Gsaüiiveiwibte

Gsaüiiveiwibte

'C or GSAÜIIVEIWIBTE CUflIIITIIIi MïtiTHI AJIAlfïïf ,7 -' y/ . •'• .'7. 's -i, . \ STELLINGEN BEHORENDE BIJ HEJ FROEFSCHRIffT VAN R. FURLER 1. De episoomtheorie over het ontstaan van het mitochon- drion is weinig plausibel. R.A, Ratt and H.R. Mahler, Science 221 O972),575 2, Doordat S. Cirendini et al. de dragergassnelheid aan 'aet einde van een chromatografische kolom gebruiken, ontstaat een geflatteerd beeld van de weergegeven re- sultaten. Tevens is het niet mogelijk een dragergas- snelheid te berekenen zonder dat men de interstitiële porositeit kent» S, Cirendini, J. Vermont, J.C. Gressin and CL. Guilleain , J. Chromat. 84 (1973),24 3. De in de mode zijnde bepaling van RNA-moleculair ge- wichten door metingen aan formaldehyde behandelde RNA's berust op dubieuze aannamen. J.M. Kaper and M.E. v/aterworth,Virology 51 (1973),183 T.O. Diener and D.R. Smith, Virology *£ (^973), 359 M.M. El Manna and G. Bruening, Virology 56 (1973),198 4, Op grond van de zeer grote verschillen in stralingska- rakteristiek van de isotopen 1-131 en 1-123 is het streven van isotopenproducenten om een zo 'schoon' mogelijk 1-123 voor diagnostische doeleinden te leve- ren in strijd met de volksgezondheid, doordat de ver- tragingen#die dit oplevert onnodige stralingsbelasting voor patiënten veroorzaakt. H. ïlishiyama et al. J.Nucl.Med. 1£ (1974),261 5« De analogie die Gilbert et al. opmerken tussen de "exchange peak" in de kolom vloaistofchromatografie met behulp van ionenwisselaar en de luchtpi.ek bij gaschromatografie is twijfelachtig. T.W. Gilbert and R.A, Dobbs, Analyt.Chem. 45 (1>73), 1390. ~^ 6. De aanname dat Rhizobia een tumorvormende bakterie als evolutionaire voorouder hebben gehad, die een plasmide met stikstoffixatiegenen verwierf is aan- trekkelijker dan de aanname van Dilworth en Parker dat zij een zelf-voorzienende stikstofbindende bakterie als voorouder hebben gehad. M.J. Dilworth and CA. Parker, J.Theoret. Biol. 2£ (1969),203 7. De verwijdering van thallium matrices door middel van extractie met 2,2' dichloorethoxyethaan ten behoeve van sporeanalyse levert een onvoldoende decontamina- tiefaktor. P.I. Artyukin,E.N. Gil'bert and V.A. Pronin, Trudy Kom. analit. Khim. 16 (1968)^69 J'L... INFLUENCE OF CH&MELWIDTH IR GAMMA-RAY SPECTROMETRY and two other contributions to activation analysis ACADEMISCH PROEFSCHRIFT ter verkrijging van de graad van doctor in de wiskunde en natuurwetenschappen aan de Universiteit van Amsterdam, op gezag van de Rector Magnificus Dr. A. de Froe, hoogleraar in de faculteit der geneeskunde,in het open- baar te verdedigen in de aula der universi- teit (tijdelijk in de Lutherse Kerk, ingang Singel 411, hoek Spui) op woensdag 12 juni 1974- des namiddags te 4- uur. door ROBERT FURLER geboren te amst^rdam PROMOTOR : Prof.Dr. G. den Boef GOPROMOTOR : Dr. H. Poppe CO-REFERENT: Dr.Ir. H.A. Das CONTENTS page Voorwoord I Introduction II Summary IV Samenvatting VIII A statistical approach to the choice of 1 channelwidth in gamma-ray spectrometry using empirical relations between resolution and gamma-ray energy A statistical approach to the choice of 20 channelwidth in gamma-ray spectrometry II. The use of semi-empirical relations between resolution and gamma-ray energy for Nal(Tl) scintillation detectors The exchange behaviour of inorganic thallium compounds on hydrated antimony pentoxide Electrodeposition on copper powder as a means 37 of separation for trace analysis of noble metals in activation analysis, a tracer study -I- VOORWOORD Dit proefschrift beslaat mijn werk dat in de tijd dat ik op het laboratorium voor Analytische Scheikunde heb gewerkt tot een afgerond resultaat is gekomen. Diegenen die hun heel direkte bijdrage aan de verschillende delen van dit werk gegeven hebben zijn vanzelfsprekend co-auteur van de artikelen. Anderen zijn promotor, copromo- tor en coreferent, één heeft een dubbelfunktie. Dat heeft tot gevolg dat al diegenen die op iets minder di- rekte manier hebben geholpen niet worden genoemd. Daar zou ik iets aan kunnen doen door iedereen persoonlijk in dit voorwoord te bedanken. Maar ik ben bang dat ik niet in staat ben dat te doen zonder dat het onecht klinkt. Ik doe het daarom liever niet, in de hoop dat ik iedereen die me hielp direkt heb later, merken dat ik daar blij mee was. Als dat niet altijd duidelijk is geweest, dan spijt me dat en dan wil ik alsnog zeggen dat ik iedereen voer allo hulp erg dankbaar ben. : . ••••. •' •'• • • '•• •-...: . •-il—"- •' •••. ' • • "• •-•.••;• ••' - :••••: • INTRODUCTION ! i . i i The content of this thesis can be divided into tv/o parts. The main part, consisting of two papers, deals with the influence of the choice of channelwidth on the overall i resolution in gamma-ray spectrometry. The other two papers : describe separation systems for activation analysis. In all the studies we have made, our aim was to ensure a relative simplicity in the actual application of the subject under consideration. This simplification applies to the separation systems as well as to the influence of channel- width on the gamma-ray spectrum. In analytical chemistry it is quite common to consider those factors that affect the precision of spectrometric systems. Thus, in gamma-ray spectrometry using multichannel analyzers, the influence of the radiation detectors and the electronics involved on the broadening of the gamma peak is widely recognized. Although the influence of the finite energy content of a channel of a multichannel analyser on peak-broadening is known in a qualitative way, a systematic and quantitative v treatment may be helpful in the optimization of the spectrometric system for a specific problem. We dealt with this problem for Ge(Li) and Nal(Tl) detectors in our first and second paper, using two different relations between detector resolution and gamma-ray energy. i The need for a knowledge of the precision of the measured j peak as a function of the gamma-ray energy exists especially when it is necessary to measure at the same time higher and lower energy gamma rays with a multichannel analyzer with small memory capacity. This occurs especially when one wishes to determine , palladium, silver, platinum, gold and mercury in one step by activation analysis using Nal(Tl) scintillation detectors ( and a low cost multichannel analyzer for reasons of simplicity \ and wider applicability. A separation system for these metals I b,7 means of electrodepositiön on copper powder is described h in ïthé,;- fourth paper. •.':••• ,. • .: • "' • •. 'it. -•'••. .... V/hen this separation system is applied to a thallium matrix the need arises to ensure/better matrix decontamination than can be attained by eiectrodeposition. Therefore we evaluated the possibilities of Hydrated Antimony Pentoxide : for different thallium compounds, the description of which can be found in the third paper. All research described in the four papers which form this thesis originated from the problem of determination of noble metals in thallium matrices. We hope that this contribution is a step forward towards the solution of this problem. -IV- SUMMARY f. A STATISTICAL APPROACH TO THE CHOICE OF CKANNELWIDTH IN ' GAMMA RAY SEECTROMETRY USING- EMPIRICAL RELATIONS BETWEEN" RESOLUTION AND GAMMA-RAY ENERGY R. Furler and H. Fcpp.e J. Radioanalyt. Churn. (197*0 in press In gamma-ray speetroinetry, the finite channelwidth of a multichannel analyz.er influences the resolution of gamma peaks obtained from the detector. In deciding which number of channels to USG for a certain energy range there are always two compromises to be made: first that between the largest possible energy range and the smallest number of channels, and secondly that- between the too small number of channels for the low energy gamma peaks and the too large number of channels in the high energy region. Both compromises can be made when the influence of the choice of the channelwidth on the broadness of the registered gamma peak is known. This influence can be estimated by comparing the registered peak in the histogram form as obtained from the multichannel analyzer, with the gamma peak delivered by the detector system itself. As a measure of comparison the normalized central second moment is Used. Prom this comparison it is possible to derive an expression for the extra peak-broadening " 'caused by the channelwidth and also for the channelwidth, .. once the value for the extra peak-broadening is accepted as bolerableV This expression also contains the relation between the detector line width and the gamma energy., ; For four types of Nal(Tl) scintillation detectors we' constructed; graphical straight line fits to the resolution data. Each detector was represented by two lines: cne for the lower energy and another for the higher energy part. ...t-.....-j.t ".1M-.L- •'•{ •• ...-«Slf. .L.fe.i. _._ _.. i/ƒ • For GeCLi) drift 'detectors we derived an empirical logarithmic, relation between the;energy and resolution. Graphs of the percentage of extra peak-broadening.as a. function of: channelwidth and energy are constructed as : examples of the.possible applications. Eased upon estimates it is' then-possible to test the reliability of standard' spectrum catalogues and of specimens from the literature on-activation analysis* It appeared that the extra peak-broadening is sometimes unnecessarily large and sometimes-completely negligible» in the latter case causing a rather inefficient use of spectrometer : •• •"• capacity. : . :•;'.. ..'^ "-' .'••. '•'. -• ••'. • ;.. • • <•./.•;.• . "• It is also possible for the .analyst to. achieve the ; compromise; mentioned, in .the first line in a.relatively simple way-, based on an estimate of necessary error. 2 o A STATISTICAL APPROACH TO TOE CHOICE' OF CEANNELWIDTH IN - GAMMA-RAY SPECTROMETRY II the use of semi-empirical relations between resolution and gamma-ray energy for Nal(Tl) scintillation detectors R. Furler J. Radioanalyt. Ghent., submitted for publication In the first "paper on this subject we have developed by statistical means equations describing the percentage of extra peak-broadening caused by the finite channelwidth ' 'in multichannel- gamma-ray, spëctrö'metry.

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