Relationship between microhardness and fluorine contents on tooth enamel determined by PIGE analysis

The remineralization effect of fluoride has been measured by surface microhardness on tooth enamel. The purpose of this study was to investigate the relationship between microhardness and fluorine concentration on tooth enamel. Twelve sound bovine enamel specimens were prepared and immersed in 0.05% NaF solution for 1, 3, 6, 24 and 36 hours, respectively. The concentration of fluorine in specimens were measured by PIGE analysis and surface microhardness of each specimen was measured by surface microhardness tester. Fluorine concentration was increased by immersing time. There was no change in microhardness of each specimen by fluorine content. The results of this study suggest that there was no relationship between the fluorine concentration and surface microhardness in sound tooth enamel. PIGE analysis can be used effectively to assess the remineralization effect of fluorine content in tooth enamel.     

Enhanced penetration of fluoride particles into bovine enamel by combining dielectrophoresis with AC electroosmosis

Fluoride deposition into the pores of enamel is necessary at high concentrations to reduce enamel demineralization and with a high degree of penetration to account for loss by ingestion. Current diffusion and electrochemical methods are inadequate for effectively transporting fluoride greater than 20 μm into enamel. The study explores the coupling of dielectrophoresis (DEP) and AC electroosmosis (ACEO) to selectively concentrate fluoride particles from fluoride gel excipients and enhance their penetration into enamel. By measuring the frequency response of approximately 10‐μm‐sized sodium fluoride particles in an aqueous gel media, appropriate frequencies for positive DEP, negative DEP, and ACEO are identified. An assembly composed of two cross‐planar interdigitated electrode (IDE) arrays with open slots is driven successively by fields at appropriate frequencies to drive fluoride particles through the slots of the IDE and into the enamel pores using a combination of DEP and ACEO methods. Fluoride uptake and penetration of 1.23% acidulated phosphate fluoride gel into bovine tooth enamel at various depths is measured using wavelength dispersive spectrometry to compare deposition by diffusion, DEP, and DEP plus ACEO. Fluoride levels in all DEP groups were significantly higher than diffusion groups at depths 10 and 20 μm. The highest fluoride concentrations at 10, 20, 50, and 100 μm depths occur under deposition conditions combining DEP with ACEO. Fluoride levels at 50 μm were equivalent to long‐term prophylactic exposure. These methods may potentially benefit populations at high risk for development of caries and periodontal disease, including underserved children and disparate groups.     

Cryolite precipitation by the Reaction of aluminium salt with sodium fluoride in aqueous solution

When aqueous solution of aluminium salt involving nitrate, chloride or sulfate was added into sodium fluoride solution, an immediate reaction occured to form cryolite-like precipitate. Examination into the resultant solution and analysis for the precipitate were carried out, leading to the fact that fluorine ion can substitute for bound water molecules around central Al⁺⁺⁺ ion, but hardly for bound hydroxide and sulfate ion which should go or be “frozen”, as it is, into cryolite-like precipitate. These ligand substitution reaction seems to contribute to identification of ion species of aluminium in aqueous solution.     

Determination of major and trace elements in bones by simultaneous PIXE/PIGE analysis

The training process and training programs in both commercial nuclear plants and Department of Energy (DOE) nuclear facilities have improved significantly in the years following the Three-Mile Island (TMI) accident. This article describes some of these changes, including the reasons behind the change, the affected population, the training accreditation process and performance-based training, and the benefits of the changes.     

Quantitative analysis of calcium and fluorine by high-sensitivity low-energy ion scattering: Calcium fluoride

Low-energy ion scattering (LEIS) probes the atomic composition of the outer surface. Well-defined reference samples are used for the quantitation. For elements like fluorine and calcium, it is not easy to find suitable, clean, and homogeneous references, since fluorine is a gas and calcium is a very reactive metal. In contrast to surface analytic techniques such as XPS, the extreme surface sensitivity of LEIS makes it difficult to use stable compounds like CaF₂ as reference, since these compounds are not homogeneous at the atomic scale. With LEIS, CaF₂ is not expected to show an atomic ratio F/Ca = 2.0. Thus, before CaF₂ can be used as reference, its atomic surface concentrations have to be determined. Here, 3-keV He⁺ scattering by a LiF(001) single crystal, an evaporated layer of Ca, and a Cu foil are used as basic references. High-purity CaF₂ is available in two forms: a single crystal and a powder. For a practical reference, powders are preferred, since if bulk impurities segregate to the surface, they will be dispersed over a large surface area. It is found that both CaF₂ (111) and powder have similar F/Ca atomic ratios. This confirms the F termination for both samples. For the powder, the F and Ca signals are reduced by 0.77 ± 0.03 in comparison with those for the single crystal. The atomic sensitivity factors and relative sensitivity factors have been determined for F, Ca, and Cu.     

Size-exclusion chromatography--multiangle laser light scattering analysis of beta-lactoglobulin and bovine serum albumin in aqueous solution with added salt

The solution characteristics of beta-LGB (beta-lactoglobulin) and BSA (bovine serum albumin) are reported as determined by size-exclusion chromatography with on-line multiangle laser light scattering, differential refractive index and UV detection. The order of the three in series placed detectors as well as the interdetector volumes have been carefully pointed out. At concentrations below 2.5 mg/ml and at different values of pH the weight-average molecular mass of both proteins have been obtained. They indicate the appearance of monomers, dimers and higher order multimers. For beta-LGB the growth of self-associates could be observed at the isoelectric point over a period of days. The range of applicability of the method is discussed.     

Determination of fluorine by proton-induced gamma-ray emission (PIGE) spectrometry in igneous and metamorphic charnockitic rocks from Rogaland (S. W. Norway)

More than 200 specimens from different occurrences of the Rogaland igneous complex and surrounding granulite facies metamorphic rocks (S. W. Norway) have been analysed by a direct non-destructive proton induced gamma-ray emission (PIGE) technique. The fluorine contents vary from <25 ppm to 3500 ppm. There is a good correlation between the concentration of fluorine and that of phosphorus for igneous rocks, suggesting a control of apatite on the F content. In metamorphic rocks, amphibole and biotite besides apatite are the principal cencentrators of fluorine indicating that fluorine in the system is controlled by granulite facies metamorphism conditions.Research Associate of the National Fund for Scientific Research (Belgium)     

Determination of calcium,phosphorus and fluorine in bone by instrumental fast neutron activation analysis

The determination of fluorine, calcium and phosphorus in bone by instrumental fast neutron activation analysis is described. Results for the IAEA standard material “Animal Bone” A3-74 re: Ca=313±10 mg/g, P=155±5 mg/g and F-613±20μg/g. The accuracy for all three elements is≤4%, precision being about 3%. The limit of determination for F is 120 μg, for Ca 30 mg and for P 1 mg in a sample of 500 mg.     

Radiotracers in fluorine chemistry. Part IX fluorination of chlorofluoroethanes by chromia catalysts treated with hydrogen fluoride or hydrogen [18F]-fluoride

Passage of dichlorotetrafluoroethane isomers or 1,1,2-trichloro- 1,2,2-trifluoroethane at temperatures ? 623 K over chromia catalysts, previously treated with hydrogen fluoride at 623 K, leads to the formation of fluorinated and chlorinated products. Incorporation of fluorine-18 radioactivity in the products is observed when hydrogen [¹⁸F]-fluoride is used in the catalyst pretreatment, indicating the involvement of a surface fluorine- containing species. The reactions observed are described in terms of series of F-for-Cl and Cl-for-F halogen exchange reactions occurring at the catalyst surface.     

Determination of minor proteins of bovine milk and colostrum by optical biosensor analysis

Automated, rapid, sensitive, and label-free biosensor-based immunoassays for immunoglobulin G (IgG), folate binding protein, lactoferrin, and lactoperoxidase in bovine milk using surface plasmon resonance optical detection with direct binding assay format are described. Samples are prepared for analysis by direct dilution into buffer. Analysis conditions, including ligand immobilization, flow rate, contact time, and regeneration are defined and nonspecific binding considerations evaluated. The technique has been applied to the measurement of these proteins in consumer milks, colostrum, milk products, and infant formulas, and their temporal change during early bovine lactation followed.     

Determination of fluorine in water samples by spiking isotope dilution and adsorption on glass beads

A rapid method for the radiometric determination of fluoride concentration in aqueous solutions is presented. The method depends on the chemisorption of HF on a glass adsorber from a dilute acid solution, which has been spiked with¹⁸F. The limit of the determination is 0.03 μg/ml. Applications to surface water and urine samples are discussed.     

Determination of fluoride by two-phase titration with triphenyltinchloride and X-ray fluorescence spectrometric end-point determination

Summary Fluoride can be precisely and accurately determined in the presence of Al(III) by the two-phase titration with triphenyltinchloride and X-ray fluorescence spectrometric end-point determination. The end-point X_eq is calculated from the coefficients of the two regression linesY (X) andY (X) obtained for two-phase mixtures with an excess of Sn and F, respectively. The relative standard deviation of the equivalence point determination is better than 0.5%, if the total concentrationY=[Sn]_ot of tin in the organic phase (1-octanol) is determined for mixtures well mixed over night at 25° C. Either the volume or the mass ratio of the aqueous fluoride and organic tin solutions may be used as the independent variable (X=V _F/V _Sn orm _F/m _Sn). F^– must be released by complexation of Al(III) with cyclohexane-diamino-tetraacetate. The correlation between the releasing power of ligands and the quality of end-point determinations and also the role of chloride, present in the aqueous phase, are discussed in detail. The solubilities of the product Ph₃SnF and the titrating substance Ph₃SnCl are 1.67·10^–4 M and 0.1497M, respectively, in pure 1-octanol at 25° C. The solubility of Ph₃SnF in the aqueous phase mostly used was 1.7·10^–5 M at 25· C.

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Fluoridbestimmung durch Zweiphasentitration mit Triphenylzinnchlorid und röntgenfluoreszenz-spektrometrische Endpunktbestimmung

Zusammenfassung Fluorid kann in Gegenwart von Al(III) durch Zweiphasen-Titration mit Triphenylzinnchlorid und röntgenfluoreszenz-spektrometrische Endpunktbestimmung präzis und genau bestimmt werden. Der Endpunkt X_eq wird aus den Regressionskoeffizienten der beiden GeradenY (X) undY (X) berechnet, welche für einen überschuß von Sn bzw. F im Zweiphasensystem erhalten werden. Die relative Standardabweichung des Äquivalenzpunktes ist besser als 0,5%, falls die totale ZinnkonzentrationY=[Sn]_ot in der organischen Phase (1-Octanol) für Mischungen bestimmt wird, welche über Nacht bei 25° C intensiv gemischt werden. Als unabhängige VariableX kann entweder das Volumen-(X=V _F/V _Sn) oder das Massenverhältnis (X=m _F/m _Sn) der wässerigen Fluoridlösung und der organischen Zinnlösung benützt werden. F^– muß durch Komplexierung von Al(III) mit Cyklohexan-diamino-tetraacetat freigesetzt werden. Die Beziehung zwischen dem Komplexierungsvermögen der Liganden und der Qualität der Endpunktbestimmungen sowie die Rolle des in der wässerigen Phase anwesenden Chlorides werden ausführlich diskutiert. Die Löslichkeit des Produktes Ph₃SnF bzw. des Titrationsmittels PhsSnCl ist 1,67·10^–4 bzw. 0,1479M in reinem 1-Octanol bei 25° C. Die Löslichkeit von Ph₃SnF in der meistverwendeten wässerigen Phase beträgt 1,7·10^–5 M.

     

Determination of kinetic parameters for pyrolysis of cellulose and cellulose treated with ammonium phosphate by differential thermal analysis and thermal gravimetric analysis

Activation energy E, pre-exponential factor k₀, and reaction order n for the pyrolysis of α-cellulose and cellulose modified with dihydrogen ammonium phosphate were determined by means of TGA and DTA. The results obtained are E = 53.5 kcal./mole, k₀ = 10^18.8 min.^?1, n = 1 for α-cellulose and E = 32 kcal./mole, k₀ = 10¹² min.^?1, n = 1 for modified cellulose. A new theory of DTA was also developed. This theory, in which it is concluded that the peak value of DTA curve coincides with the maximum rate of reaction, may be used not only for the present work but is generally applicable to DTA studies. Detailed procedures of experiment and theory are described.     

Determination of platinum and palladium in strongly acid solution by means of flow injection analysis

Microamounts of Pt(II/IV) (0.25–800 μg/ml) and Pd(II) (5–600 μg/ml) in> 0.5 M hydrochloric acid can readily be determined by means of a simple FIA method based on the selective reaction of tin(II)chloride with these metals. The FIA method has a high linear dynamic range, and is relatively free from interferences of many transition metals, with the exception of Au and Rh; small amounts of other PGMs can be tolerated. Determination of Pt on a hydrogenation catalyst by this method compares well with that found by flame atomic absorption spectroscopy. By monitoring at two or more wavelengths, Pt and Pd can be determined in mixtures by this means, to yield a simple, cost-effective FIA method for possible on-line determinations and quality control of, in particular, Pt containing acidic refinery and other process streams.     

Determination of iodate and sulphate in iodized common salt by ion chromatography with conductivity detection

A simple, rapid and accurate method for the determination of iodate in iodized common salts has been developed. The quantitative determination of iodate was accomplished by anion exchange chromatography with conductimetric detection. The method requires a sample pretreatment for the removal of large excess of chloride from the sample matrix. Onguard silver cartridges were found most suitable for this purpose. The sulphate content in the salt was simultaneously determined. The lower limits for the determination of iodate and sulphate in solution are 0.5 and 0.05 mug ml(-1), respectively. Quantitative recovery of the anions in synthetic samples has been obtained and the interferences from different cations and anions have been studied. The method has been successfully applied to the determination of iodate and sulphate in the commercially available salts. The concentrations of iodate measured by this method are in good agreement with those claimed by the manufacturer.     

Determination of total fluorine in vegetables and plants by open-flame ashing and microdiffusion : Comparison with furnace ashing and oxygen-flask combustion

The sample is ashed in a nickel crucible over an open flame with calcium hydroxide as the fixative; fluoride is separated by micro-diffusion and measured with a fluoride-selective electrode. The calcium hydroxide fixative permits a temperature of 800–850°C during the final ashing, so that insoluble silicates are decomposed and fluoride is converted to an acid-soluble form. Other advantages over furnace ashing at 600°C are less contamination and more rapid ashing (20 min compared to 6 h). The interference of aluminium and silica on microdiffusion was studied: perchloric acid was found to be preferable to sulphuric acid as medium. A new way for preparing calcium hydroxide suspension, low in fluoride, is described. The values found by the proposed method generally compare well with those obtained by oxygen flask combustion. Direct diffusion (i.e. without ashing) gave much lower values than the ashing methods, except for tea leaves.     

Oxidation of organic substances by compounds of trivalent manganese : XXV. Determination of benzene polyhydroxy and aminohydroxy derivatives with a standard solution of the fluoride complex of trivalent manganese

The redox potential of the Mn(III)/Mn(II) system in a medium of potassium fluoride and sulfuric acid was measured and its dependence on the concentration of both substances was found. Furthermore, the influence of the concentration of potassium fluoride and sulfuric acid on the visible absorption spectrum of trivalent manganese was studied.     

酸、盐处理对Pt/SAPO-11物化及其催化性能的影响

采用不同酸和盐浸渍处理SAPO-11分子筛,然后负载Pt制成改性的Pt/SAPO-11催化剂,用XRF、XRD、N_2吸附-脱附、SEM、NH_3-TPD和Py-IR对催化剂进行表征,分析其物理化学性能。结果表明,酸和盐处理没有破坏SAPO-11的骨架结构,还提高了催化剂的孔容、孔径、比表面积等性质,催化剂的酸性、酸量也明显发生了改变。在固定床反应器中,评价了改性的Pt/SAPO-11催化小桐子油一步加氢制异构烷烃性能;结合催化剂表征数据表明,颗粒粒径、比表面积、孔径、酸性和酸量影响催化剂的活性及产物分布。对比发现,经0.5 mol/L柠檬酸处理的Pt/SAPO-11催化剂孔径大小、酸性、B酸和L酸量分布合适,因此,一步加氢催化处理小桐子油性能优异;其中,生物航油组分(C_(8-16))的收率为32.47%,异构烷烃(C8-16)选择性为53.13%。