Fluorine determination in human and animal bones by particle-induced gamma-ray emission

Fluorine was determined in the iliac crest bones of patients and in ribs collected from post-mortem investigations by particle-induced gamma-ray emission based on the ¹⁹F(p,p′γ)¹⁹F reaction, using 2.0/2.5 MeV protons. The results indicate that for 68% of the human samples the F concentration is in the range 500–1999 μg g^–1. For comparison purposes fluorine was also determined in some animal bones; in some animal tissues lateral profiles of fluorine were measured.     

Application of prompt activation analysis in the determination of fluorine in tea,in international geochemical standards,bones and teeth of experimental animals

By making use of the ¹⁹F(p,αγ)¹⁶O reaction the F-concentrations of different varieties of tea leaves, of some international geochemical reference materials, and of the bones and teeth of some experimental animals have been determined. The tea leaves from Ceylon (ordinary), Orange Pekoe (special Ceylon), China (ordinary black), Lapsang Souchong (special smoked Chinese) and Darjeeling (India) were found to contain 170 ppm, 170 ppm, 120 ppm, 160 ppm and 100 ppm of fluorine, respectively, The F-concentrations of established geochemical reference materials, NIM-D, NIM-N, NIM-P and NIM-S, from the National Institute of Metallurgy, South Africa were determined to be 60 ppm, 120 ppm, 130 ppm and 190 ppm, respectively. The bones of rabbits, who were given fluoridated water, were found to contain much higher amount of fluorine than the bones of the control rabbit. Furthermore, the rabbits who were kept on fluoridated water for 45 days, had almost double the amount of F in their bones than the rabbits who were given fluoridated water for only 15 days. Similarly, the teeth of grown-up monkeys who were given fluoridated water since birth had double the amount of fluorine than those of the control monkey.     

Trace analysis of fluorine by the Coulomb excitation method

The reaction¹⁹F(p, p′ γ)¹⁹F was used for the determination of fluorine concentration in biological materials such as lichen tissues and human bones. By means of this method, fluorine air contamination in the vicinity of aluminium works and the level of fluorine intoxication of exposed persons were investigated.     

The mechanism of base-promoted HF elimination from 4-fluoro-4-(4-nitrophenyl)butan-2-one is E1cB. evidence from double isotopic fractionation experiments

Leaving-group fluorine and secondary deuterium multiple kinetic isotope effects (KIEs) have been determined for the base-promoted HF elimination from the 4-fluoro-4-(4'-nitrophenyl)-(1,1,1,3,3-(2)H(5))butan-2-one. The fluorine KIE was determined by using the accelerator-produced short-lived radionuclide (18)F in combination with the naturally abundant (19)F. The (19)F substrate was labeled with (14)C in a remote position to enable radioactivity measurements of both substrates. The size of the determined fluorine KIE is 1.0009 +/- 0.0010 when acetate is used as base. The secondary deuterium KIEs are 1.009 +/- 0.017, 1.000 +/- 0.018, and 1.010 +/- 0.023 for formate, acetate, and imidazole, respectively. The magnitudes of these KIEs are significantly smaller compared to the corresponding KIEs that we recently reported for the protic substrate. This new data clearly demonstrates that the elimination proceeds via an E1cB mechanism.     

The mechanism of base-promoted HF elimination from 4-fluoro-4-(4'-nitrophenyl)butan-2-one: a multiple isotope effect study including the leaving group (18)F/(19)F KIE.

Leaving-group fluorine as well as the primary and secondary deuterium kinetic isotope effects (KIEs) have been determined for the base-promoted elimination of hydrogen fluoride from 4-fluoro-4-(4'-nitrophenyl)butan-2-one in aqueous solution. The elimination was studied for formate, acetate, and imidazole as the catalyzing base. The fluorine KIEs were determined using the accelerator-produced short-lived radionuclide (18)F in combination with natural (19)F. The (19)F substrate was labeled with (14)C in a remote position to enable radioactivity measurement of both isotopic substrates. The elimination reaction exhibits large primary deuterium KIEs: 3.2, 3.7, and 7.5 for formate, acetate, and imidazole, respectively, thus excluding the E1 mechanism. The corresponding C(4)-secondary deuterium KIEs are 1.038, 1.050 and 1.014 and the leaving group fluorine KIEs are 1.0037, 1.0047 and 1.0013, respectively. The size of the fluorine KIEs corresponds to 5-15% of the estimated maximum of 1.03 for complete C-F bond breakage. No H/D exchange is observed during the reaction. The size and trends of the KIEs for the different bases are consistent with an E1cB-like E2 or an E1cB(ip) mechanism.     

A method for charged-particle activation analysis and its application to fluorine determination by the19F(p, αγ)16O reaction

A simple method for calculating the sensitivity for detecting a nuclide distributed uniformly in any given matrix through charged particle activation is described. This method takes into account the actual values of the reaction cross section at different energies as the beam traverses through a thick target and the corresponding stopping power values. The detection sensitivity for fluorine in a number of matrices through the¹⁹F(p, αγ)¹⁶O reaction have been calculated as a function of the energy from threshold to 4.16 MeV using this method and the sensitivity curves plotted. The sensitivity values (dps/ppm/μA) for a thick or thin target and even for a layer of known thickness at a particular depth within a sample can be directly read from these curves for known bombarding conditions. The comparator methods for charged particle activation analysis of RICCI¹ and of CHAUDHRI,² especially when the matrices of the sample and standard are different, have been compared in the case of F determination through the¹⁹F(p, αγ)¹⁶O reaction. It has been found that the errors are reduced by almost a factor of two when the latter method is used compared to the former one. The fluorine concentration in animal bones and teeth, apatite crystal, and rocks have been determined through the¹⁹F(p, αγ)¹⁶O reaction using the Melbourne University Pelletron.     

EPR and solid-state NMR studies of poly(dicarbon monofluoride) (C2F)n

Poly(dicarbon monofluoride) (C2F)n was studied by electron paramagnetic resonance (EPR) and solid-state nuclear magnetic resonance (NMR). The effects of physisorbed oxygen on the EPR and NMR relaxation were underlined and extrapolated to poly(carbon monofluoride) (CF)n and semi-covalent graphite fluoride prepared at room temperature. Physisorbed oxygen molecules are shown to be an important mechanism of both electronic and nuclear relaxations, resulting in apparent spin-lattice relaxation time and line width during NMR and EPR measurements, respectively. The effect of paramagnetic centers on the 19F spin-lattice relaxation was underlined in accordance with the high electron spin density determined by EPR. 19F magic angle spinning (MAS) NMR, 13C MAS NMR, and 13C MAS NMR with 19F to 13C cross polarization (CP) underline the presence of two types of carbon atoms, both sp3 hybridized: some covalently bonded to fluorine and the others linked exclusively to carbon atoms. Finally, a C-F bond length of 0.138 +/- 0.002 nm has been determined thanks to the re-introduction of dipolar coupling using cross polarization.     

19F n.m.r spectra of polyfluoroquinolines. Long range inter-ring 19F?19F coupling constants and 19F chemical shifts

The signs and magnitudes of every fluorine–fluorine coupling constant in perfluoroquinoline ( 1 ), 2,4-dichloropentafluoroquinoline ( 2 ) and 2-bromohexafluoroquinoline ( 3 ) have been determined by ¹⁹F n.m.r. These provide an unambiguous assignment of the spectrum of the first compound and its derivatives. Inter-ring fluorine–fluorine coupling constants were found to be positive over an odd number of bonds and negative over an even number of bonds, similar to that observed in proton–proton coupling constants in multicyclic systems. The ¹⁹F chemical shifts of perfluoroquinoline and its protonated salt are reported and directly correlated with SCF MO calculated π-electron densities at both fluorine and bonded carbon atoms.     

Determination of Fluorine in Vegetation by Proton Activation Analysis

Abstract

Techniques have been developed for proton activation analysis using the ¹⁹F(p,p′y)¹⁹F reaction to measure the fluorine content of pulverized samples of vegetation which have been exposed to fluorides in the atmosphere or soil. The method is non-destructive and neither the chemical form of fluorine in the sample nor the type of vegetation analyzed appears to affect results. Calibration is performed by analyzing samples to which known amounts of fluorine are added. The fluorine content of 11 vegetation samples was determined by proton activation analysis and by standard chemical techniques. The values obtained by the two methods were in generally good agreement. Fluorine concentrations greater than 1 ppm can be measured with uncertainties ranging from about 50% at 5 ppm to less than 10% at concentrations above 50 ppm.     

含氟内酯的核磁共振结构分析

利用核磁共振中^1H、^13C和^19F谱以及二维技术对含氟内酯的结构及空间构型进行了研究，并对全部谱峰进行了归属，为含氟内酯合成反应的顺利进行提供了理论依据。     

The Osmium(VIII) Oxofluoro Cations OsO(2)F(3)(+) and F(cis-OsO(2)F(3))(2)(+): Syntheses, Characterization by (19)F NMR Spectroscopy and Raman Spectroscopy, X-ray Crystal Structure of F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-), and Density Functional Theory Calculations of OsO(2)F(3)(+), ReO(2)F(3), and F(cis-OsO(2)F(3))(2)(+)

Osmium dioxide tetrafluoride, cis-OsO(2)F(4), reacts with the strong fluoride ion acceptors AsF(5) and SbF(5) in anhydrous HF and SbF(5) solutions to form orange salts. Raman spectra are consistent with the formation of the fluorine-bridged diosmium cation F(cis-OsO(2)F(3))(2)(+), as the AsF(6)(-) and Sb(2)F(11)(-) salts, respectively. The (19)F NMR spectra of the salts in HF solution are exchange-averaged singlets occurring at higher frequency than those of the fluorine environments of cis-OsO(2)F(4). The F(cis-OsO(2)F(3))(2)(+)Sb(2)F(11)(-) salt crystallizes in the orthorhombic space group Imma. At -107 degrees C, a = 12.838(3) ?, b = 10.667(2) ?, c = 11.323(2) ?, V = 1550.7(8) ?(3), and Z = 4. Refinement converged with R = 0.0469 [R(w) = 0.0500]. The crystal structure consists of discrete fluorine-bridged F(cis-OsO(2)F(3))(2)(+) and Sb(2)F(11)(-) ions in which the fluorine bridge of the F(cis-OsO(2)F(3))(2)(+) cation is trans to an oxygen atom (Os-O 1.676 ?) of each OsO(2)F(3) group. The angle at the bridge is 155.2(8) degrees with a bridging Os---F(b) distance of 2.086(3) ?. Two terminal fluorine atoms (Os-F 1.821 ?) are cis to the two oxygen atoms (Os-O 1.750 ?), and two terminal fluorine atoms of the OsO(2)F(3) group are trans to one another (1.813 ?). The OsO(2)F(3)(+) cation was characterized by (19)F NMR and by Raman spectroscopy in neat SbF(5) solution but was not isolable in the solid state. The NMR and Raman spectroscopic findings are consistent with a trigonal bipyramidal cation in which the oxygen atoms and a fluorine atom occupy the equatorial plane and two fluorine atoms are in axial positions. Density functional theory calculations show that the crystallographic structure of F(cis-OsO(2)F(3))(2)(+) is the energy-minimized structure and the energy-minimized structures of the OsO(2)F(3)(+) cation and ReO(2)F(3) are trigonal bipyramidal having C(2)(v)() point symmetry. Attempts to prepare the OsOF(5)(+) cation by oxidative fluorination of cis-OsO(2)F(4) with KrF(+)AsF(6)(-) in anhydrous HF proved unsuccessful.     

Prototropic processes in benzaurins. <Superscript>19</Superscript>F and <Superscript>1</Superscript>H NMR spectra of fluoro- and methylsubstituted 4-hydroxyphenyl-diphenylcarbinols,related fuchsones and benzaurins

Tautomerism of benzaurins and hydration are studied. ¹H and ¹⁹F chemical shifts have been determined for a number of substituted 4-hydroxyphenyl-diphenyl carbinols containing fluorine in a 3-, 3*- or 4*-position, and for similar compounds containing additional methyl groups in a position of 3, 3** or 4**. The same data have been obtained for the fuchsones prepared by dehydration of the above carbinols. On this basis chemical shifts of fluorine in different positions have been evaluated as a monitor of the transformation of 4-hydroxyphenyl group to the semiquinone moiety. The ¹⁹F NMR can be used to monitor the transformation of 4**-fluorobenzaurin and the related 3,3*-disubstituted and 3,3*,5,5*-tetramethylsubstituted compounds to the corresponding carbinols due to the addition of a water molecule and to study the tautomerism of the two latter benzaurins as well as that of 3,3*,4**trifluorobenzaurin. Furthermore, fluorine and methyl group chemical shifts are sensitive to syn-anti-isomerism in substituted fuchsones.     

The potential of 19F NMR spectroscopy for rapid screening of cell cultures for models of mammalian drug metabolism

The use of microbial cultures as a complementary model for mammalian drug metabolism has been well established previously. Here is a preliminary investigation into the potential of 19F NMR spectroscopy as a rapid screening tool to quantify the biotransformations of fluorine-containing model drugs. Biotransformations of three model drugs in 48 taxonomically diverse organisms were measured by acquiring 19F NMR spectra at 376 MHz. The presence of fluorine in the molecules allowed rapid, simultaneous detection of over 20 biotransformation products without sample pretreatment, chromatography, mass spectrometric techniques or the use of radiolabelled substrates. The detection limit at 376 MHz using 5 mm NMR tubes was ca. 0.3 microg ml(-1) using a typical analysis time of 20 min per sample. With the recent advent of flow injection NMR technology, analysis time of 5 min could be achieved with less sample. This approach may be used to develop fast small-scale microbial screens for the biosynthesis of metabolite standards and production of novel drug analogues, whilst also having a role in reducing animal experiments needed to identify animal and human metabolites of fluorinated xenobiotics.     

Stabilization of molecular LiF and LiFHF inside metallamacrocyclic hosts

Complexes of molecular LiF and LiFHF were synthesized using the metallamacrocyclic receptors [(cymene)Ru(C(5)H(3)NO(2))](3) (1), [CpRh(C(5)H(3)NO(2))](3) (2), and [CpIr(C(5)H(3)NO(2))](3) (3). LiBF(4) complexes of 1-3 were prepared and subsequently treated with F(-) or FHF(-) to give the desired products in an anion-exchange reaction. All complexes were characterized by multinuclear NMR spectroscopy ((1)H, (13)C, (19)F, (7)Li). Strong scalar coupling between (7)Li and (19)F is observed for the LiF and the LiFHF complexes ((1)J(LiF) = 91-103 Hz). The LiFHF adduct of 1 displays fluxional behavior with fast exchange of the two fluorine atoms. The structures of the complexes 1.LiBF(4), 2.LiBF(4), 1.LiF, 2.LiF, 1.LiFHF, and 3.LiFHF were determined by single-crystal X-ray analysis. Li-F bond lengths between 1.77 and 1.81 A were found. The LiFHF complexes show a hydrogen difluoride anion coordinated in a bent fashion via one fluorine atom to the lithium ion.     

Resolving the different dynamics of the fluorine sublattices in the anionic conductor BaSnF(4) by using high-resolution MAS NMR techniques

19F and (119)Sn MAS NMR spectroscopy have been used to investigate the fluoride ion conductor, BaSnF(4), a member of the MSnF(4) family of fluorite-related anionic conductors containing double layers of Sn(2+) and M(2+) cations. Two fluorine sublattices were observed by (19)F MAS NMR, which could be assigned to specific sites in the lattice. The first sublattice is due to fluorine atoms located in Ba(2+) double layers and is rigid on the MAS NMR time scale at room temperature. The second sublattice comprises the fluoride ions between the Ba(2+) and Sn(2+) layers, and the few fluorine atoms that inhabit the Sn(2+)-Sn(2+) double layers. These ions are in rapid exchange with each other, and an extremely short correlation time tau(C) for the motion of these ions of <3 x 10(-)(5) s is obtained at -100 degrees C. T(1) measurements indicate that tau(C) approaches 10(-)(8) s at room temperature. (19)F-to-(119)Sn cross-polarization (CP) experiments confirmed the assignments of the resonances, and that the fluorine atoms located next to the tin atoms are extremely mobile at room temperature (and thus do not contribute to the CP process). Two-dimensional (19)F exchange experiments showed that exchange between the rigid and mobile lattice does occur, but at a much slower rate (tau(C) approximately 10 ms at 250 degrees C). Low-temperature (19)F MAS and (19)F-to-(119)Sn CP NMR spectra demonstrate that the motion of the fluoride ions has almost completely frozen out by -150 degrees C. The results are consistent with rapid two-dimensional (anisotropic) conductivity involving the fluoride ions between the Ba and Sn layers. Conductivity in three dimensions requires hops between the ions in the BaF(2)-like layers and the mobile ions. This process does occur, but with exchange rates that are at least 6-7 orders of magnitude slower.     

Epithermal/Fast Neutron Cyclic Activation Analysis for the Determination of Fluorine in Environmental and Industrial Materials

Pseudocyclic activation analysis (12-second irradiation, 12-second count, 5 cycles, 25 minutes between cycles) is used to determine fluorine in plastic and rubber with detection limits in the range 15–40 mg/kg. The detection of fluorine in materials containing high concentrations of aluminum is improved using the ¹⁹F(n,p)¹⁹O reaction, induced by fast neutrons, (30-second irradiation, 30-second count, 25-minute decay between cycles). The method was applied to a biomonitoring survey in the vicinity of an aluminum smelter in the Årdal region, Norway. The fluorine concentration in the moss and soil samples could be determined in all samples above the detection limits of 50 and 100 mg/kg, respectively.     

A nondestructive method for age determination of fossile bone

Using neutron activation the nitrogen and fluorine contents in fossile bones could be measured relative to main constituents of the inorganic bone material (phosphorus and calcium). By determining the ratio of N and F a relative and absolute age determination was possible. The method is relatively simple, quick, cheap and nondestructive.     

Weak interactions involving organic fluorine: a comparative study of the crystal packing in substituted isoquinolines

Weak interactions involving fluorine have been analyzed in the structure of 6-methoxy-1,2-diphenyl-1,2,3,4-tetrahydroisoquinoline with fluorine substitution at para-, meta- and ortho- positions, respectively, on the 1-phenyl ring. The packing modes in the crystalline lattice as determined by X-ray diffraction techniques generate motifs via F?F, C-H?F and C-F?π interactions. The three structures as compared to the parent compound depict conformational changes in the saturated tetrahydroisoquinoline moiety. The salient features of the four structures in terms of weak interactions involving fluorine suggest that organic fluorine does resemble the other halogens.     

Kinetics of chlorine isotope exchange reaction between sodium chloride-36 and triphenyltin chloride in mixed solvents

Fluorine is an important trace element for life and human well-being. Food, in general, provides about 40 percent of the fluorine intake in the human body. In order to measure fluorine levels in human diet samples, Instrumental Neutron Activation Analysis (INAA) and Proton Induced Gamma-ray Emission (PIGE) analysis were used. Reactions¹⁹F(n,)²⁰F and¹⁹F(n, p)¹⁹O were employed for determination of the fluorine concentration using a reactor neutron spectrum and epithermal neutrons. Corrections were made for the sodium matrix interference caused by the²³Na(n, )²⁰F threshold reaction in the case of reactor neutron cyclic activation analysis and for the oxygen interference via¹⁸O(n, )¹⁹O reaction when using the epithermal cyclic NAA method. The fluorine content of the diet samples was also determined by PIGE analysis making use of the resonance reaction¹⁹F(p, )¹⁶O at 872 keV. Cyclic Neutron Activation Analysis (CNAA) when combined with mass fractionation was found to be the most suitable for determination of low concentration of fluorine, through the¹⁹F(n, )²⁰F reaction with a detection limit of 2.2 ppm in Bowen's Kale elemental standard.     

Structural role of fluoride in aluminophosphate sol-gel glasses: high-resolution double-resonance NMR studies

The local structure of Na-Al-P-O-F glasses, prepared by a novel sol-gel route, was extensively investigated by advanced solid-state NMR techniques. 27Al{19F} rotational echo double resonance (REDOR) results indicate that the F incorporated into aluminophosphate glass is preferentially bonded to octahedral Al units and results in a significant increase in the concentration of six-coordinated aluminum. The extent of Al-F and Al-O-P connectivities are quantified consistently by analyzing 27Al{31P} and 27Al{19F} REDOR NMR data. Two distinct types of fluorine species were identified and characterized by various 19F{27Al}, 19F{23Na}, and 19F{31P} double resonance experiments, which were able to support peak assignments to bridging (Al-F-Al, -140 ppm) and terminal (Al-F, -170 ppm) units. On the basis of the detailed quantitative dipole-dipole coupling information obtained, a comprehensive structural model for these glasses is presented, detailing the structural speciation as a function of composition.