Nucfilm Discs Brochure

PRODUCT SHEET 04/05/2010 Nucfilm Discs Ra-NucfilmDiscs Main Applications - Determination of alpha emitting Ra isotopes in water samples via alpha spectrometry - Determination of Ra-228 via Th-228 ingrowth and alpha spectrometry Packing Order N°. Form NU-D20-RA Box of 20 Ra-NucfilmDiscs NU-D100-RA Box of 100 Ra-NucfilmDiscs Physical and chemical properties Disc diameter : 24.5 mm Active diameter: 24 mm, Disc thickness : 1.6 mm Single absorbing side, back side writeable Option : Disc diameter : 26.5 mm Active diameter: 26 mm, Disc thickness : 1.6 mm Single absorbing side, back side writeable Support : Polyamid66 Active component: MnO2 Conditions of utilization Recommended T of utilization : / Recommended pH of utilization : 4 - 8 Storage : Dry and dark For additional information see enclosed literature study Methods1Reference Description Matrix Analytes Support app_note_ra_disc Nucfilm application note: “How to use Ra-NucfilmDiscs” water Ra-226, Ra-224 Ra-228 Disc 1 Discs and methods developped by Nucfilm GmbH. PRODUCT SHEET 04/05/2010 Nucfilm Discs U-NucfilmDiscs Main Applications - Determination of U isotopes in water samples via alpha spectrometry Packing Order N°. Form NU-D20-U Box of 20 U-NucfilmDiscs NU-D100-U Box of 100 U-NucfilmDiscs Physical and chemical properties Disc diameter : 24.5 mm Active diameter: 24 mm Disc thickness : 1.1 mm Single absorbing side, back side writeable Support : Polycarbonate Active component: Diphonix® resin Conditions of utilization Recommended T of utilization : / Recommended pH of utilization : 2 - 3 Storage : Dry and dark For additional information see enclosed literature study Methods2Reference Description Matrix Analytes Support app_note_u_disc Nucfilm application note: “How to use U-NucfilmDiscs” water U-234/235/238 Disc 2 Discs and methods developped by NucFilm GmbH. LITERATURE STUDY 3 Nucfilm Discs Radium adsorbing discs (Ra- NucfilmDisc) MnO2 is renowned for efficiently adsorbing Ra even at high Ca concentration. Recent improvements in the fabrication of MnO2 layers based on anterior works (1-5) now allow the fabrication of selectively adsorbing MnO2 coated as a thin film onto the surface of a polyamide disc. These coated substrates are available as Ra -NucfilmDiscs. Due to their high selectivity for Ra the discs allow the direct determination of Ra isotopes in water samples without applying additional radiochemical separation methods. The discs are contacted with the untreated water samples (pH 4 – 8, typical volume = 100 mL) under stirring for 6h. Under these conditions the Ra extraction is typically greater 90%. The dried disc can then be measured with a solid state alpha detector. The energy resolution of the obtained sources is very good as demonstrated in Fig.1. Using a 900 mm2 detector and a detector to sample distance of 10 mm the 4780 keV Ra-226 peak can be fitted with the sum of a gaussian and an exponential tailing of gaussian: FWHM 30 to 40 keV and tailing: 20 to 30 keV to 1/2 peak maximum. The analysis of a 100 mL sample (counting time t = 80000 s, 900 mm2 Si-detector at 10 mm distance) typically results in a detection limit (LLD) of 5 mBq.L-1 for 226Ra. Fig. 1 : Alpha spectrum of a radium adsorbing thin film exposed to a Portuguese mineral water. The above mentioned yield of > 90% was established for water samples having drinking water quality. With some precaution other water samples can be analyzed too, but one has to take into account that the adsorption efficiency may depend on the chemical composition of the sample. MnO2 has a high selectivity not only for Ra but also for Ba, that when present at mg.L-1 levels, competes with Ra for the adsorption sites, resulting in lower yields. If there are any doubts the absorption efficiency can be determined by subsequently exposing two discs to the same sample (template exposition). Each disc will adsorb the same fraction of Ra still present in solution, it is thus possible to calculate the activity of the Ra isotopes in the sample based on the count rates of each of the discs. For low sample activities (in the order of tens of mBq.L-1) the count rates are too low to use this method, in this case a known Ra-226 activity (some 10 mBq) can be added to the sample before exposing the second disc. It is essential to use a Ra-226 standard solution with a low Ba content (final Ba concentration in the sample to be analyzed << mg.L-1). In the case of sparkling waters with high mineral content Na2EDTA is added to complex calcium. This prevents precipitation of Ca due to loss of CO2. No noticable effect of this complexation on Ra adsorption efficiency (up to 1g/l Na2EDTA added) is observed. Apart from Ra, Po is also adsorbed with high efficiency. Uranium adsorption is in general low, less than 5% of the U-238 or U-234 activities present in the sample are adsorbed. There are large variations in this adsorption efficiency, these variations may be due to differences in the chemical form in which uranium is present in the sample; CO32- forms quite stable anionic or neutral complexes with the uranyl cation (UO22+), which are not adsorbed by the MnO2. Carbonate thus helps avoiding U adsorption; the same is true for Th (6). The Ra-NucFilm discs can also be used for the determination of Ra-228 by following the ingrowth of Th-228 over an extended period (7). Uranium adsorbing discs (U-NucfilmDisc) U-Nucfilm discs are based on finely ground Diphonix resin® (8, 9) that has been immobilized on a polycarbonate disc in the form of a thin layer (Uranium is adsorbed very close to the surface, within about 1 µm.). The Diphonix resin® is a very strong cation exchange resin containing diphosphonate groups, which determine the resins selectivity for actinides, and sulfonate groups for increased absorption kinetics. It showed to have the required selectivity for U, LITERATURE STUDY 4 while Ra adsorption is very low (8, 9). Additionally it allows working at low pH and thus eliminating potential interference of the U extraction by its complexation by dissolved CO32. U adsorption is considerably slower on these films than the Ra adsorption on MnO2 films; it takes about 20h until equilibrium is reached (4h to 50% equilibrium). After 20h a 24 mm diam. disc exposed to an acidified, stirred 100 mL sample takes up typically more than 90% of the U. The pH can be adjusted with a wide range of different acids (e.g. formic, citric or nitric acid) and should be kept below pH 3, preferably at pH 2. It is recommended to use formic acid. After drying the exposed disc can be measured with a solid state alpha detector. As shown in Fig.2 energy resolution is not quite as good as for the MnO2 films. Using a 900 mm2 detector and a detector to sample distance of 10 mm the uranium peaks can be fitted with the sum of a gaussian and an exponential tailing of gaussian: FWHM 30 to 40 keV and tailing: 30 to 50 keV to 1/2 peak maximum, nevertheless the U-234 and U-238 peaks are clearly separated. The analysis of a 100 mL sample (counting time t = 80000 s, 900 mm2 Si-detector at 10 mm distance) typically results in a detection limit (LLD) of about 10 mBq.L-1 for U-234 and U-238. Fig 2: Alpha spectrum of a mineral water sample („Aproz Ancienne“, Valais, Switzerland) obtained using a U-Nucfilm disc; Counting conditions: 900 mm2 Si-detector at a distance of approx. 11 mm, acquisition time : 80‘000 s. Added tracer activity is 200 mBq.L-1. Literature (1) Glöbel, B. and Berlich, J., Eine einfache und schnelle Methode zur Bestimmung von 226Ra in wässrigen Proben, In: Proc. Fachgespräch Ueberwachung der Umweltradioaktivität, 22-24 March 1983, Karlsruhe, 1983 (2) Moore, W.S. and Reid, D.F., Extraction of Radium from Natural Waters Using Manganese Impregnated Acrylic Fibers, J. Geophys. Res. 78, 8880-8886, 1973 (3) Surbeck H., Piller, G. and Ferreri, G., Die Suche nach Radonquellen, In: Tagungsbericht "Radon und die Strahlungsbelastung der Lunge", Crameri, R. and Burkart, W.(Eds.), PSI-Bericht Nr.22, Villigen, Switzerland, 1989. (4) Surbeck, H., Determination of natural radionuclides in drinking water, a tentative protocol, Sci.Total Environment, 173/174, 91-99, 1995. (5) Moon D.S., Burnett W.C., Nour S., Horwitz E.P., Bond A., Preconcentration of Radium Isotopes from Natural Waters Using MnO2 resin, Applied Radiation and Isotopes, 59, 255 – 262, 2003 (6) Morvan K., Andres Y., Mokili B. and Abbe J.C., Determination of Radium-226 in Aqueous Solutions by a-Spectrometry, Anal. Chem., 73 (17), 4218–4224, 2001 (7) Eikenberg, J., Tricca, A., Vezzu, G., Bajo, S., Ruethi, M. and Surbeck, H., Determination of Ra-228, Ra-226 and Ra-224 in natural water via adsorption on MnO2-coated discs, J. Environmental Radioactivity, 54, 109-131, 2001 (8) Horwitz, E.P., Chiarizia, R., Diamond, H. Gatrone, R.C., Alexandratos, S.D., Trochimzuk, A.Q. and Creek, D.W., Uptake of Metal Ions by a New Chelating Ion Exchange Resin, Solv. Extr. Ion Exch., 11, 943ff, 1993 (9) Diphonix® Resin: A Review of its properties and applications Chiarizia R. et al., Sep. Sci. Technol., 32, 1 – 35, 1997