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 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.     

Molecular absorption spectrometry (MAS) by electrothermal evaporation in a graphite furnace-XIII Determination of traces of fluoride by mas of AlF after liquid-liquid extraction of fluoride with triphenylantimony(V) dihydroxide

The determination of traces of fluoride by means of the molecular absorption of AlF volatilized in graphite cuvettes is described. An extraction method for separation and preconcentration of the fluoride has been developed, to avoid matrix effects. The fluoride is extracted with 10(-3)M triphenylantimony(V) dihydroxide in M1BK, and stripped with 0.025M barium hydroxide. The method is sensitive and specific for fluoride. The detection limit is about 0.3 ng of fluoride, and the fluoride content of 6 ml of 10(-7)M solution can be determined. The determination is possible in presence of various ions, but it is estimated that usage of trace matrix separation leads to a considerable improvement in the relative detection limits (by 2-3 orders of magnitude), levels as low as 0.01 ppm being detectable in some matrices.     

Determination of the fluoride distribution in rabbit bone using instrumental neutron activation analysis

An instrumental neutron activation analysis (INAA) technique, based on the¹⁹F(n,)²⁰F reaction, has been development for the determination of fluoride in bone. The purpose was to study fluoride distribution in different kinds of bone samples using a rabbit model. The rationale for the study stems from the posible correlation between fluoride in bone and osteoporosis. The sodium concentration in the bone was used to correct the²⁰F peak area for the²³F(n,)²⁰F contribution. Two secondary standards, teflon tape and teflon coated dacron line, were used to quantify fluoride concentration. They proved to be stable and consistent with respect to their fluoride concentration. Bone specimens from 10 sites and two tooth samples were analyzed for fluoride. Fluoride concentration ranged from 305 ppm in the tibia long bone to 585 ppm in the humerus trochanter end and the magnitude of fluoride concentration levels is age depdentent. The detection limit of the fluoride is approximately 5 ppm using a 100 mg bone sample.     

Determination of Silicate By Nonsuppressed Ion Chromatography

Abstract

In previous papers the authors reported that nonsuppressed ion chromatography using potassium hydroxide solution as an eluent was a very sensitive and effective method for the analysis of anions and that this method could be applied to the determination of anions in environmental water samples.

In this paper, this method was applied to the determination of silicate without the interference of fluoride ion when using 0.5mM potassium hydroxide solution, Moreover, this method was compared with silicomolybdate methods and good agreement was obtained between these two methods.

The percent standard deviation was 5.5% when determining lppm of silicate and the calibration curve was linear at concentrations less than 2.5ppm. The detection limit was less than 50ppb.     

Potentiometric determination of iron using a fluoride ion-selective electrode-the application of the Apple II-ISE intelligent ion analyzer

A new method for determining iron is based on both nonlinear regression calibration plots and parabolic interpolation using a fluoride ion-selective electrode (ISE) and the Apple II-ISE intelligent ion Analyzer developed by ourselves. The experimental conditions for determining iron are discussed. The appropriate acidity of the experimental solution is pH 3, controlled by total ionic strength adjustment buffer (TISAB) that is composed of glycine (aminoacetic acid), nitric acid and sodium nitrate. The suitable total concentration of fluoride is equal to the highest concentration of iron in the standard series. Because the mathematical model of the method coincides with the experimental data the Apple II-ISE intelligent ion Analyzer can perform data acquisition and data processing, and the performance of fluoride electrode is excellent, the new method for determination of iron is fast and accurate. This method has been used successfully in the determination of iron in mineral samples.     

Studies on pollutants: A new reagent for the detection of fluoride

A new solid analytical reagent is reported for the detection and semiquantitative determination of traces of fluoride. A blue (λ_max 590 nm) trypan blue dye is liberated from an insoluble zirconium-trypan blue complex by the action of fluoride in dilute acetic acid medium. The detection limit is 0.8 ppm and the range of semiquantitative determination is 0.8 to 8 ppm. The method is simple and can be conveniently used for field detection of fluoride in polluted waters.     

A study of the cerium-alizarin complexan-fluoride reaction

The optimum pH range of the cerium^III-alizarin complexanate method for fluoride has been established as pH 5.0–5.2 at which value the method may be applied over a wide concentration range from 5 μg of fluoride ion (0.1 ppm) to 1.6 mg (>160 ppm) using a conventional spectrophotometer. The nature of the changes produced in the colour system by variation of pH are briefly discussed and the interference of 23 selected cations and 3 common anions has been examined. Practically all of the serious cationic interference can be overcome by the simple addition of a masking agent but, in a few cases, a preliminary extraction with 8-hydroxyquinoline and chloroform is required.     

Fluoride determination by magnesium atomic absorption inhibition—release effects

The pH characteristics of fluoride inhibited magnesium atomic absorption signals distinguish them from other anions commonly present. The new technique involves addition of magnesium chloride and then acid to the sample solution while monitoring the magnesium atomic absorption signal. The signal enhancement due to the pH effect is proportional to flouride concentration. A sensitivity of 0.10 absorbance units/ppm F and a determination limit of 0.3 ppm F were found. Tap water fluoride determination results compare well with those for established methods. Various data point to a mechanism involving simple displacement of flouride in the refractory compound to form hydrogen fluoride.     

Spectrofluorimetric determination of submicrogram amounts of aluminium using salicylidene-o-aminophenol

Salicylidene-o-aminophenol provides a sensitive spectrofluorimetric reagent for the determination of aluminium down to 27 ng (or 2.7 x 10(-4) ppm in the final solution). The most suitable conditions of pH (5.6), reagent concentration and development time (>20 min) have been established. Extraction with sodium diethyldithiocarbamate into ethyl acetate at the pH of the determination renders the method highly selective; out of 46 foreign cations examined only chromium(III), scandium and thorium interfere. Anions which form complexes with aluminium, such as citrate, tartrate and fluoride, also cause interference, but none of the common anions interferes. A 1:1 stoichiometry of the complex has been established and some conclusions have been drawn concerning its nature.     

Stopped-flow kinetic determination of aluminum in Chinese tea leaves by fluoride ion-selective electrode potentiometry

A stopped-flow kinetic potentiometric method for the determination of aluminum is described, based on monitoring the reaction between aluminum and fluoride at pH 3.0 using fluoride ion-selective electrode. The initial rate of the reaction is proportional to the concentration of aluminum present in the solution. The method is simple and rapid and has been applied to the determination of aluminum in Chinese tea leaves after microwave digestion.     

Spectrographic analysis of high purity manganese dioxide

The fluoride content of aqueous and organic Purex process solutions can be determined with good reproducibility and accuracy. The method includes a distillation separation of fluoride and its subsequent electrometric determination using a fluoride-selective electrode. The analytical range covers 5 to 500 μg of fluoride per aliquot and the concentration limit is 5×10^?5 M (1 ppm). Complexing cations like Al(III), Zr(IV), La(III), and U(VI) do not interfere.     

Optical-fibre sensing of fluoride ions in a flow-stream

The Alizarin Fluorine Blue method for the determination of fluoride has been adapted for use with optical fibres. The reagent was immobilized on a polymer matrix, Amberlite XAD-2, and the reflectance of this reagent phase was measured as a function of fluoride concentration by use of a flow-cell assembly and a bifurcated fibre-optic system. A linear response was obtained for 0.16-0.95mM fluoride at a pH of 4.1, with a response time of approximately 12 min.     

Separation of fluoride ion by extraction with triphenyltin chloride. Application for NAA of fluorine by means of 14-MeV neutrons

The separation of fluoride by extraction with toluene solution of triphenyltin chloride has been studied. Quantitative isolation of fluoride from solutions with a wide acidity range (pH 4.0–11.5) has been established. It is suggested that interferences by Ca, Mg, Fe, and Al can be avoided by masking these elements using sulfate and hydroxyde ions. Interference by phosphate ions can be overcome in a similar fashion. The halogenated species can be masked by mercury nitrate. Detection limit for fluorine determination is about 3 g for a neutron generator flux of 2·11¹¹ n·cm^–1·s^–1. A method for fluorine assay in water using a neutron generator with a detection limit of 1 ppm has been developed.     

Solid phase extraction-spectrophotometric determination of fluoride in water samples using magnetic iron oxide nanoparticles

A new, sensitive, fast and simple method using magnetic iron oxide nanoparticles (MIONs), as an adsorbent has been developed for extraction, preconcentration and determination of traces of fluoride ions. The determination method is based on the discoloration of Fe(III)-SCN complex with extracted fluoride ions which was subsequently monitored spectrophotometrically at λ_max = 458 nm. Various parameters affecting the adsorption of fluoride by the MIONs have been investigated, such as pH of the solution, type, volume and concentration of desorbing reagent, amount of adsorbent and interference effects. A linear response for the determination of fluoride was achieved in the concentration range of 0.040-1.250 μg mL⁻¹. The limit of detection (LOD) and limit of quantification (LOQ) for fluoride based on 3 times and 10 times the standard deviation of the blank (3S_b, 10S_b) were 0.015 and 0.042 μg mL⁻¹ (n = 20) for fluoride ion, respectively. A preconcentration factor of 50 was achieved in this method. The proposed procedure has been applied for determination of fluoride concentration in various water samples. The results obtained from this method were successfully compared with those provided by standard SPADNS method.     

Colorimetric determination of fluoride ion with a solid analytical reagent

A colorimetric procedure is proposed for the estimation of fluoride ions in μg range in aqueous samples. The method involves the use of a solid analytical reagent and exhibits an operational simplicity. The detection limit of 1 ppm in an aqueous sample is conveniently achieved in the direct application. The interfering ions are initially removed in an ion exchange step, which also serves as a concentration step for fluoride if present in low concentration.     

Rapid method for the determination of trace fluoride and activation of ion-selective electrode.

A method for activating ISE is proposed that can allow determination of the fluoride concentration at ng mL(-1) level with good precision and accuracy. Fluoride ISE is activated in 0.5 mol L(-1) HClO4 medium and then fluoride is determined in the same medium. The linear range for the determination of fluoride is between 1.00 x 10(-2)-1.00 x 10(-7) mol L(-1), and the detection limit of the method is 1.0 ng mL(-1). The advantage of this method is that it is free from the use of TISAB solution while being, time-saving and labor-saving. A mechanism study of the activation of FISE in HClO4 medium is explained. The method has been used for the determination of trace fluoride in milk and flour with satisfactory results.     

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.     

Spectrophotometric determination of Zineb (a dithiocarbamate fungicide) by the methylene blue method

Summary A spectrophotometric method has been developed for the determination of Zineb in water and vegetables. The method is based on the liberation of hydrogen sulphide from Zineb, which is trapped in an absorbing solution of triethanolamine, sodium hydroxide and ethylenediamine tetraacetic acid. The absorbing solution is treated with N-N-dimethyl-p-phenylene diamine sulphonate and ferric chloride to form methylene blue. Beer's law is obeyed over the concentration range of 3–32 ppm. The method is simple and can be used for the determination of Zineb in the presence of other dithiocarbamates.     

Determination of fluoride by radiometric assay of181Hf back-extracted from HTTA in benzene

Determination of fluoride at trace level is important for the specification analysis of nuclear fuel samples. This is generally accomplished by pyrohydrolytic separation followed by ion selective electrode potentiometry. In the present work, a method has been developed for the determination of fluoride by radiometric assay of¹⁸¹Hf back-extracted from thenoyltrifluoracetone (HTTA) in benzene.¹⁸¹Hf back-extracted is proportional to the concentration of fluoride.