analytical tool a powerful technique with high sensitivity and low detection limits (Stuewer and Jakubowski, 1998). The main advantage of ICP-MS compared to α spectrometry is that the measurement time is considerably shortened (10 min), and this technique is well suited for analysis of liquid samples such as urine. In addition, it was demonstrated that ICP-MS is a valuable technique for the determination of long-lived radionuclides (Caddia and Iversen 1998; Baglan et al (1999), Baglan et al (2000), Baglan et al (2001)).

The aim of the present work is to assess to which extent the ICP-MS technique can be an alternative to α spectrometry for actinides measurement in urine, in terms of detection limit and analysis time. To achieve this goal, the detection limits obtained by ICP-MS for different actinides were calculated after urine dilution, but also after a chemical purification of the urine sample. The calculated results were compared to the α spectrometry detection limits. Thus, the potentialities of ICP-MS can be determined in function of the radioisotope to be analysed, the required sensitivity, and the desired analysis time.

In addition to these metrological considerations, the choice of the analytical procedure to be carried out for actinide determination in urine is also discussed according to the case in question within the context of individual monitoring of workers.

Section snippets

Instrumentation

ICP-MS measurements were performed with a quadrupole mass spectrometer “Plasmaquad PQ2+” (THERMO ELEMENTAL). The solution is pumped by a peristaltic pump (GILSON Minipuls 3) and the nebuliser is of the Meinhardt type. The aerosol produced is directed through a “Scott” water-cooled spray chamber into a quartz plasma torch.

For α spectrometry measurements, ALADIN-type α-spectrometers, with Passivated Implanted Planar Silicon detectors (Eurysis Mesures, France) were used.

Analytical procedures

To assess the performances

Results

, , are used to calculate the detection limits obtained for each analytical procedure, with a 95% confidence level.

(i)
α spectrometry detection limits (Rapport CEA, 1983) $DL (mBq l^{−1})= 5.66 B eR_{c} tV,$ where B is the background counts, e the counting efficiency of the detector (%), R_c the chemical recovery (%), t the counting time (s) and V the urine volume (l).
A counting efficiency of 25%, a chemical recovery of 80% (average yield), a counting time of 3 days, and a urine volume of 1 l are used to calculate

Discussion

The three straight lines in Fig. 2 represent the detection limits of each analytical procedure. For α spectrometry, the detection limit is not a function of the radioisotope half-life. A DL value of 0.2 mBq l⁻¹ (log DL=−0.7) has been chosen, which corresponds to a counting time of about 3 days. This value is currently reached for low level measurements, but it is obvious that for different counting times a translation of the DL straight line will be observed. The straight line (plots ●) represents

Conclusion

This work shows the performances of ICP-MS for actinides determination in urine. For isotopes with T_1/2⩾5×10⁴ years, ICP-MS is well suited and an excellent alternative to α spectrometry, and in addition a more competitive technique, especially in terms of response time. ICP-MS is particularly competitive for uranium determination.

The chart presented in this paper shows the influence of three parameters: the radioisotope to be analysed, the level of activity to be measured, and the required

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Potentialities of mass spectrometry (ICP-MS) for actinides determination in urine

Abstract

Introduction

Section snippets

Instrumentation

Analytical procedures

Results

Discussion

Conclusion

Implementation of ICP-MS protocols for uranium urinary measurements in worker monitoring

Health Phys.

On the use of ICP-MS for measuring plutonium in urine

J. Radioanal. Nucl. Chem.

Determination of 232Th in urine by ICP-MS for individual monitoring purposes

Health Phys.

Determination of 237Np at trace level; evaluation of various analytical procedures

Radiochim. Acta

Validation of uranium determination in urine by ICP-MS

Health Phys.

Determination of uranium in urine by inductively coupled plasma mass spectrometry with pneumatic nebulization

J. Anal. At. Spectrom.

Determination of ²³²Th in urine by ICP-MS for individual monitoring purposes

Determination of ²³⁷Np at trace level; evaluation of various analytical procedures