The combined eluant1 9MHC s containing americiu curiud man m are evaporated to dryness and the residue is dissolved into 20 ml 8M HNO_. The pH of the solution is then adjusted to 2.5 with ammonia and the solution is transferred to a 250 ml separatory funnel. Twenty five ml of HDEHP solution is added and Am is extracted to the organic phase by shaking vigorousl organiraine 2 Th r . yfo c phas washes ei d twic e0.075l witm 5 1 2 hMHC to remove extracted lanthanides and the aqueous phase is discarded. Americium is then back-extracted twice with 25 ml 12 M HC1 each time for 2 min. The aqueous phase combinee sar d evaporatedan concenf o l drynessm o t d-w fe A . trated HC1 are added to the residue and evaporated to dryness. This treatment is repeated several times. The Am thus separated is further purified by anion as well as cation exchange procedures from impurities, such as traces of Fe, Pu, U, Po and Th. This is done by passing the 9M HCl solution of the residue through a small column (<j» 5mm x 150 mm) containing floa Dowe f t o wml/inn5 a l rat0. x1 m f wel3 s Dowef eo . a o s la 0 l x5 m 2 The Am passes through the column while remaining traces of Fe, Pu, U and Po are sorbed on Dowex 1 and that of Th on Dowex 50. Although lanthanides in this medium eventually pass through the column, the speed of the passage is very much slower than that of Am. This difference in the speed of passage makes it possible to eliminate lanthanides from the Am fraction by limiting the volum washingf eo colume Th . washe s ni d wit columh2 n volumf eo HClM 9 . e electro-depositioTh purifiee th f no d plutoniud man americium fractions were performed by the procedure described by Talvitie . The effluent and washings from the plutonium separation were evaporated to drynes concentratef re-dissolved o san l m 6 0. n di d H-SO, americiue ;th m fractio evaporates nwa dryneso t d reconstituted san concentratef do witl m h1 d H-SO,. After heating to fumes of SO , 2 ml of H.O, 50 ml of 1M oxalic acid and 1 drop of 1 M DTPA (ammonium diethylamine-triamine penta acetic acid) is solutione addeth o t d . Several drop 0.02f so % thymol blue indicatos i r the adjustes additioy i b n H 5 p indicaton adde a *o 2. e t df s n o th a d d ran ammonium hydroxide. 4.2 Determinatio americiuf no curiud man m using ion-exchange nitric-acid-methanoe inth l mediu environmentar mfo l analysis E. Holm and R. Fukai While transplutonic element onle sar y slightly sorbe anioo t d n exchangers from hydrochloric or nitric acid media, the presence of alcohol enhances the anionic exchange of these elements, especially in nitric and 86 sulfuric solutions. Haidvogel et a.1, showed this enhancement by thin- 78 layer chromatography sorptioe th ; f transplutonino c elements increased with increasing alcohol bindine contenth d gtan wit ion-exchangee hth s rwa stronge nitrie th n cri medium tha sulfurie n th tha n i t c medium. Guseva 87,88 et al. separated americium from curium, both at relatively high levels, nitrie inth c acid-methanol mixture, observing thagreatee th t atomie th r c number, the stronger the sorption. In the present work a method has been developed for determining americium and curium in environmental samples, on the basis of the difference between the sorption characteristics to anion exchangers in the acid-methanol system of these transplutonic elements and those of plutonium, polonium and thorium. The method also permits us to perform sequential determinatio plutoniumf no , when necessary radiochemicae Th . l separatio americiuf no m from generallcuriut no s i m y required since modern 241 a-spectrometry resolve majoe sth rm (5.4 A a-pea9 f kMeVo ) from either 242 246 that of Cm (6.10 MeV) or Cm (5.80 MeV), which possibly co-exist with Am in environmental samples. The reagent separatioe s th use followss n a i d e nar : Nitric acid-methanol mixtures: 1M HNO -90% CH OH solution and 0,5M HN03-70% CH3OH solution. 1st anion exchange resin column: Dowe (X8x1 , 100-200 mesh) <f> 1cm, volum. ml 0 e1 2nd anion exchange resin column: Dowex 1 (X2, 50-100 mesh) <f> 1cm, volum. ml 0 e2 Cation exchange resin column: Dowex 50 (X8, 200-400 mesh) <j> 1cm, volume 5 ml. 241 Americium-243 solution: chemical yieldm A monito r rfo (5 dpm/m )O 1.n MHN li Plutonium-23 plutonium-24r 6o 2 solution: Chemical yield monitor 21J 8 91JyQ 9&u0 for °Pu and ^ '^ pu (5 dpn/ml in 1M HN03), Biologica sedimenr lo t sample driee sar 105-110°Ct a d , weighed and place porcelaia n i d n crucibl whico et yiele hth d determinantsw fe ,a f\ t n ty t\ £ /j r /) normalle ar , Pu y added r o u ,P Afte d ran dryindpm A m eacg f ho again samplee ,th ashee sar 500°t a d C overnight h obtaineas e leaches Th i d. d wit mixturha a mixturconcentratef eo e of wit1 additiow concente dHC fe th h HNO d a an _f rno milliliters of H (30%). 3+ Water samples are acidified, to which iron carrier (50mg Fe ) is added. The actinides are co-precipitated with Fe hydroxide by adding ammonia precipitate Th . centrifuges ei dissolved an d 9-1n i d 2 M HC1. After 79 the addition of a few drops of H~0 (30%), the solution is heated and kept at 80°C for 20 min. The acidity of the solution is finally adjusted to 9M HC1. After cooling, the solution is passed through the first colum theDowed f no an n x 1 throug Dowee hth column0 x5 , whic directls hi y connected with the first column, at a flow rate of 2ml per min. Iron (III) is sorbed to the Dowex 1 column with plutonium (IV) as well as uranium and polonium. Thoriu Dowee sorbes mi th column 0 x5 o t d . Trivalent actinides, americium and curium, on the other hand, pass through both columns. The column washee sar d with 50ml 9M HC1 effluene th , washingd tan combinee sar d and evaporate drynesso t d residue Th . thes ei n dissolve 1n Mi d HNO,-90% solutioCH HO n (50-100 ml). In order to obtain further purification of americium and curium, the solutio passes ni d throug secone th h d Dowe columx1 floa t wna rate minr pe .l oAmericiu2m f d curiu man colume e sorbeth mar n no d with other impurities, suc remainins ha g plutonium, poloniu d thoriumman colume Th .n is washed with HN0 M 1 60mCH.OH % f -l90 trivaleno e Th . t actinidee sar 0 *— J j then eluted with 0.5M HNO.-70% CH-OH (70 ml). When the plutonium determination is required, plutonium can be eluted from the first Dowex 1 column with 1.2M HC1 after washing with ~ 85 7.2M HNO, and analyzed by the procedure described by Talvitie . The elute which contains americium and curium is evaporated to dryness and the residue is dissolved with 0.8 ml concentrated HLSO,. The solution is diluted with distilled water and partially neutralized with finaa ammonid lan volum2 givo electrodepositioe t aH Th ep e. abouml 0 1 t n of americiu curiud man m from this solution ont stainlesoa s steel diss i c performe electrin a t a d c curren 1.2f hour1 to r Ausiny ,fo b disposablga e polyethylene electrolysi n viaa s la s cell similaA . r procedure th r efo 71 electrodepositio plutoniuf no alreads mha y been described presene th n I t work a-spectrometre ,th americiur yfo d an m curium was carried out using a silicon surface barrier detector having a 2 sensitive areresolutioe 300mf Th ao a-spectr e . mth f no 35-4s awa V 0ke 241 peam A k (5.4e th 9r MeV fo fule termn th i )l f widtso halt ha f maximum. The minimum detectable activity was 0.01 pCi for a 1000-min counting time. The key to precise determinations of americium in environmental samples is to obtain good decontamination from naturally-occurring 8 22 a-emitters, such as 21DP o (a-energy, 5.30 MeV) and Th (5.42 MeV) as 238 well as from the artificial fallout radionuclides such as Pu (5.49 MeV). 241 Their a-energies would interfere with the a-spectrometry of Am (5.49 MeV) 243 or of the yield-determinant Am (5.28 MeV). For curium determinations 80 O OC « , O Q£ separation from , Pu (5.76 MeV) is essential when Pu has been used as the yield monitors for plutonium, as its a-peak overlaps with that of 744 Cm (5.80 MeV). The decontamination of polonium with the present procedure verifies wa analyziny b d g samples which were know contaio nt n relatively 210 hig withou, hPo levelt f addinso y yielgan d monitor decontaminatioe Th . n factor for Po is estimated to be in the order of 10 . 210 However, since it was also observed that Pb is strongly sorbed on the anion exchange resin from the nitric acid-methanol medium, it 210 is possible that a small fraction of the Pb may be carried over to the 243 americium fraction and interfere with the a-spectrometry of Am, when 210 the content of Pb in samples in question is exceptionally high.