Baki Sadi

A rapid bioassay method for the determination of 90Sr in human urine sample.

A rapid bioassay method has been developed for the determination of (90)Sr in human urine samples. The method is based on on-cartridge decolourisation of urine sample, separation of (90)Y from (90)Sr on an anion exchange resin column and by determination of (90)Sr using a liquid scintillation analyser (LSA). Separation of (90)Y from (90)Sr was achieved through selective complexation of yttrium with phosphate and subsequent retention of the anionic yttrium phosphate species on anion exchange resin. A total recovery of 97 +/- 2 % was obtained for strontium with three washes. The minimum detectable activity for the method was 0.2 Bq or 40 Bq l(-1). Measurement accuracy (relative bias, B(r)) and repeatability (relative precision, S(B)) of the method for the determination of (90)Sr were found to be -1 and 4.7 %, respectively. Excellent linearity (r(2) > 0.999) was established over an activity range from 3.25 x 10(2) to 3.25 x 10(4) Bq l(-1). The method was also found to be very robust (S(B) < 5 %) against the matrix effect from different urine samples. Performance of the rapid bioassay method for sensitivity, accuracy and repeatability evaluated against the performance criteria for radiobioassay (ANSI N13.30) was found to be in compliant. Considering the simplicity, excellent analytical figures of merit, fast sample turnaround time (<1 h) and cost efficiency (<30 USD per sample) of the developed method, it is very promising as a rapid bioassay method for supporting the medical response to an emergency where internal contamination of (90)Sr is involved.

Field deployable technique for 90Sr emergency bioassay

Rapid bioassay is very important for immediate and near-term consequence management, which includes identifying contaminated individuals and providing necessary medical intervention during a radiological or nuclear emergency. This paper reports the application of a newly developed bioassay technique for (90)Sr in urine on a field deployable instrument, the Triathler. Performance of this field technique for sensitivity, accuracy and repeatability is evaluated against bioassay criteria (ANSI N13.30). This field technique offers the following analytical merits: (1) minimum detectable activity of 121 Bq l(-1) when 20 ml of urine is used; (2) relative bias of 11.1 % and relative precision of 3.2 % at the level of 45 Bq per 20 ml of urine and (3) sample turnaround time of less than 1 h. The technique meets the requirements for emergency bioassay when a committed effective dose of 0.5 Sv is used as the action dose threshold for medical intervention. Sample throughput can be significantly improved if this technique is automated.

Method comparison for 241Am emergency urine bioassay

241Am is one of the high-risk radionuclides that might be used in a terrorist attack. 241Am in urine bioassay can identify the contaminated individuals who need immediate medical intervention and decontamination. This paper compares three methods for the measurement of 241Am in urine, namely liquid scintillation counting (LSC), inductively coupled plasma mass spectrometry (ICP-MS) and gamma spectrometry (GS), at two levels, 20 and 2 Bq l(-1). All three methods satisfied the ANSI N13.30 radio-bioassay criteria for accuracy and repeatability. ICP-MS offered the best sensitivity and fastest sample turnaround; however, the ICP-MS system used in this work may not be available in many bioassay laboratories. LSC and GS are more commonly available instruments. GS requires minimal or no sample preparation, which makes it a good candidate method. Moreover, the sample throughput can be significantly improved if the GS and LSC methods are automated.

Fast methods for 239Pu faecal bioassay

For timely monitoring of internally contaminated individuals following radiological or nuclear emergency events, two fast bioassay methods were developed for the measurement of 239Pu in faecal samples, one for a sample representing 24-hour excretion and the other for a sample representing 10% of 24-hour excretion. Samples were decomposed either by ashing/microwave digestion or by acid refluxing. They were measured by ICP-MS following solid phase extraction using TEVA resin from Eichrom®. The two methods were assessed against performance criteria for radionuclide bioassay defined by ANSI N13.30 for their accuracy and repeatability. Both methods satisfy the requirements and are sensitive enough for emergency population screening. The method for small samples has a much shorter sample turnaround time, making its application more promising.

A study on the levels of radioactivity in fish samples from the experimental lakes area in Ontario, Canada.

To better understand background radiation levels in country foods, a total of 125 fish samples were collected from three lakes (Lake 226, Lake 302 and Lake 305) in the Experimental Lakes Area (ELA) in Ontario of Canada during the summer of 2014. Concentrations of naturally occurring radionuclides ((226)Ra, (210)Pb and (210)Po) as well as anthropogenic radionuclides ((134)Cs and (137)Cs) were measured. This study confirmed that (210)Po is the dominant contributor to radiation doses resulting from fish consumption. While concentrations of (210)Pb and (226)Ra were below conventional detection limits, (210)Po was measured in almost all fish samples collected from the ELA. The average concentration was about 1.5 Bq/kg fresh weight (fw). None of the fish samples analysed in this study contained any detectable levels of (134)Cs. An average (137)Cs level of 6.1 Bq/kg fw was observed in freshwater fishes harvested in the ELA, almost twice that of samples measured in the National Capital Region of Canada in 2014 and more than 20 times higher than the levels observed in marine fish harvested from the Canadian west coast in 2013 and 2014. However, it is important to note that the concentrations of (137)Cs in fish samples from these inland lakes are considered very low from a radiological protection perspective. The resulting radiation dose for people from fish consumption would be a very small fraction of the annual dose from exposure to natural background radiation in Canada. The results indicate that fishes from inland lakes do not pose a radiological health concern.

EURADOS intercomparison on emergency radiobioassay

Nine laboratories participated in an intercomparison exercise organised by the European Radiation Dosimetry Group (EURADOS) for emergency radiobioassay involving four high-risk radionuclides ((239)Pu, (241)Am, (90)Sr and (226)Ra). Diverse methods of analysis were used by the participating laboratories for the in vitro determination of each of the four radionuclides in urine samples. Almost all the methods used are sensitive enough to meet the requirements for emergency radiobioassay derived for this project in reference to the Clinical Decision Guide introduced by the NCRP. Results from most of the methods meet the requirements of ISO 28218 on accuracy in terms of relative bias and relative precision. However, some technical gaps have been identified. For example, some laboratories do not have the ability to assay samples containing (226)Ra, and sample turnaround time would be expected to be much shorter than that reported by many laboratories, as timely results for internal contamination and early decisions on medical intervention are highly desired. Participating laboratories are expected to learn from each other on the methods used to improve the interoperability among these laboratories.

An emergency radiobioassay method for 226Ra in human urine samples

A new radioanalytical method was developed for rapid determination of (226)Ra in human urine samples. The method is based on organic removal and decolourisation of a urine sample by a polymeric (acrylic ester) solid phase sorbent material followed by extraction and preconcentration of (226)Ra in an organic solvent using a dispersive liquid-liquid microextraction technique. Radiometric measurement of (226)Ra was carried out using a liquid scintillation counting instrument. The minimum detectable activity for the method (0.15 Bq l(-1)) is lower than the required sensitivity of 0.2 Bq l(-1) for (226)Ra in human urine samples as defined in the requirements for radiation emergency bioassay techniques for the public and first responders based on the dose threshold for possible medical attention recommended by the International Commission on Radiological Protection (ICRP). The accuracy (expressed as relative bias, B(r)) and repeatability of the method (expressed as relative precision, S(B)) evaluated at the reference level (2 Bq l(-1)) were found to be -4.5 and 2.6 %, respectively. The sample turnaround time was <5 h for a single urine sample and <20 h for a batch of six urine samples. With the fast sample turnaround time combined with the potential to carry out the analysis in a field deployable mobile laboratory, the newly developed method can be used for emergency radiobioassay of (226)Ra in human urine samples following a radiological or nuclear accident.

International workshop on emergency radiobioassay: considerations, gaps and recommendations.

An international workshop on emergency radiobioassay was held in Ottawa, Canada, 1-3 September 2010. Sixty-five scientists and public health officials from five countries attended the workshop and gave 36 presentations. During the workshop, many considerations were raised, gaps identified, and recommendations given for emergency radiobioassay for both preparedness and response in case of a radiological or nuclear incident. In short, some bioassay methods and protocols need to be developed, validated, and exercised; national and international radiobioassay laboratory networks should be established; and communications and collaborations among public health officials, monitoring experts, and medical staff are encouraged. All these activities are required to make us better prepared for an RN emergency.

Preliminary studies of an 18-crown-6 ether modified magnetic cation exchange polymer in rapid 90Sr bioassay

A cation exchange polymer resin embedded with magnetic nanoparticles and modified with crown ether was developed for urinalysis to rapidly monitor levels of 90Sr exposure in humans who have been involved in a nuclear event. Invention of the resin matrix of 2-acrylamido-2-methyl-1-propanesulfonic acid cross-linked with divinylbenzene incorporated a Sr2+ chelating agent, di-tert-butyl-cyclohexano-18-crown-6 through surface immobilization using a molecular modifier 1-octanol. The performance of these magnetic cation exchange resin particles was investigated by separating 90Sr in the presence of 90Y progeny. Masking agents and precipitants were examined to ascertain that sodium hydroxide at pH 7.5 was capable of selectively removing 89 ± 2% 90Y before subsequent 90Sr uptake. Preliminary investigations in rapid urinalysis were successful in isolating 83 ± 2% 90Sr when pH was optimized to 9, with a sample turnover time <2 h, which is promising for radiological emergencies.

Metabolism of 210Po in rats: volatile 210Po in excreta

Polonium-210 ((210)Po) is one of the most toxic radionuclides and was used as a poison in the Alexander Litvinenko case. In this study of the metabolism of (210)Po in rats, volatile (210)Po in excreta was measured, filling a knowledge gap of the previous studies. Five rats were intravenously administrated with 2 kBq and another five with 10 kBq of (210)Po (citrate form). They were housed in a glass Metabowl system for 4 d following the administration. Volatile (210)Po from the excreta was collected in a trapping system filled with liquid scintillation cocktail and was measured by liquid scintillation counting. Results showed that the daily excretion of volatile (210)Po by the rats is in a very small percentage (0.002-0.009 %) of the administered amounts. However, if the administered amount is large, the excretion of volatile (210)Po can be significant.