Reassessment of 239Pu on planchets from human urine samples at ultra-trace levels using Aridus-ICP-SFMS and AMS

REASSESSMENT OF 239 PU ON PLANCHETS FROM HUMAN URINE SAMPLES AT ULTRA-TRACE LEVELS USING ARIDUS-ICP-SFMS AND AMS He ´c o He na ´ndez-Mendoza1, Elena Chamizo2,*, An onio Delgado1, Manuel Ga cı ´a-Leo ´n3 and Abel Ylle a1 1 Cen o de In es igaciones Ene ge ´ icas, Medioambien ales y Tecnolo ´gicas (CIEMAT), A . Complu ense 22, 28040 Mad id, Spain 2 Cen o Nacional de Acele ado es (CNA), A . Thomas Alba Edison, 41092 Se illa, Spain 3 Depa amen o de Fı ´sica A o ´mica, Molecula y Nuclea , Uni e sidad de Se illa, 41012 Se ille, Spain *Co esponding au ho : [email protected] Recei ed Oc obe 17 2011, e ised Ap il 11 2012, accep ed Ap il 25 2012 New analy ical me hods de eloped a he acili ies he e, based on wo ul a-sensi i e mass spec ome y (MS) echniques, in- duc i ely coupled plasma sec o ield mass spec ome e wi h a desol a o sys em (A idus-ICP-SFMS) and accele a o MS (AMS), ha e been applied in his wo k o he eassessmen o 239 Pu in alpha spec ome y (AS) planche s co esponding o spiked human u ine samples. The ob ained 239 Pu minimum de ec able ac i i ies (MDAs) alues by A idus-ICP-SFMS and AMS we e 3 g (∼6.92 mBq) and 0.4 g (∼0.92 mBq), espec i ely, pe sample, which a e much be e han hose a ainable by AS [50 g (∼115.3 mBq) o 239 Pu pe sample, app oxima ely]. The e o e, i is demons a ed ha he MS echniques employed in his wo k a e e y powe ul ools o in e nal dosime y s udies in human u ine samples, gi ing excellen esul s when he eassessmen o AS planche s is needed (samples wi h a Pu concen a ion below o a he MDA le els measu able by AS). This wo k is he con inua ion o an a icle published in J. Anal. A . Spec om. 25 (1410–1415) 2010. INTRODUCTION The success ul measu emen and assessmen o in- e nal exposu e o adioac i i y in dosime y s udies a e highly dependen on he ins umen al capabili ies o measu ing adionuclides in biological samples (u ine, eces, blood o o he sec e ions) (1,2) . No mally, du ing he Pu bioassay o human u ine samples, i is manda o y o p econcen a e and pu i y he Pu ac ion. In he case o mass spec om- e y (MS) echniques, i is usually impo an o p e en he p esence o 238 U in he sample, because i can in e e e wi h he signal o he majo Pu iso ope 39 Pu (T 1/2 ¼24 110 y), and also o a oid ma ix e ec s. Fo hese pu poses, ion-exchange o solid-phase ex ac ion ch oma og aphy is ex ensi ely used in wo ldwide labo a o ies (3–8) . Alpha spec ome y (AS) is he mos commonly used adioanaly ical echnique o he de e mina ion o Pu in ou ine bioassay s udies, due o i s simpli- ci y and low cos . Howe e , his me hod is e y ime-consuming and i canno esol e he 239 Pu and 240 Pu peaks because o hei e y simila ene gies (5.15 and 5.16 MeV). Analy ical esul s om AS a e he e o e exp essed as he sum o he 239 Pu and 240 Pu ac i i y concen a ion (i.e. 239þ240 Pu). Addi ionally, his echnique shows some sensi i i y sho comings when he in ol ed 239þ240 Pu ac i i y le els a e below 0.3 mBq pe sample (1.3 pg o 239 Pu pe sample), due o he noise associa ed wi h he de ec o and he poo s a is ics (9) . On he o he hand, se e al pa ame e s, such as coun ing e iciency, chemical yield, sample coun ing ime, ace ac i i y used and backg ound condi ion he p ecision and accu acy o he esul s o low-le el samples and, he e o e, he minimum de ec able ac i i y (MDA) o AS (10–12) . Because o i s excellen de ec ion sensi i i y, MS echniques a e use ul ools o measu ing 239 Pu a sub- g le els, and also 240 Pu/ 239 Pu a omic a ios, which would be impossible o measu e using con en- ional adioac i e decay coun ing echniques. Due o he equi emen s imposed by he In e na ional Commission on Radiological P o ec ion (ICRP), echniques capable o measu ing 239/240/241 Pu iso- opes a concen a ions o 1 gl 21 in u ine samples a e becoming manda o y (13,14) . Di e en MS echniques, such as induc i ely coupled plasma (ICP) MS (3–6) , The mal ionisa ion MS (TIMS) (15,16) and accele a o MS (AMS) (14,17,18) ,a e good candida es o he dosime ic con ol o he popu- la ion exposed o ionising adia ion, opening up he possibili y o iden i ying and quan i ying small amoun s o di e en adionuclides in a sample, and also o e ing iso opic composi ion una ainable by adioac i e coun ing echniques (19 –22) . ICP-MS is one o he mos sui able me hods o he analysis o ac inides a ul a ace le els, in pa - icula 239 Pu, due o i s high sensi i i y, good #The Au ho 2012. Published by Ox o d Uni e si y P ess. All igh s ese ed. Fo Pe missions, please email: jou nals.pe [email protected] Radia ion P o ec ion Dosime y (2012), Vol. 152, No. 4, pp. 296–303 doi:10.1093/ pd/ncs078 Ad ance Access publica ion 23 May 2012 accu acy and p ecision and gene ally simple sample p epa a ion p ocedu e e sus AS (3) . Howe e , he ac- cu a e de e mina ion o Pu iso opes by ICP-MS is hampe ed by bo h spec al and non-spec al in e e - ences. Fo he analysis o Pu, he mos common in e e ences a e 238 UH þ and 238 UH 2 þ , which in e - e e wi h he 239 Pu and 240 Pu iso opes, espec i ely, due o he p esence o U. To a oid hese p oblems, wo complemen a y solu ions a e usually applied: he p econcen a ion and pu i ica ion o he Pu ac- ion using ion-ch oma og aphy esins (4,5) , and/o he educ ion o u anium hyd ide o ma ion using special sample in oduc ion sys ems, such as mic o- nebulize s wi h desol a o sys em (6) . On he o he hand, AMS has ecen ly been demons a ed o be a compe i i e echnique o he p ecise and accu a e de e mina ion o Pu a sub- g le els in u ine bioassay samples. I ea u es a high sensi i i y wi h i ually no ma ix e ec s (high e- jec ion o molecula isoba ic in e e ences), allowing he iden i ica ion o abno mal ac i i ies o Pu wi h no special chemical equi emen s (7) . The aim o his s udy was o de elop and alida e an analy ical me hod o he eassessmen o 239 Pu in AS planche s con aining small amoun s o 239 Pu ( om 8 o 40 g pe sample), using he A idus deso- l a o coupled wi h an ICP-SFMS, and a 1-MV compac AMS sys em. This is specially in e es ing o he au ho s’ esea ch cen e, CIEMAT (Resea ch Cen e o En i onmen and Ene gy and Technology), whe e he e is a big s ock o Pu elec odeposi s om human u ine samples om he popula ion o Paloma es (Alme ia, Spain), a ec ed by a nuclea ac- ciden in 1966, and om p o essionally exposed people. MATERIALS AND REAGENTS Ins umen a ion Spec opho ome y and AS C ea inine de e mina ion was ca ied ou by using a spec opho ome e Zuzi, Model 4211/20 (Auxilab S.L., Spain). AS measu emen s we e pe o med wi h an Alpha Analys In eg a ed Alpha Spec ome e (Canbe a, TECNASA S.L., Spain) equipped wi h Passi a ed Implan ed Plana Silicon de ec o s. These de ec o s ha e an ac i e a ea o 450 mm 2 and hei nominal alpha-peak ene gy esolu ion, exp essed as ull-wid h a hal -maximum, is 18 keV. The plan- che s (Pu sou ces) we e placed a 1.5 mm om he de ec o su ace. Fo he e alua ion o he da a, he Genie 2000 .2.2 so wa e (Canbe a) was used. HR-ICP-MS ins umen a ion Pu quan i ica ion was ca ied ou wi h an Elemen XR Mass Spec ome e (The mo Fishe Scien i ic, B emen, Ge many). The sample in oduc ion sys em employed was an A idus desol a o (CETAC Technologies, Inc., USA) wi h a Mic o low nebulize PFA-100 (Elemen al Scien i ic Inc., USA). Aqueous samples we e in oduced o he desol a o in he con inuous low mode by using an au o sample CETAC ASX-520 (CETAC Technologies, Inc., USA). The ICP o ch was shielded wi h a g ounded pla inum elec ode (Gua dElec odeTM, The mo Scien i ic, Ge many). Accele a o MS The measu emen s o 239 Pu we e pe o med using he 1-MV compac AMS sys em se up a he Cen o Nacional de Acele ado es (CNA, Se ille, Spain). The sys em was designed and manu ac u ed by High Vol age Enginee ing Eu opa (HVEE, Ame s oo , Holland). Ma e ials and eagen s 239 Pu and 242 Pu s anda ds we e ob ained om Na ional Physical Labo a o y (NPL, UK). S anda ds we e dilu ed wi h 2 M HNO 3 o ob ain s ock solu ions wi h a concen a ion o 20.3 mBq ml 21 (140.4 ng l 21 )o 242 Pu and 7.9 mBq ml 21 (3.4 ng l 21 )o 239 Pu. 237 Np (chosen as ex e nal s anda d o ICP-SFMS measu emen s) was ob ained om Ame sham In e na ional plc (UK). This s anda d was dilu ed wi h 0.1 M HCl o ob ain a s ock solu- ion wi h a concen a ion o 3.256 mBq ml 21 (123 ng l 21 ). Fo ICP-SFMS mass calib a ion, a ce i ied mul i-elemen solu ion XXIII (Ba, B, Co, Fe, Ga, In, K, Li, Lu, Na, Rh, Sc, Y, Tl and U) om Me ck (Ge many) was used. The es o he sal s and solu- ions we e p epa ed using analy ical g ade eagen s om Me ck. High-pu i y wa e (.18 MVcm 21 ) was ob ained om a Milli-Q Elemen A10 Cen u y (Millipo e Ibe ´ ica, Spain). Ni ic acid was pu i ied by sub-boiling dis illa ion (Duopu , Miles one S. .l., I aly). Ce i ied A gas (99.999 %) was supplied by Ai Liquide (Spain). Ce ipu w i on ICP s anda d (Me ck, Ge many) and 500-mesh pu e aluminium powde (Al a-Aesa , UK) we e employed o p epa - a ion o he AMS ca hodes. AG1X2 anion-exchange ch oma og aphy esins (Bio-Rad Labo a o ies S.A., Spain) we e used o Pu pu i ica ion. The ICP- SFMS measu emen s we e ca ied ou in a clean oom (ISO 6 class) a 24+18C. Expe imen al The di e en ea u es o he me hod o he ex ac- ion and pu i ica ion o 239 Pu in human u ine samples and he eassessmen o AS planche s o ICP-SFMS and AMS de e mina ions a e shown in he diag am in Figu e 1. REASSESSMENT OF 239 PU BY ARIDUS-ICP-SFMS AND AMS 297 Figu e 1. Schema ic diag am o he p epa a ion p ocedu e o u ine samples and measu emen s o Pu by AS, A idus-ICP- SFMS and AMS: (1) collec ion o sample ( ime: 24 h); (2) co-p ecipi a ion (24 h); (3) Mine alisa ion (2 h); (4) adiochemis y (3 h); (5) elec odeposi ion (2 h); (6) eco e y o Pu om planche s (24 h) and (7) p epa a ion o he ca hodes o AMS (3 h) and eassessmen o 239 Pu by A idus-ICP-SFMS and AMS. This igu e appea s in colou in he online e sion o Radia ion P o ec ion Dosime y. H. HERNA ´NDEZ-MENDOZA ET AL. 298 C ea inine measu emen s Measu emen s o c ea inine concen a ions in u ine ha e been commonly used in he labo a o y o es i- ma e 24 h exc e ion o adionuclides om u ine samples collec ed in a day, hen 14 samples o 24 h human u ine (V sample ¼1725+114 ml) we e collec ed om se e al heal hy adul male olun ee s. The ana- ly ical p ocedu e was ini ia ed he same day o he collec ion by he de e mina ion o c ea inine con en in he u ine samples, in o de o check whe he hose me he equi emen s needed p e ious o bio- assay. The me hod is based on he Ja e ´ eac ion: addi ion o sodium pic a e in o he u ine and o - ma ion o a ed-coluo ed complex (sodium pic ama e) (23) . The colou in ensi y is di ec ly p o- po ional o he concen a ion o c ea inine a a spe- ci ic wa eleng h (520 nm), which is measu ed wi h a spec opho ome e (24) . Co-p ecipi a ion The me hod ca ied ou o co-p ecipi a ion is desc ibed in Kuwaba a and Noguchi (8) and Rob edo e al. (9) The 24 h u ine samples we e ans e ed in o espec i e g adua ed cylinde s, acidi ied wi h concen- a ed HNO 3 o pH¼1, and hea ed in a ho pla e wi h magne ic s i ing a 808C du ing 2 h. Then, he ho samples we e spiked wi h known amoun s o 242 Pu (8.4 pg) as in e nal s anda d, and 239 Pu ( om 8 o 40 g, see Table 1). Nex , 1 ml o concen a ed o hophospho ic acid was added, con inuing he hea ing and he s i ing o a u he 1 h. Then, he Pu was co-p ecipi a ed by he addi ion o concen- a ed ammonium hyd oxide un il pH¼9, keeping he same condi ions o 1 h. The p ecipi a e was allowed o se le o e nigh and hen sepa a ed by decan ing and cen i uga ion. The supe na an was disca ded, and he g adua ed cylinde was washed se e al imes wi h 0.5 M HNO 3 . The washings we e also ans e ed in o he cen i uge ube, and he p e- cipi a e was dissol ed wi h 5 ml 21 o 8 M HNO 3 plus slow addi ion 3 ml o concen a ed H 2 O 2 . The p ocedu al blanks (unspiked u ine samples) we e p ocessed in he same way. Mine alisa ion, adiochemis y, elec odeposi ion and p epa a ion o he ca hodes o AMS A summa y o he p ocesses in ol ed in his sec ion is gi en in Figu e 1. A de ailed desc ip ion has been p o ided in p e ious s udies (25) . Reco e y o Pu o planche s eassessmen In o de o de e mine he adiochemical yield du ing Pu pu i ica ion, he samples we e p e iously mea- su ed by AS. A e ha , he ex ac ion o he elec odeposi s was ca ied ou by dipping he plan- che s in o 20 ml o 5 % HNO 3 o e nigh . Nex , he planche s we e insed wi h 5 % HNO 3 and he esul ing solu ions we e hea ed o d yness, dilu ed o 10 ml o he same acid in olume ic lasks, and di ided in wo win aliquo s o he A idus-ICP- SFMS and he AMS de e mina ions. In he case o he ICP-SFMS aliquo s, 4.4 g o 237 Np we e also added as an ex e nal s anda d. RESULTS AND DISCUSSION C ea inine es The Pu is a long-li ed adionuclide ha is exc e ed om he human body in e y small amoun s, which canno always be easily de ec ed by AS. The ecom- menda ions o good ou ine analysis o Pu in u ine es ablish ha he sample mus con ain he c ea inine equi alen o , a leas , o 24 h exc e ion (26) . This con ibu es o minimise he unce ain y o he esul s no malised o 24 h exc e ion, specially when analys- ing spo u ine samples (7,13,27) . The e o e, he de e - mina ion o c ea inine in u ine is essen ial o moni o ing he exc e ion o long-li ed adionuclides and i is also a decisi e es o accep ing o ejec ing he sample (28) . In his wo k, he a e age c ea inine concen a ion was 1.1+0.13 g l 21 (n¼15), which is in ag eemen wi h he ICRP-89 ecommenda ions o accep ing u ine samples o dosime y s udies (10) . T ea men o sample and pu i ica ion o Pu The co-p ecipi a ion o Pu wi h calcium phospha e in ammonia medium was pe o med o p e-concen- a e i , because i is adequa e o pe o m in human u ine a a sub-pg/l concen a ion le el o Pu. No mally, he ou ine bioassay o long-li ed adio- nuclides equi es mine alisa ion o he sample, which is usually ca ied ou by we ashing o he p ecipi a e ollowed by mu le u nace incine a ion (9) . This p ocess is e y ime-consuming and edious. The e o e, in his wo k, he mine alisa ion was pe - o med by mic owa e-assis ed acidic diges ion (8 M HNO 3 and concen a ed H 2 O 2 ) o he calcium phos- pha e p ecipi a e, which accele a es he p epa a ion o he sample. When using MS and adiochemis y echniques o Pu quan i ica ion in low-le el samples, he elim- ina ion o ma ix elemen s con ained in he sample is a mus . In his wo k, his was achie ed using anion-exchange esins (BioRad AG1X2). The pu i i- ca ion o Pu using AG1X2 esin does no p esen signi ican d awbacks in con as o o he Pu pu i i- ca ion p ocesses which, in p inciple, a e as e (5) .In case, he necessa y ime o p ocessing 10 samples was 2–4 h. Mo eo e , as measu ed by AS, AG1X2 REASSESSMENT OF 239 PU BY ARIDUS-ICP-SFMS AND AMS 299 esin o e s an excellen chemical eco e y o he Pu ac ion in u ine samples (Table 1). Op imisa ion o A idus-ICP-SFMS pa ame e s The ins umen al se ings we e op imised o he quan i ica ion o 237 Np 239 Pu and 242 Pu. Op imisa ion was pe o med in h ee s eps: (1) Tuning he pa ame e s o A idus (a gon and ni- ogen low) o ob ain he maximum in ensi ies o 115 In and 238 U iso opes, using a dilu ion (1:10) o he ce i ied mul ielemen solu ion in low esolu ion mode. The signal in ensi y o hese iso opes was abou 7.010 5 cps and 1.010 6 cps, espec i ely, and he 238 U oxides con en in he plasma was 0.6 %. (2) Op imisa ion o maximum ion in ensi y o 242 Pu and minimum backg ound a m/z¼239 using a 242 Pu s anda d solu ion o 0.4 pg l 21 . The backg ound signal ob ained du ing his s ep was 0.3+0.1 cps o m/z¼239. Addi ionally, a s abili y es was also pe o med o moni o ing he signal o 237 Np, 238 U, 239 Pu, 240 Pu and 242 Pu iso opes (10, 0.1, 32, 2.7 and 42 pg l 21 , espec - i ely) in s anda d samples o hese iso opes du ing 15 min. (3) Op imisa ion o he me hod o he measu e- men o 237 Np, 238 U, 239 Pu, 240 Pu and 242 Pu iso- opes. Ins umen al ope a ion condi ions a e summa ised in Table 2. Reassessmen o he Pu by MS echniques The main p oblem when measu ing 239 Pu by ICP- SFMS appea s when U is p esen in he sample (mo- lecula isoba ic in e e ence due o he o ma ion o 238 U 1 H þ in he plasma), and also om he ailing e ec o he 238 U peak, which leads o an inc ease in he backg ound signal a m/z¼239. Some al e na- i es ha e been conside ed in he li e a u e in o de o a oid hese p oblems: one op ion consis s in using a low- low mic onebulize coupled wi h a memb ane desol a o as sample in oduc ion sys em (A idus) (6) , and he second op ion consis s in using deu e a ed wa e as sample sol en (29) . In his wo k, he in lu- ence o 238 U on he backg ound signal a m/z¼239 was in es iga ed using he A idus-ICP-SFMS. Thus, a ce i ied s anda d solu ion o 0.1 ppb o 238 Uin HNO 3 5%[( 238 U)10 5 ( 239 Pu)samples] was mea- su ed, ob aining a backg ound signal a m/z¼239 o 1.0+0.3 cps (n¼10). The backg ound signal ob ained wi h HNO 3 5 % blanks a m/z¼239 was 0.3+0.1 cps, indica ing ha he con ibu ion o 238 U o he 239 Pu signal is negligible in hese condi- ions. These esul s a e in good ag eemen wi h o he wo ks o he analysis o Pu in u ine samples (3) . Ex e nal calib a ion was employed du ing he eassessmen o 239 Pu and 242 Pu in AS planche s o A idus-ICP-SFMS analysis (Figu e 2). All he solu- ions (blanks, s anda ds and samples) we e spiked wi h 237 Np as an ex e nal s anda d, o moni o he ins umen s abili y du ing he measu emen s (Figu e 3). The esul s indica e he excellen chemical eco - e y achie ed wi h he p oposed ex ac ion p ocess o he eassessmen o Pu om AS planche s Table 2. Ins umen al condi ions op imised o he measu emen o Pu om planche s by A idus-ICP-SFMS. Solu ion up ake a e 0.1 ml min 21 RF powe 1300 W Cool gas low a e 16.0 l min 21 Auxilia y gas low a e 0.70 l min 21 Nebulize gas low a e 1.194 l min 21 Ion ex ac ion lens po en ial 22000 V Mass esolu ion (m/Dm) 300 Iso ope 237 Np; 238 U; 239 Pu; 240 Pu; 242 Pu Samples pe peak 100 Se ling ime 10 ms Sample ime 10 ms Poin s pe wid h 10 Peak shi 1.0 Mass window 100 % In eg a ion window 20 % Scan ype E-Scan De ec ion mode T iple (ion coun ing, analogue and Fa aday) To al analysis ime pe sample 3 min Sample /skimme cone Nickel A idus desol a o Sweep gas (A ): 4.57 ml min 21 Ni ogen low: 6 ml min 21 Nebulize Mic o low nebulize PFA-100 Table 1. Resul s o adiochemical yield o Pu (measu ed by AS). All he samples we e ini ially spiked wi h 8.4 pg o 242 Pu. Sample 239 Pu added ( g) a 242 Pu measu ed (pg) Reco e y yield o 242 Pu (%) 1 8 6.49+0.43 78 2 10 6.82+0.58 82 3 10 6.24+0.50 75 4 17 6.74+0.43 81 5 20 6.49+0.70 78 6 26 6.74+0.67 81 7 32 6.24+0.67 75 8 35 8.07+0.80 97 9 40 6.07+0.66 73 a239þ240 Pu measu ed is below he MDA. H. HERNA ´NDEZ-MENDOZA ET AL. 300 (Table 3). Howe e , i mus be poin ed ou ha , in he case o AMS measu emen s, he p esence o millig ams o i on coming om he planche (due o co osion) can a ec he sensi i i y o he analysis due o a dilu ion e ec on he sample (7) . The calcula ion o he 239 Pu con en in he ini ial u ine samples was pe o med by he iso ope dilu ion me hod, conside ing he 239 Pu/ 242 Pu iso opic a io measu ed by A idus-ICP-SF-MS in he Pu ac ion leached om he planche s (90 %) and he amoun o spike ini ially added o he samples; hese esul s a e shown in Table 3, column wo and he esul s we e con i med by AMS. The le els o 239 Pu concen- a ion by bo h me hods no showed signi ican di - e ence in esul s. Limi o de ec ion (LOD) and MDA o 239 Pu using A idus-ICP-SFMS we e calcula ed om he analysis o a se ies o 10 p ocedu al blanks, and compa ed wi h hose epo ed in p e ious publica- ions by AS, AMS and con en ional ICP-SFMS (Table 4) (25) . The ob ained esul s wi h he new se up a e abou one o de o magni ude lowe han hose epo ed by con en ional ICP-SFMS, and compa es wi h hose ob ained by AMS. LOD o Pu by AS was calcula ed using he Cu ie c i e ion (30) and, hen, MDA was calcula ed conside ing he LOD, he a e age chemical yield o Pu (80+7 %) and he o al olume o u ine (1725+114 ml). In he case o A idus-ICP-SFMS and AMS, he LOD and AMD calcula ions we e made as desc ibed in a p e ious wo k (7,25) . Acco dingly wi h (8) , and assuming an acu e in ake by inhala ion o a ype S subs ance, an exc e ion o 2.3 10 –6 (Bq o Pu/Bq in ake) is p edic ed a he i s day o he in ake (13) . The e o e, conside ing he MDA le els o Pu epo ed he e (7.410 26 Bq pe sample o A idus-ICP-SFMS, and 1.010 26 Bq pe sample o AMS), i can be concluded ha he me hod de eloped in his pape p o ides enough sensi i i y o pe o m he eassessmen o planche s when AS is unable o gi e any in o ma ion du ing in e nal dosime ic con ols. Minimum de ec able doses can be hen calcula ed a gi en days a e Figu e 2. Calib a ion cu es o 239 Pu and 242 Pu measu ed by A idus-ICP-SFMS. Figu e 3. Ins umen al s abili y o he A idus-ICP-SFMS, moni o ed du ing he analyses using 237 Np as ex e nal s anda d. Table 3. Reassessmen o 239 Pu on planche s by A idus- ICP-SFMS and AMS. Sample A idus-ICP-SFMS AMS 239 Pu ( g) a 239 Pu ( g) b 239 Pu ( g) b 1 5.4+0.9 8.1+1.7 8.2+0.8 2 6.5+0.8 10.1+1.7 9.8+0.6 3 7.2+0.5 10.0+1.2 10.3+0.8 4 13.7+0.7 17.1+1.7 17.4+0.9 5 13.9+0.8 20.0+2.1 19.5+0.9 6 19.3+1.2 27.1+3.0 25.8+1.4 7 22.4+1.2 32.3+3.4 31.6+1.6 8 30.6+1.4 36.1+3.4 34.8+1.3 9 27.6+1.4 40.1+4.0 38.3+1.8 a Resul ob ained o 239 Pu wi h ex e nal calib a ion by A idus-ICP-SFMS. b Calcula ed mass o 239 Pu used me hod o iso ope dilu ion me hod, conside ing he 239 Pu/ 242 Pu iso opic a io measu ed. REASSESSMENT OF 239 PU BY ARIDUS-ICP-SFMS AND AMS 301 in ake om he MDA o he me hod, u ina y exc e- ion a e (24 h u ine samples) and dose coe icien . I he u ine is collec ed on he i s day o acu e in ake o ype S 239 Pu a e an acciden , he minimum de- ec able dose o he me hod is 0.03 mS o A idus- ICP-SFMS, and 0.004 mS o AMS. One yea a e he in ake, he minimum de ec able dose o his me hod is lowe han 0.5 mS o bo h echniques. CONCLUSIONS Di e en analy ical me hods o quan i ying 239 Pu in u ine wi h MS echniques ha e been op imised and e alua ed in his pape . The esul s indica e ha hey a e sui able o dosime ic moni o ing o he s a occupa ionally exposed o Pu. The analy ical echniques employed (A idus-ICP-SFMS and AMS) ha e shown success in hese kinds o con ols, exhi- bi ing excellen sensi i i y o Pu analysis, and a e- ma kable inc ease o p oduc i i y when compa ed wi h AS. This opens he possibili y o gi ing suppo o he in e nal dosime y se ice o ou ine analysis in hose cases whe e he Pu con en is below he MDA achie ed by AS, bo h in u ine samples and in he eassessmen o planche s. FUNDING This wo k was suppo ed by he P ojec Cen o de In es igaciones Ene ge ´ icas, Medioambien ales y Tecnolo ´gicas (CIEMAT) 2007/P1423 and wi h cola- bo a ion he Cen o Nacional de Acele ado es de Se illa. REFERENCES 1. He na ´ndez-Mendoza, H., Chamizo, E., Ylle a, A., Ga cı ´a-Leo ´n, M. and Delgado, A. Measu emen o 239 Pu in u ine samples a ul a- ace le els using a 1 MV compac AMS sys em. Nucl. Ins um. Me hods Phys. Res. B 268, 1331–1333 (2010). 2. Schmi ze , C. e al.Imp o emen s in ou ine in e nal moni o ing—an o e iew o he IDEA p ojec . Radia . P o . Dosim. 125, 472–476 (2007). 3. Zo iy, M. V., Pickha d , C., Os apczuk, P., Hille, R. and Becke , J. S. De e mina ion o Pu in u ine a ul a- ace le el by sec o ield induc i ely coupled plasma mass spec ome y. In . J. Mass. Spec om. 232, 217–224 (2004). 4. Epo , V. N., Benkhedda, K., Co ne , R. J. and E ans, R. D. Rapid de e mina ion o plu onium in u ine using low injec ion on-line p econcen a ion and induc i ely coupled plasma mass spec ome y. J. Anal. A . Spec om. 20, 424–430 (2005). 5. La i ie e, D., Cumming, T. A., Kise , S., Li, C. and Co ne , R. J. Au oma ed low injec ion sys em using ex- ac ion ch oma og aphy o he de e mina ion o plu o- nium in u ine by induc i ely coupled plasma mass spec ome y.J.Anal.A .Spec om.23, 352–360 (2008). 6. Pappas, R. S., Ting, B. G. and Paschal, D. C. Rapid analysis o plu onium-239 in 1 ml o u ine by magne ic sec o induc i ely coupled plasma mass spec ome y wi h a desol a ing in oduc ion sys em. J. Anal. A . Spec om. 19, 762–766 (2004). 7. He na ´ndez-Mendoza, H., Chamizo, E., Ylle a, A., Ga cı ´a-Leo ´n, M. and Delgado, A. A highly sensi i e me hod o he eassessmen and quan i ica ion o 239 Pu in u ine samples based on a 1 MV accele a o mass spec ome y sys em. J. Anal. A . Spec om. 25, 1410–1415 (2010). 8. Kuwaba a, J. and Noguchi, H. De elopmen o apid bioassay me hod o plu onium. J. Radioanal. Nucl. Chem. 252, 273–276 (2002). 9. Rob edo, L. M., Na a o, T. and Sie a, I. Indi ec moni o ing o in e nal exposu e in he decommissioning o a nuclea powe plan in Spain. J. Appl. Radia . Iso . 53, 345–350 (2000). 10. Ha duin, J. C., Peleau, B. and Le a asseu , D. Analy ical de e mina ion o ac inides in biological samples. Radiop o ec ion 32, 229–245 (1996). 11. Hu gen, C. and Cossonne , C. A. A su ey on unce - ain y in bioassay measu emen s ca ied ou wi hin he OMINEX p ojec . Radia . P o . Dosim. 105, 375–378 (2003). 12. Gia dina, I., And eocci, L., Bazza i, S., Mancini, L. and Ba is i, P. A compa ison o di e en adiochemical me hods applicable o he de e mina ion o plu onium iso opes in u ine ia alpha spec ome y. Czech. J. Phys. 56, D265–D270 (2006). 13. In e na ional Commission on Radiological P o ec ion (ICRP). The 2007 Recommenda ions o he In e na ion- al Commission on Radiological P o ec ion. ICRP Publi- ca ion 103. Ann. ICRP 37(2–4) (2007). 14. Dai, X., Ch is l, M., K ame -T emblay, S. and Synal, H-A. Ul a- ace de e mina ion o plu onium in u ine samples using a compac accele a o mass spec ome y sys em ope a ing a 300 kV. J. Anal. A . Spec om. 27, 126–130 (2012). 15. Ellio , N. L., Bickel, G. A., Linauskas, S. H. and Pa e son, L. M. De e mina ion o em og am quan i ies o 239 Pu and 240 Pu in bioassay samples by he mal ion- iza ion mass spec ome y. J. Radioanal. Nucl. Chem. 267, 637–650 (2006). 16. Wagne , S. E. e al.P ac ical applica ion o he mal ion- iza ion mass spec ome y o he de e mina ion o Table 4. Resul s ob ained in he LODs and AMDs o Pu in human u ine samples by AS, A idus-ICP-SFMS and AMS. Me hod LOD MDA 239 Pu ( g/sample) 239 Pu ( g/sample) AS 20.2+2.2 51.1+5.2 HR-ICP-MS a 4.87+0.09 23.43+0.94 A idus-HR-ICP-MS 0.81+0.03 3.23+0.12 AMS a, b 0.20+0.08 0.44+0.16 a These da a co espond o a p e ious wo k (25) . b Da a o LOD o Pu by AMS co esponds o he ‘c i ical le el’ as de ined by Cu ie (30) as c i e ia le el¼2.33( s B 1/2), whe e s B co espond o he s anda d de ia ion o blank samples. H. HERNA ´NDEZ-MENDOZA ET AL. 302 plu onium o he LANL Bioassay P og am (LA-UR- 00–1697). J. Radioanal. Nucl. Chem. 248, 423–429 (2001). 17. P ies , N. D., Pich, G. D., Fi ield, L. K. and C esswell, R. G. Accele a o mass spec ome y o he de ec ion o ul a-low le els o plu onium in u ine, including ha exc e ed a e he inges ion o I ish sea sedimen s. Radia . Res. 152, S16–S18 (1999). 18. B own, T. A., Ma che i, A. A., Ma inelli, R. E., Cox, C. C., Knezo ich, J. P. and Hamil on, T. F. Ac inide measu emen s by accele a o mass spec ome y a Law ence Li e mo e Na ional Labo a o y. Nucl. Ins um. Me hods Phys. Res. B 223, 788–795 (2004). 19. Becke , J. S. S a e-o - he-a and p og ess in p ecise and accu a e iso ope a io measu emen s by ICP-MS and LA-ICP-MS, Plena y Lec u e. J. Anal. A . Spec om. 17, 1172–1185 (2002). 20. Hou, X. and Roos, P. C i ical compa ison o adiome - ic and mass spec ome ic me hods o he de e min- a ion o adionuclides in en i onmen al, biological and nuclea was e samples. Anal. Chim. Ac a. 608, 105–139 (2008). 21. La i ie e, D., Taylo , V. F., E ans, R. D. and Co ne , R. J. Radionuclide de e mina ion in en i onmen al samples by induc i ely coupled plasma mass spec om- e y. Spec ochimica. Ac a. Pa B 61, 877–904 (2006). 22. Becke , J. S. Ino ganic Mass Spec ome y: P inciples and Applica ions. John Wiley & Sonc Inc.416–432 (2007). 23. Vasiliades, J. Reac ion o alkaline sodium pic a e wi h c ea inine: I. Kine ics and mechanism o o ma ion o he mono-c ea inine pic ic acid complex. Clin. Chem. 22, 1164–1671 (1976). 24. Duke, K. Use o he u ina y exc e ion o c ea inine in plu onium in u ine bioassay. Radia . P o . Dosim. 79, 125–128 (1998). 25. He na ´ndez-Mendoza, H., Chamizo, E., Delgado, A., Ga cı ´a-Leo ´n, M. and Ylle a, A. Compa ison o me hods and applica ion o alpha spec ome y and mass spec- ome y echniques o 239 Pu de e mina ion in biological samples. J. Anal. A . Spec om. 26, 1509–1513 (2011). 26. Se ice P o ocol o In e nal Dosime y. Me hod using o de e mina ion o 239þ240 Pu y 238 Pu in u ine samples: PE-IA-DR-03. CIEMAT, Espan˜a, 2 (2002). 27. Ma co, R., Ka o za, E., Gonen, R., Ge man, U., Tshu a, A., Pelled, O., Paz-Tal, O., Adou , A. and Ka pas, Z. No malisa ion o spo u ine samples o 24-h collec ion o assessmen o exposu e o u anium. Radia . P o . Dosim. 130, 213–223 (2008). 28. Se ice P o ocol o In e nal Dosime y. Recep ion and accep ance o biological samples o he de e mina ion o c ea inine: PTBIO20. CIEMAT, Espan˜a 1 (2010). 29. Vais, V., Li, C. and Co ne , K. P e en ing u anium hyd ide o ma ion in s anda d u anium samples o de- e mina ion o 239 Pu by ICP-MS. J. Anal. A . Spec om. 19, 1281–1283 (2004). 30. Cu ie, L.A. Limi s o quali a i e de ec ion and quan i- a i e de e mina ion. Anal. Chem. 40, 586–593 (1968). REASSESSMENT OF 239 PU BY ARIDUS-ICP-SFMS AND AMS 303