• Bulletin of the Korean Chemical Society
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• v.26 no.3
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• pp.393-398
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• 2005

The stability constants for the diaza-18-crown-6 ethers 2-6 and alkali metal cations ($Na^+,\;K^+,\;Rb^+\;and\;Cs^+$) were determined using potentiometry in 95% methanol. For each metal ion the stability constants of the partiallyfluorinated ligands 3-6 were larger than that of the non-fluorinated ligand 2, which might reflect an interaction between fluorine atoms and alkali metal cations. The stability constant of the ligand 4 was larger than that of the ligand 5 for each metal cation tested. This finding was also supported by the results of cation-induced chemical shifts in $^1H-,\;^{19}F$-NMR and extraction experiment. The potentiometry and NMR results as well as the X-ray crystal structures revealed that the position and number of fluorine atoms in the benzyl side arms was crucial for the enhanced interaction between a ligand and an alkali metal.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.3 no.1
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• pp.3-14
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• 2017

Nucleophilic aromatic fluorination has been one of the most explored methods in fluorin-18 based radiochemistry. Unlike electrophilic $[^{18}F]$fluorination methods, no-carrier-added nucleophilic radiofluorination with cyclotron-produced $[^{18}F]$fluoride ion offers better specific radioactivity which is essential aspect to obtain good quality images from positron emission tomography. Contrary to amenable aliphatic radiofluorination, the development of reliable aromatic $[^{18}F]$fluorination methods has been pursued by many research groups; however, no viable method has yet been established. Recently, hypervalent iodine compound draws increasing attention as versatile radiolabeling precursor for various $[^{18}F]$fluoroarenes, since it bears the capacity to introduce fluorine-18 either on electron-deficient or electron-rich aryl ring with enhanced regiospecificity. Other classes of hypervalent iodine congeners often utilized in radiochemistry are iodylarenes, iodonium ylides, and spirocyclic iodonium ylides. Recently developed spirocyclic iodonium ylides have already been avidly employed to provide various $[^{18}F]$aryl fluorides with high labeling efficiency. This metal-free protocol would afford efficient routes, replacing the traditional approaches to $[^{18}F]$fluoroarenes, from prosthetic labeling synthons to complex PET radiotracers.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.5 no.2
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• pp.145-151
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• 2019

Fluorine-18 is considered to be the radionuclide of choice for positron emission tomography (PET). Thus, the development of small molecule-based radiopharmaceuticals for use in diagnostic imaging relies heavily on efficient radiofluorination techniques. Until the early 2000s, diaryliodonium salts and aryliodonium ylides were widely employed as labeling precursors to yield aromatic PET radiotracers with cyclotron-produced [¹⁸F]fluoride ion. Rapid recent progress in the development of efficient borylation methods has led to a paradigm shift in ¹⁸F-labeling methods. In addition, deoxyfluorination has attracted a great deal of interest as an alternative approach to aryl ring activation with ¹⁸F^-. In this review, methods for radiolabel development are discussed with a specific focus on the progress made in the last 5 years. Other interesting ¹⁸F-based protocols are also briefly introduced. New methods for exploiting ¹⁸F^- are expected to increase the number of ¹⁸F-labeling methods, to allow applications in a range of chemical environments.

• Nuclear Engineering and Technology
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• v.8 no.1
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• pp.1-8
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• 1976

For tile rapid production of fluorine-18 for medical use, the up-to-date methods of separation such as the recoil separation, the alumina column chromatography, and the distillation are reviewed. The amount of the residue, the gamma emitting impurity, and the tritium content in the product obtained by each separation method are determined. The product obtained by the nuclear recoil separation or by the alumina column chromatography is inferior to that obtained by the distillation in the purity point of view. Thus, the separation by the distillation is tile most effective especially in the case of using a natural lithium carbonate target. Carrier free fluorine-18 of about 2 mCi can routinely be produced by irradiating 7g of the natural lithium carbonate under the neutron flux of about 1$\times$10$^{13}$ n/$\textrm{cm}^2$/sec for 3 hrs, and subsequent separation by the distillation. The over-all processing time is 35-40n1in.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.4 no.2
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• pp.51-56
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• 2018

Azeotropic drying process is routinely applied to enhance nucleophilicity of $[^{18}F]$fluoride ion during the nucleophilic production of PET radiotracers; however, the drying process requires usually 15-25 min. Due to the high demand of employing fluorine-18 ($t_{1/2}=109.8min$) in PET radiopharmaceutical production, several research groups have focused on the method development, obviating tedious removal process of the residual target water ($[^{18}O]H_2O$) for $[^{18}F]$fluoride ion complex to be used in radiofluorination. Some development in radiofluorination in a mixed organic solvent system was demonstrated with various aliphatic substrates, but only kryptand as a phase transfer agent was utilized in the reported method. Here, we extend to investigate the development scope of applicability with basic alkyl ammonium salt as a phase transfer agent through the extensive elution efficiency study and radiofluorination outcome for aliphatic radiofluorination.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.1 no.2
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• pp.80-87
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• 2015

Carbon-fluorine (C-F) bonds have been found ubiquitously in pharmaceuticals, radiopharmaceuticals, agrochemicals, and material science due to their unique properties such as thermal and oxidative stability and lipophilicity to improve bioavailability. For the past five years, there have been significant advances in F-18 fluorination of aromatic complex molecules combined with the development of late-stage fluorination reactions. More recently, direct incorporation of F-18 to fluorinated aromatic molecules via borylation of C-F bonds has been developed by Niwa and Hosoya. In this minireview, we will discuss the progress of C-F bondborylation of fluorinated arenes utilizing transition metal catalysts and the impact on the development of F-18 radiotracers for positron emission tomography (PET).

• The Journal of the Korea Contents Association
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• v.12 no.5
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• pp.311-322
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• 2012

Restoration materials used to investigate effects of fluorine such as enamel strengthening and anti-caries effects in several types of dental restoration materials were five kinds including Ionoseal(VOCO GmbH, Cuxhaven, Germany), Fuji Filling LC(GC Co. Tokyo, Japan), Quadrant Universal LC(CAVEX Holland BV, Netherlands), PermaCem$^{(R)}$(DMG, Hamburg, Germany) and Dyract$^{(R)}$ AP(Dentsply GmbH, Germany), and the amount of fluorine-releasing was measured with ICS-5000 Reagent-FreeTM Ion Chromatography(RFICTM, Dionex, U.S.A.). The results of this study are as follows. 1. In all types of restoration materials, the amount of fluoride-releasing was reduced with time passage and it was declined sharply to show significance in four weeks. Fuji Filling LC(12.445PPM) or resin-reinforced glass ionomer and PermaCem$^{(R)}$(16.121PPM) or compomer were found to release fluorine for a long term(P<.001). 2. Ionoseal(0.887PPM) or glass ionomer and Quadrant Universal LC(0.957PPM) or composite resin released a few fluorine of 1PPM or less than 1PPM after one week, and Dyract$^{(R)}$ AP or compomer released fluorine of 8.631PPM in one week and its amount of releasing decreased dramatically in two and four week by recording 0.175PPM and 0.116PPM, respectively. Therefore, the effect of releasing fluorine in four weeks was observed to be poor (P<.001). 3. Fuji Filling LC or resin-reinforced glass ionomer and PermaCem$^{(R)}$ or compomer released fluorine of 33.372 and 1.902PPM, respectively in one week and their amount of releasing increased to be 36.371 and 18.223PPM, respectively in two weeks. So, their amount of fluorine-releasing recorded the highest levels in two weeks(P<.001).

• Journal of the Korean Society of Radiology
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• v.15 no.7
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• pp.957-964
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• 2021

Fluorine-18 used in PET/CT scans is a radioactive isotope that emits positrons, and high energy annihilation gamma rays and beta rays cause exposure to radiation workers. In this study, as part of a plan to reduce the exposure dose of radiation workers working in the Department of Nuclear Medicine, the cause of the low shielding efficiency of Apron for F-18 was identified, and the effectiveness of the Apron double-shielded with acrylic was evaluated. L-Block, Apron+acrylic, Apron, Acrylic+Apron, and Acrylic five shields are used to measure the dose, and the tendencies were compared by performing a Monte Carlo simulation. As a result, it was found that the shielding rate of Apron double shielded with acrylic was about 4 to 8% higher than that of Apron single shielded. To the extent that it does not significantly affect the user's activity, double-shielded personal protective clothing with an appropriate acrylic thickness could help reduce radiation workers' exposure.

• Journal of the Korea Organic Resources Recycling Association
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• v.31 no.2
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• pp.5-18
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• 2023

As a result of the survey on the emission status of fluorine-based chemicals in Korea, 13 kinds of substances, including hydrogen fluoride (91%) and perfluorocarbons (5%), were emitted in workplaces. By regional groups, about 98% was emitted in the Gyeongbuk, Gyeonggi and Chungcheong regions, and about 98% in three sectors of industry related to manufacture of electronic parts, chemicals and non-metallic mineral products. The detection status of PFOS and PFOA in domestic main rivers was continuously detected in the Nakdong River, the Geum River and the Anseong Stream estuary with high fluorine-related chemical emissions, and four sites of PFOS and two sites of PFOA were detected for the first time in 2021. PFOS and PFOA were continuously detected in relatively high concentrations in the rivers where there were many semiconductor and display related sectors of industry.

• Korean Journal of Radiology
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• v.20 no.6
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• pp.997-998
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• 2019