Rapid determination of fluorine in coral skeletons by non-destructive neutron activation analysis using 20F

A rapid non-destructive technique has been proposed for the determination of fluorine in coral skeletons by thermal neutron activation analysis, using the short half-life ²⁰F nuclide (11.0 s). About 0.2-0.5 g samples were irradiated for 10 seconds in a Triga Mark II Reactor. Soon after the irradiation (25-35 s), measurements of -rays were performed with each sample and standard. The method has the drawback of low sensitivity (20 ppm of F), and the manual operation employed in the cooling step could lead to less precise measurements. We determined fluorine in coral standards within ~8% of analytical precision. The result obtained for the dolomite standard was fairly consistent with literature values, but those for the limestone standard showed to be considerably higher than the reported values. The present method was applied for the determination of fluorine in modern corals from Khang Khao Island, Thailand and Okinawa, Japan. Two core samples of an ancient reef from Funafuti Atoll were measured for fluorine to compare with modern samples. In order to understand the environmental media in which coral grew, the partition of fluorine between seawater and coral skeletons is also discussed.     

Precise,non-destructive determination of fluorine by 14-MeV neutron activation analysis

A procedure is described for the precise determination of fluorine in organic and metal-organic compounds by 14-MeV neutron activation analysis using the reaction: ¹⁹F(n,2n)¹⁸F (β +, t_{$\text{1}\text{2}$} = 110 min).A relative standard deviation of better than ±0.5% is achieved by irradiating samples and standard simultaneously. Uniform neutron exposures were ensured by rotating the samples during irradiation. Positron emitters of short half-life are allowed to decay before counting. In metal-organic compounds, Sc, Zn, Ga and Ag cause the most serious interference; for organic compounds the method is rapid, and specific for fluorine.     

The determination of fluorine in bone by fast neutron activation analysis

A routine method is presented for the determination of fluorine in small bone samples by activation analysis with fast conversion neutrons. Both the purely instrumental determination and the analysis by chemical separation are discussed. The activations are performed with the AVF cyclotron of Philips-Duphar at Petten. Use was made of a rabbit system equipped with a Be-target, which can be inserted in the internally deflected beam of the cyclotron. The sensitivity of the instrumental method is ≈1 μg. Application of chemical isolation results in a sensitivity of ≈0.1 μg.     

Nanogram determination of arsenic in biological reference materials by non-destructive Compton suppression neutron activation analysis

Summary Non-destructive epithermal neutron activation analysis in conjunction with Compton suppression has been applied to determine arsenic in seven biological standard reference materials from the National Institute of Standards and Technology. The accuracy is in excellent agreement with all the certified values and compilation results. For four of the materials detection limits between 1–4 ng/g were easily achieved while for three others they ranged from 18–50 ng/g. Overall analytical precision typically varied between 2–4% for five of the reference materials while for two other it was between 12–16%. These methods clearly demonstrate that through a judicious approach of anti-coincidence techniques, nanogram quantities of arsenic can be reliably determined without the need for labor intensive chemical separations.     

Substoichiometric and non-destructive determination of trace impurities in high-purity optical glasses by neutron activation analysis

A method of radioactivation analysis has been developed for the determination of 17 elements as impurities in high-purity optical glasses. The substoichiometric extraction of platinum with dithizone was studied and a simple procedure was proposed for the determination of platinum. Copper and manganese were also determined substoichiometrically by the extractions with dithizone and with thenoyltrifluoracetone, respectively. The non-destructive γ-ray spectrometry using a Ge(Li) detector has been applied for the determination of the other 14 elements (Ag, Co, Cr, Eu, Fe, Ir, Sc, Zn, Cs, Hf, Rb, Sb, Ta and Tb). Impurity elements at the ppb level were analysed by the proposed method and it is shown that the method is reliable for the determination of trace impurities in high-purity optical glasses.     

Fast and precise determination of fluorine in geological samples by 14 MeV neutron activation analysis

A fast and precise method of determining fluorine in geological matrices is proposed. The 0.20 MeV photopeak of¹⁹O, induced by the¹⁹F(n, p)¹⁹O reaction, was used for this assay. Neutron flux monitoring was achieved by adding an internal standard monitor (20 mg Ce) to each sample and counting the activity due to the 0.74 MeV photopeak of^139m Ce, produced in the¹⁴⁰Ce(n, 2n)^139m Ce reaction. This activity was considered to be proportional to the neutron flux during the sample irradiation. This method of fluorine determination was checked on two fluorine geological standards, mica and apatite, containing 1.50 and 2.90% fluorine, respectively. The sensitivity of the method, obviously depending upon the matrix composition, was 1.46 mg for the mica standard.     

Rapid assay of fluorine in polyethylene by neutron activation analysis

A rapid technique was developed to measure flurine incorporated into the inner surface of polyethylene containers during blow-molding. The analysis was based on the¹⁹F/n,/²⁰F reaction. Results indicate that fluorine concentrations greater than 1 g F/cm² can be measured on areas as small as 1 cm².     

Determination of fluorine in coral skeletons by instrumental neutron activation analysis

Summary A systematic and non-destructive technique is proposed for the determination of fluorine in coral samples by instrumental neutron activation analysis using the ¹⁹F(n,γ)²⁰F reaction. About 50 to 80-mg samples in polypropylene capsules were irradiated for 15 seconds in the pneumatic transfer tube system (PN-3) of JRR-3M reactor. After the irradiation at a thermal neutron flux of 1.5 ^. 10¹³ n ^. cm^{-2 .} s^-1, the coral samples and standards were cooled for 6 seconds and the g-rays emitted were measured for 15 seconds with a Ge detector. The sequence from sample irradiation to g-ray counting was performed under a computer-control mode. The analytical precision was ~5% for the JCp-1 coral standard. The present method was applied to the determination of fluorine in corals from Thailand, Okinawa and the Philippines. The advantage of one method over destructive techniques is discussed by comparing the analytical results obtained for the JCp-1 coral standard using INAA, ion chromatography and spectrophotometry. Factors that may control the levels of fluorine in corals are also discussed.     

Determination of fluorine in organic compounds by epithermal neutron activation analysis

Classical activation analysis of fluorine by thermal neutrons has a limited application because of frequent interference from chlorine, the short half life²⁰F (11.4 s) and too high dead time of detectors. A procedure is described for fluorine determination using¹⁹F (n,p)¹⁹O reaction. Use of a boron carbide shield has no effect on the activity of¹⁹O (boron ratio −1) but considerably reduces background and interference due to¹⁸O (n, γ)¹⁹O reaction. The technique has been successfully applied to the determination of fluorine in organic compounds even in the presence of large amounts of chlorine and oxygen.     

The determination of bromine in rocks by neutron activation analysis

A neutron activation method for the determination of bromine in rocks and minerals is described. After removal of iodine, bromine is separated by oxidation with potassium permanganate and extraction with carbon tetrachloride. Bromine is thon precipitated as silver bromide; yields are from 60 to 84%. The method has a sensitivity of 0.001 p.p.m. of bromine and is free from interfering reactions. The values obtained for G-1 and W-1, 0.484 and 0.490 p.p.m. of bromine respectively, are lower than the average values for granites and basalts previously reported.     

The determination of sampling constants by neutron activation analysis

It has been found that sampling constants vary greatly not only from major elements to trace elements, but also between individual trace elements. A comprehensive investigation of a potential reference material therefore requires the determination of sampling constants for all elements to be certified, and other analytical methods therefore have to be included. For methods in statistical control the described strategy can be applied.     

Fluorine analysis of standard materials by short-time activation analysis using20F

Phosphorus at trace levels alters the properties of metals and alloys. Its determination was investigated by radiochemical neutron activation analysis. Separation by solvent extraction or by evolution as P⁰ showed to be neither selective nor quantitative in presence of a metallic matrix. Therefore, a new method of separation by reduction to phosphorus hydride followed by liquid scintillation counting was investigated. This method is quantitative in the case of non-radioactive iron doped with radioactive phosphorus. At present, the separation is not quantitative for irradiated iron samples, owing probably to hot atom or radiation effects. A detection limit of 0.002 g is expected.Presented at the MTAA-8 Conference, September 16–20, 1991, Vienna, Austria.     

Multielemental determination in water by neutron activation analysis

Instrumental neutron activation analysis (INAA) technique has been applied to a water sample to determine the elemental concentrations. The sample was irradiated at a neutron flux of 1.2·10¹² n·cm^–2·s^–1 for two different periods followed by counting at three different decay times, using two coaxial type high-resolution Ge(Li) detectors. The dominant elements detected in the water sample are Ca, Cl, Na, Mg, and K present in levels while Co, I, Mn, Sm, and Sb are present in smaller amounts approximately on the average 0.01 ppm. Only traces of other elements such as rare-earth elements, Ag, As, Ba, Cu, Cd, Fe, Sr, W, Zn, seem to be present in the water samples.     

Determination of fluorine in zinc ores using an isotope neutron source based automated neutron activation analysis system

A method has been developed for routine determination of fluorine in zinc sulfide ores by activation with fast neutrons from a 6.6 Ci²²⁷Ac−Be isotope source and counting of the 4.5 to 7 MeV gamma-rays of the product nuclide¹⁶N. Samples and standards consist of pellets pressed from a mixture of powdered material with wax or graphite. Samples and standards alternate in a sequence of 20 seconds irradiation, 4 seconds decay and 20 seconds counting. This analysis sequence, including the computation of the analysis results from the counting data automated by means of a LSI-11 Microprocessor with 12K×16 bit memory. The zinc ores, containing 0.3 to 0.7% fluorine have been analysed with a precision ranging from 1.56 to 1.33% relative. As a test for the reliability of the method, three standard reference materials were analysed in the same way as the zinc ore samples.     

CAMAC-based instrumentation for a non-destructive neutron activation analysis system

The measuring system described in this paper, developed for non-destructive neutron activation analysis, consists of a semiconductor detector gamma-ray spectrometer and a sample changer coupled to a PDP-9 computer via a CAMAC interface system. CAMAC modules implemented in this system are an ADC interface, a sample changer control, display unit, a timer and a time-of-the-year clock. The spectra are accumulated in a section of the computer memory. The computer is further used for experiment control and for the analysis and interpretation of the measured gamma-ray spectra.     

The determination of rhenium in flue dust by neutron activation analysis

Rhenium was determined by radiochemical neutron activation analysis in flue dust samples of complex chemical composition. Two separation techniques were used; distillation from perchloric-hydrochloric acid solution and hydroxide scavenging followed by extraction with tetraphenylarsonium chloride in chloroform. ¹⁸⁶Re and ¹⁸⁸Re were measured with a Ge(Li) low-energy photon detector. Chemical yields were determined by reactivation. For a neutron flux of 5·10¹¹ n cm^-2 s^-1, an irradiation time of 6 h and samples of ca. l g, down to 50 p.p.b. of rhenium could be determined.     

The determination of nickel in air dust by neutron activation analysis

The determination of nickel in atmospheric aerosols, collected on filter paper, is performed by thermal neutron activation analysis using the⁶⁵Ni (T=2.56 h) isotope. Liquid-liquid extraction and anion-exchange are applied in the chemical separation. The absolute sensitivity of the method is ≌0.02 μg Ni. The relative sensitivity is 0.005 μg Ni/m³ if an air sample of about 1000 m³ is used.     

The determination of iodide in sea water by neutron activation analysis

A simple and sensitive method for the determination of iodide in sea water by neutron activation analysis has been developed. Iodide is separated from most other anions by passing sea water through a strongly basic anion-exchange column, recovered by elution with 2 M sodium nitrate, and concentrated from the eluate by precipitation as palladium(II) iodide in the presence of excess of palladium(II) with elemental palladium as carrier; elemental palladium is generated by reduction of some of the palladium(II) with thiosulfate. The precipitate is separated from the supernatant liquid by filtration. Checks on the efficiency of separation by means of added ¹²⁵I showed recoveries of 100 ± 3 %. The filter paper containing the precipitate is pressed into a pellet for neutron activation analysis by irradiation for 5 min at a flux of 4 ·10¹² n cm^?2 s^?1 and counting the ¹²⁸I 442.7-keV photopeak.