Problems related to gaseous fluoride wastes in brick and ceramic industry

The acquisition of data relevant to gaseous fluoride wastes in Slovenia was started in our laboratory four years ago with the intention to find out the quantities of particular fluoride wastes and the best way for their treatment or disposition.From the collected data it is obvious that brick and ceramic industry are among the worst pollutants. The clay from the majority of Slovenian clay pits was characterized. The concentrations of fluoride wastes released from the raw bricks during the firing were measured in different temperature regions. The large fluctuations of fluoride emission values, observed in chimney gases from brick-kilns are discussed and explained.     

Extractive radiometric procedure for the estimation of fluoride

A radiochemical method for the determination of fluoride has been developed. The effect of fluoride on the extraction of the Fe/III/ thiocyanate complex into TBP in nitrobenzene has been utilized. Microgram quantities of F^– have been determined. Effect of diverse ions has also been reported. The method is applied for the determination of F^– in a natural sample of apetite.     

Determination of total fluorine in blood at trace concentration levels by the Wickbold decomposition method with direct potentiometric detection

The Wickbold decomposition method in combination with differential potentiometric detection via fluoride ion-selective electrode has been applied to analysis of total fluorine in biological matrices. The performance of the method has been evaluated for determination of total fluorine in rat blood. Total mineralization of the biological sample is achieved by combustion of the sample in oxygen/hydrogen flame and subsequent absorption of the resulting fluoride in aqueous absorption medium. The fluoride is then quantified by highly selective automated differential static potentiometry with fluoride ion-selective electrode. Total fluorine determination has been evaluated in terms of sample carryover, reproducibility, precision, as well as feasibility to routine analysis of alternative biological matrices. Our results indicate that, up to 100 ppm fluorine in blood, the method does not suffer from sample carryover. Limits of quantitation of 0.5 ppm and limits of detection of 0.24 ppm fluorine in 0.5 g blood samples were achieved by elimination of inherent limitations of fluoride ion-selective electrode detection via automated differential static potentiometric measurements. The Wickbold decomposition method was found to be suitable for routine total fluorine determination in blood samples despite its relatively low throughput and high operator skill requirements.     

Capillary electrophoresis with contactless conductivity detection for the quantification of fluoride in lithium ion battery electrolytes and in ionic liquids—A comparison to the results gained with a fluoride ion‐selective electrode

In this study, an optimized method using capillary electrophoresis (CE) with a direct contactless conductivity detector (C⁴D) for a new application field is presented for the quantification of fluoride in common used lithium ion battery (LIB) electrolyte using LiPF₆ in organic carbonate solvents and in ionic liquids (ILs) after contacted to Li metal. The method development for finding the right buffer and the suitable CE conditions for the quantification of fluoride was investigated. The results of the concentration of fluoride in different LIB electrolyte samples were compared to the results from the ion‐selective electrode (ISE). The relative standard deviations (RSDs) and recovery rates for fluoride were obtained with a very high accuracy in both methods. The results of the fluoride concentration in the LIB electrolytes were in very good agreement for both methods. In addition, the limit of detection (LOD) and limit of quantification (LOQ) values were determined for the CE method. The CE method has been applied also for the quantification of fluoride in ILs. In the fresh IL sample, the concentration of fluoride was under the LOD. Another sample of the IL mixed with Li metal has been investigated as well. It was possible to quantify the fluoride concentration in this sample.     

A New Method for the Preparation of Sulphuryl Chloro Fluoride

It has been observed that a suspension of sodium fluoride in boiling acetonitrile could be used for the preparation of fluorine compounds such as silicon tetrafluoride [1], thiophosphoryl fluoride [2], sulphur tetrafluoride [3,4], and fluorocyclophosphazenes [5]. This method, when adopted for the fluorination of sulphuryl chloride [6], it is observed that a mixture of sulphuryl fluoride and sulphuryl chloro fluoride is obtained. On the other hand, when lead fluoride is substituted for sodium fluoride, pure sulphuryl chloro fluoride is evolved. Based on this observation, a new method has been standardised for the preparation of a pure sample of sulphuryl chlorofluoride by fluorinating sulphuryl chloride by lead fluoride in acetonitrile medium.     

Microscopy, porosimetry and chemical analysis to estimate the firing temperature of some archaeological pottery shreds from India

In recent times, science and technology have been applied to the world of cultural heritage, preservation and conservation. In the present study, the pottery samples belonging to 4th century were collected from Tandikkudi in Dindugul district of Tamilnadu, India and were subjected to chemical analysis to outline the information about the raw materials and technological–productive aspect such as firing temperature. Investigations such as Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM/EDS) are also done for the accurate observation of the morphology and the qualitative and Semi-quantitative determination of the chemical elements present in the sample. The firing temperature of the samples at the time of manufacturing is also estimated from apparent porosity of the samples which agrees well with the SEM analysis. The results obtained from different analytical techniques on pottery shreds provide information of the firing temperature of the pottery which lies in the range of 800 °C–1000 °C in the oxidizing atmosphere. Moreover it was observed that the samples collected from this site are low refractory in nature and the artisans of Tandikkudi have used both calcareous and non-calcareous clays for their household utilities, but were unaware of firing their artifacts at reduced atmosphere or closed kiln. Hence this paper is a useful analytical tool for predicting the firing atmosphere, type of clay (calcareous, non calcareous) and its nature (fine and coarse). Hence this paper is suitable for estimating the firing temperature of ancient potteries.     

Determination of fluoride in natural waters by ion-selective electrode potentiometry after co-precipitation with aluminium phosphate

The most effective conditions for masking aluminium in the determination of mug/1. levels of fluoride in water by ion-selective electrode potentiometry after co-precipitation with aluminium phosphate have been re-examined. The effectiveness of citrate for masking aluminium increases with pH, and up to 1.5 x 10(-2)M aluminium can be masked quantitatively at pH 8.5. Fluoride (5-100 mug in 500 ml of sample solution) is quantitatively co-precipitated at pH 4.7 with approximately 90 mg of aluminium phosphate. After dissolution of the precipitate and adjustment of the solution to pH 8.5 with TISAB, the fluoride content can be measured with a fluoride ISE. The method is simple and rapid, and is suitable for the determination of trace amounts of fluoride in various water samples.     

Phosphate rock treatment with citric acid for the rapid potentiometric determination of fluoride with ion-selective electrode

A fast method for sample treatment of phosphate rock has been developed for the purpose of quantitative leaching (98-100%) of fluoride but less of the interfering cations such as iron and aluminum. Citric acid (0.5 M) was used to extract fluoride in 15-45 min. Leaching of iron and aluminum is minimal, and these ions are complexed with citric acid. The leaching method was optimized with respect to sample size, citric acid concentration, leaching time and temperature. The analysis was completed by the rapid determination of fluoride with ion-selective electrode. The proposed treatment method was applied to phosphate rock samples from Jordan and Morocco and yielded accurate results as compared to the standard steam distillation from strong acid solution followed by thorium nitrate titration.     

Determination of fluoride after direct separation from acid medium by collection of its volatile compounds

A method is proposed for determination of fluoride by separation in acid medium followed by ion-selective electrode measurement. The separation is done at temperatures up to 200 °C, without any previous treatment of the sample, in a PTFE reactor designed to ensure the complete absorption of volatile fluoride compounds. The distillation variables (temperature, time and acid concentration) have been optimized and the interference of other various species in the separation step has been studied. The method has been applied to geological samples. The results obtained are statistically satisfactory.     

Decomposition procedure with aqua regia and hydrofluoric acid at room temperature for the spectrophotometric determination of phosphorus in rocks and minerals

A rapid spectrophotometric method for the determination of phosphorus in rocks and minerals is described. The sample solution is prepared by treatment with hydrofluoric and aqua regia at room temperature. Unreacted fluoride ions are complexed with boric acid. As fluoride ions do not have to be removed by heating, the method is rapid and avoids the use of platinum ware.     

Determination of mercury by differential-pulse anodic-stripping voltammetry with various working electrodes Application to the analysis of natural water sediments

Four types of working electrode (glassy-carbon and gold rotating-disk electrodes and two types of gold-film electrode) have been used in determination of traces of mercury by differential-pulse anodic-stripping voltammetry, and the analytical parameters of the procedures compared. The technique has been applied to the analysis of river sediments. The lowest limit of detection (0.02 μg/l.) was obtained with the gold rotating-disk electrode. Two procedures have been found optimal for analyses of sediment samples; determination with the gold rotating-disk electrode and solution-exchange after the preelectrolysis, and determination with the gold-film electrode prepared in situ in the sample extract. The sample pretreatment involved a separation of the 0.45–63 μm fraction, mineralization with a mixture of hydrochloric and nitric acids (3:1 or 1:3) under atmospheric pressure in a fused silica vessel, followed by irradiation with ultraviolet light, after addition of hydrogen peroxide (to destroy organic matter). The most serious interference is from iron; this can be prevented by adding fluoride or pyrophosphate. The procedure is an alternative to the AAS determination of the total mercury content in sediments, especially with heavily polluted samples (mercury concentrations up to 0.01%).     

Extractive spectrophotometric determination of micro and sub-micro amounts of fluoride

A simple and sensitive extractive spectrophotometric determination of fluoride with the cerium(III)-alizarin complexan chelate has been investigated. The fluoro chelate formed is extracted into n-pentanol containing triethylamine. It is possible to achieve under selected conditions a selective extraction of the cerium(III)alizarin complexan-fluoride chelate. The stability of the chelate, the effect of temperature and the low absorbance of the blank are discussed. It is found that it is necessary to add a pH 9 buffer before the extraction. Procedures are given for the determination of 0.1-1 mug of fluoride in a 4-ml sample and 5-25 mug of fluoride in a 90-ml sample.     

Application of FT-Raman spectroscopy to quality control in brick clays firing process

This paper reports the study of the mineralogical evolution during the firing process (800-1150 degrees C) of the main types of raw materials used for the brick industry in Santa Cruz de Mudela (Ciudad Real, Spain). The mineralogical diversity observed in these materials leads to different behaviour during the shaping, drying and firing stages. Traditional use of similar working conditions in local industries, despite the mineralogical differences in the starting material, promotes the presence of defects in the drying and/or firing stages. This study attempt to implement some analytical guideline for the raw materials in order to improve the final product. Three types of raw materials obtained in different quarries have been characterised by means of chemical analysis with electron microprobe, powder X-ray diffraction and FT-Raman spectroscopy. The main difference between the clays studied is the carbonate content: one of the analysed samples is deficient in this component, while it is present as calcite (8%) or as calcite (14%) plus dolomite (10%) in the rest. The observed compositional differences seem to be relevant in the firing process. FT-Raman spectra reveal the onset of early vitrification (at about 900 degrees C) in the sample without carbonate. The importance of calcium and magnesium oxides, obtained from the corresponding carbonates, for the synthesis of new mineral phases that could slow down the vitrification process is discussed.     

An ab initio investigation into the SN2 reaction: Frontside attack versus backside attack in the reaction of F− with CH3F

The energy hypersurface for the attack of fluoride ion on methyl fluoride has been explored with ab initio LCAO-SCF calculations at a split-valence basis set level. Transition states for frontside and backside attack have been located. In addition to transition states, two possible F^–-CH₃F clusters have been identified. The transition state for the substitution of fluoride with retention of configuration is found to be 56 kcal/mol higher than the transition state for inversion of configuration. The transition state for hydride displacement with inversion is 62 kcal/mol above the transition state for fluoride substitution with inversion.     

Fluoride as a probe for H-bonding interactions in the active site of heme proteins: the case of Thermobifida fusca hemoglobin

The structural and functional properties of the active site of the bacterial hemoglobin from Thermobifida fusca are largely determined by three polar amino acids: TrpG8, TyrCD1, and TyrB10. We have exploited the availability of a combinatorial set of mutants, in each of which these three amino acids have been singly, doubly, or triply replaced by a Phe residue, to perform a detailed study on H-bonding interactions between the protein and heme-bound fluoride. By appropriate choice of the excitation conditions, ν(Fe-F) stretching bands have been detected in the resonance Raman spectra. In the wild-type protein and one of the mutants, two ν(Fe-F) bands have been observed and assigned to the presence of two protein conformers where fluoride is singly or doubly H-bonded. Furthermore, by plotting the CT1 charge-transfer transition energy vs the ν(Fe-F) wavenumbers, an empirical correlation has been found. The data are well fitted by a straight line with a positive slope. The position along the correlation line can be considered as a novel, general spectroscopic indicator of the extent of H-bonding in the active site of heme proteins. In agreement with the spectroscopic results, we have observed that the rate of ligand dissociation in stopped-flow kinetic measurements progressively increases upon substitution of the H-bonding amino acids. Molecular dynamics simulations have been performed on the fluoride complexes of native and mutated forms, indicating the prevalent interactions at the active site. All the techniques yield evidence that TrpG8 and TyrCD1 can form strong H bonds with fluoride, whereas TyrB10 plays only a minor role in the stabilization of the ligand.     

The determination of microgram quantities of fluoride : The use of the aluminium-haematoxylin complex

This paper describes a method for the spectrophotometric determination of fluoride. The fluoride is separated from interfering ions by the standard method of distillation as hydrofluosilicic acid. The fluoride in this distillate is determined by its destruction of the aluminium-haematoxylin complex; the amount of complex destroyed which is directly proportional to the concentration of fluoride is measured spectrophotometrically using radiation of 5700 A. The method will detect down to 0.05 p.p.m. of fluoride on a 10 gram sample with precision of rather better than ± 10% with larger amounts of fluoride. references p. 368.     

Application of high resolution-ICP-MS (sector field-ICP-MS) to the fast and sensitive quality control of process chemicals in semiconductor manufacturing

For fast routine analysis of process chemicals used in semiconductor technology such as tetramethylammonium hydroxide (TMAH), ammonium fluoride/hydrofluoric acid mixtures, phosphoric, sulphuric or peroxodisulphuric acid (PDSA) low blanks are the paramount requirement for reliable sector field ICP-MS ultratrace analysis. When solutions containing a high amount of dissolved solids e.g. seawater samples have been analysed before, a thorough cleaning procedure and an adapted element menu is essential to lower the instrument blanks where possible or to achieve sufficient limits of detection (LoD) even at high blank levels. Due to its improved transmission and its ability to resolve spectral interferences inductively coupled plasma-sector field mass spectrometry is capable of detecting 1 ng/g of all metal impurities even K, Ca, and Fe in every matrix used for semiconductor production. LoDs range from < 1 to 30 pg/mL in diluted chemicals corresponding to 5 to 800 pg/mL in the original. This work describes the experiences with instrument cleaning and maintenance, sample preparation and introduction. The interface region between torch and lenses was seen to be the main source of blanks for elements such as Na. All sample manipulation has to be carried out under clean room conditions. The use of an inert sample introduction system (ISIS), platinum cones and at least medium resolution for elements between 24 and 80 amu creates a very robust method. High efficiency sample introduction systems such as USN and MCN have been studied alternatively.     

Investigation of the conformation and electronic spectra of simple organic molecules by the NDDO method

Calculations have been performed by using the semi-empirical all-valence-electron NDDO method for the molecules ethylene, formaldehyde, formyl fluoride, carbonyl fluoride, butadiene, acrolein, glyoxal, acryloyl fluoride, acrylic acid, glyoxalic acid and oxalic acid. The conformational stability of the conjugated systems were correctly reproduced with the exception of acrolein and acryloyl fluoride. The calculated dipole moments are in good qualitative agreement with the experimental values. It has been found that the ionization potentials are higher by a factor of 1.35 than the experimental ones. The singlet—singlet and singlet—triplet transition energies and oscillator strengths of ethylene, formaldehyde and formyl fluoride are presented. A factor of 1.46 is needed for good agreement with the experimental transition energies.     

Indirect Spectrophotometric Determination of Fluoride In Water With Zirconium-Spadns By Flow Injection Analysis

Abstract

The zirconium-SPADNS method for the determination of fluoride based on the effect of fluoride ion on the color system (Zr-SPADNS), has been adapted to the continuous flow spectrophotometry. A manifold consisting of two lines was used. the decrease in the absorbance of Zr-SPADNS reagent at 590 nm is linear with fluoride concentration in the range 0.00-3.5 ppm. the method has a detection limit of 0.02 ppm fluoride. At a sampling rate of 50 determinations per hour, the precision was about 1% relative standard deviation. the method is applied to the determination of fluoride in natural water samples. the good agreement between the results obtained by this method and those obtained by a potentiometric method using a fluoride ion-selective electrode, show that the new method is potentially suitable for routine analysis. the effects of reaction conditions, flow parameters, and interferences on the FIA-spectrophotometric signals are reported. amount of interfering ion is present in quantity great enough to produce an error of 0.1 ppm or more, the sample must be distilled¹⁷     

Determination of Thorium and Total Rare Earths in Monazite Sand with Fluoride Electrode

A new method has been proposed to determine the total rare earths and thorium in monazite sand with fluoride electrode. The total amount of thorium and rare earths could be determined by back-titration with standard lanthanum solution in excess fluoride, and the rare earths were titrated directly with fluoride from separate sample. Fluoride electrode was used as indicator electrode. Precision and accuracy were improved by Gran's plot technique.