Radiochemistry Research Papers - Academia.edu (original) (raw)

Bulk atmospheric deposition of and has been measured at Versoix, close to Geneva, Switzerland. Collectors were continuously deployed from November 1997 through November 1998 for periods from 1 to 22 days depending on the frequency of... more

Bulk atmospheric deposition of and has been measured at Versoix, close to Geneva, Switzerland. Collectors were continuously deployed from November 1997 through November 1998 for periods from 1 to 22 days depending on the frequency of rain. The activities of and integrated over the sampling interval were moderately well correlated with rainfall (r2 of 0.66 and 0.55, respectively; p<0.001) and well correlated one with the other (r2 of 0.91; p<0.001). The activity ratio is close to 13.5, except for samples collected in the periods of very low precipitation which have a distinctly lower ratio. A simple model accounting for rainfall, seasonal variations and reload of the local atmosphere after a rain event explains 90% of the variance of and deposition. Concentrations of and Ca++ in rain were correlated with transport time of air masses over the continent as indicated by reconstruction of air mass trajectories over three days.

2-[(18)F]Fluoroethyl-choline ([(18)F]FECH) is a promising tracer for the detection of prostate cancer as well as brain tumors with positron emission tomography (PET). [(18)F]FECH is actively transported into mammalian cells, becomes... more

2-[(18)F]Fluoroethyl-choline ([(18)F]FECH) is a promising tracer for the detection of prostate cancer as well as brain tumors with positron emission tomography (PET). [(18)F]FECH is actively transported into mammalian cells, becomes phosphorylated by choline kinase and gets incorporated into the cell membrane after being metabolized to phosphatidylcholine. So far, its synthesis is a two-step procedure involving at least one HPLC purification step. To allow a wider dissemination of this tracer, finding a purification method avoiding HPLC is highly desirable and would result in easier accessibility and more reliable production of [(18)F]FECH. [(18)F]FECH was synthesized by reaction of 2-bromo-1-[(18)F]fluoroethane ([(18)F]BFE) with dimethylaminoethanol (DMAE) in DMSO. We applied a novel and very reliable work-up procedure for the synthesis of [(18)F]BFE. Based on a combination of three different solid-phase cartridges, the purification of [(18)F]BFE from its precursor 2-bromoethyl-4-nitrobenzenesulfonate (BENos) could be achieved without using HPLC. Following the subsequent reaction of the purified [(18)F]BFE with DMAE, the final product [(18)F]FECH was obtained as a sterile solution by passing the crude reaction mixture through a combination of two CM plus cartridges and a sterile filter. The fully automated synthesis was performed using as well a Raytest SynChrom module (Raytest, Germany) or a Scintomics HotboxIII module (Scintomics, Germany). The radiotracer [(18)F]FECH can be synthesized in reliable radiochemical yields (RCY) of 37±5% (Synchrom module) and 33±5% (Hotbox III unit) in less than 1 h using these two fully automated commercially available synthesis units without HPLC involvement for purification. Detailed quality control of the final injectable [(18)F]FECH solution proved the high radiochemical purity and the absence of Kryptofix2.2.2, DMAE and DMSO used in the course of synthesis. Sterility and bacterial endotoxin testing following standard procedures verified that the described production method for [(18)F]FECH is suitable for human applications. The routine production of [(18)F]FECH with sufficient RCYs was established by reliable and fast solid-phase extraction purifications of both the secondary labeling precursor [(18)F]BFE and the final product [(18)F]FECH, avoiding complex and sensitive HPLC equipment. The purity of the product was &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;95%, rendering the tracer suitable for human application. The newly developed purification procedure for [(18)F]BFE significantly reduces the complexity of the automated synthesis unit, hence reducing the cost for routine production in a clinical setup and allowing easy transfer to different synthesis modules.

from ebook Nuclear Chemistry Chapter 18

Karakteristik dan kegunaan Xe

Pembahasan mengenai fosil dan rumus menghitung umurnya dengan radioativitas merupakan pembahasan umum yang oleh beberapa ilmuwan sudah dibahas. Judul ini kami pilih karena mengungkap sisi lain prasejarah serta kami ingin membahas,... more

Pembahasan mengenai fosil dan rumus menghitung umurnya dengan radioativitas merupakan pembahasan umum yang oleh beberapa ilmuwan sudah dibahas. Judul ini kami pilih karena mengungkap sisi lain prasejarah serta kami ingin membahas, mengetahui sekaligus mendalami tentang bagaimana cara menghitungnya. Penelitian tentang umur fosil sebenarnya sudah lama terjadi. Mulai dengan cara sederhana yakni dengan merekonstruksi awal masa pra-sejarah hingga menggunakan radioaktivitas saat ini. Hal ini tidaklah lepas dari perkembangan zaman serta ditemukannya berbagai penemuan yang mendukung. Membahas masalah fosil tentu tidak akan ada habisnya. Namun jika kita mempelajari cara menghitung umur fosil, maka kita akan dapat memperkirakan sendiri dari zaman manakah fosil tersebut berasal. Maka dari itu, melalui makalah ini, kami mencoba untuk menggali secara jelas dan memberikan informasi mengenai cara perhitungan ini dengan baik dan akurat.

The production and radiochemical separation of 55Co from deuteron irradiation of enriched 54Fe target is described. Methods used for the recovery and reuse of the target material (54Fe) are also described. The yield of 55Co at 12 MeV... more

The production and radiochemical separation of 55Co from deuteron irradiation of enriched 54Fe target is described. Methods used for the recovery and reuse of the target material (54Fe) are also described. The yield of 55Co at 12 MeV incident deuteron energy is 1.7 mCi per mu Ah at end of bombardment and the contamination with 57Co is 0.016%. The 55Co produced is chelated to bleomycin and used for tumour imaging with a positron emission tomographic camera based on multi-wire proportional chamber detectors.

Carbon-11 labeled acetone is a useful radiosynthetic precursor. Previously, strict control of no-carrier-added stoichiometry was required to prepare it from reaction of CO2 and methyl lithium. However, excess methyl lithium may be... more

Carbon-11 labeled acetone is a useful radiosynthetic precursor. Previously, strict control of
no-carrier-added stoichiometry was required to prepare it from reaction of CO2 and methyl lithium. However,
excess methyl lithium may be selectively quenched to avoid reaction with nascent acetone to give tert-butanol.
We report a simple pKa-based strategy to sequentially and selectively quench MeLi and acetone to give yields
of up to 100% acetone even in the presence of a large excess of MeLi. The method gives good yields of acetone
under conditions that previously precluded its synthesis.

Plutonium is one of the most toxic components of spent nuclear fuel and of nuclear wastes, which is characterized by very complex chemical behaviour both in engineering processes and under environmental conditions. As a result of the... more

Plutonium is one of the most toxic components of spent nuclear fuel and of nuclear wastes, which is characterized by very
complex chemical behaviour both in engineering processes and under environmental conditions. As a result of the human
activities, plutonium is released to the environment and its speciation depends, to a large extent, on the source and release
scenario and also on the geochemical conditions. The most recent data about various sources of plutonium in the
environment and its speciation are reviewed. The recent trends in the description of one of the most important processes in
plutonium migration, i.e., its sorption onto components of soils, rocks, colloidal particles of various origin, natural organic
matter, etc., are discussed.

The row of 15 chemical elements from Ac to Lr with atomic numbers from 89 to 103 are known as the actinides, which are all radioactive. Among them, uranium and plutonium are the most important as they are used in the nuclear fuel cycle... more

The row of 15 chemical elements from Ac to Lr with atomic numbers from 89 to 103 are known as the actinides, which are all radioactive. Among them, uranium and plutonium are the most important as they are used in the nuclear fuel cycle and nuclear weapon production. Since the beginning of national nuclear programs and nuclear tests, many radioactively contaminated nuclear legacy sites, have been formed. This mini review covers the latest experimental, modeling, and case studies of plutonium and uranium migration in the environment, including the speciation of these elements and the chemical reactions that control their migration pathways.

ImmunoPET with 89Zr-labeled antibodies has shown great potential in cancer imaging. It can provide important information about the pharmacokinetics and tumor targeting properties of monoclonal antibodies and may help in anticipating on... more

ImmunoPET with 89Zr-labeled antibodies has shown great potential in cancer imaging. It can provide important information about the pharmacokinetics and tumor targeting properties of monoclonal antibodies and may help in anticipating on toxicity. Furthermore, it allows accurate dose-planning for individualized radioimmunotherapy and may aid in patient selection and early response monitoring for targeted therapies. The most commonly used chelator for 89Zr is desferrioxamine (DFO). Preclinical studies have shown that DFO is a not an ideal chelator, since the 89Zr-DFO complex is partly unstable in vivo, which results in release of 89Zr from the chelator, and subsequent accumulation of 89Zr in bone. This bone accumulation interferes with accurate interpretation and quantification of bone uptake on PET images. Therefore, there is a need for novel chelators that allow more stable complexation of 89Zr. In this review we will describe the most recent developments in 89Zr-radiochemistry, incl...

The photochemical reactions of a series of triaryl vinyl halides 1X in acetic acid and in acetonitrile have been studied using product analysis as a function of the time of irradiation. The quantum efficiencies of formation of the... more

The photochemical reactions of a series of triaryl vinyl halides 1X in acetic acid and in acetonitrile have been studied using product analysis as a function of the time of irradiation. The quantum efficiencies of formation of the products derived from the photogenerated vinyl cations 1+ depend on the α-aryl substituent, the β-aryl substituent, the leaving group X (= bromide or chloride), and the temperature at which the irradiations are carried out. Hammett correlation or noncorrelation of the α-aryl substituent effects with (excited-state) substituent constants indicates that the ions 1+ are formed directly from the excited states of 1X by heterolytic cleavage of the carbon−halogen bond. Homolytic cleavage, yielding radicals 1•, is a parallel process: the partitioning into ion and radical occurs in the excited state. This conclusion is corroborated by the leaving group effect and the temperature effect. By performing the photochemical reactions of 1X in the presence of HOAc and/or NaOAc as well as the labeled common halide ion 82Br− or 36Cl−, the relative reactivities of the cations 1+ toward these nucleophiles were determined. The selectivities follow the Reactivity−Selectivity Principle. The temperature effect data show that the reactions of the cations with the anionic nucleophiles are (de)solvation controlled and their reactions with the neutral nucleophile activation controlled.