Fluoride, determination extraction

Sill et al. [26] have discussed a spectrometric method for the determination of americium and other alpha-emitting nuclides, including curium and californium, in potassium fluoride-pyrosulfate extracts of soils. Sekine [27] used a-spectrometry to determine americium in soils with a chemical recovery of 60-70%. Joshi [28] and Livens et al. [29] have discussed methods for the determination of241 americium in soils. 

Fluoride Determine as directed under Fluoride Limit Test, Appendix IIIB, using 1.0 g of sample, accurately weighed. Lead Determine as directed in the APDC Extraction Method under Lead Limit Test, Appendix IIIB. 

Assay Dissolve 250 mg of sample, accurately weighed, in 100 mL of water and 4 mL of 2.7 N hydrochloric acid, boil to effect solution, and cool. While stirring, preferably with a magnetic stirrer, add about 30 mL of 0.05 M disodium EDTA from a 50-mL buret, then add 25 mL of 1 N sodium hydroxide and 300 mg of hydroxy naphthol blue indicator, and continue the titration to a blue endpoint. Each milliliter of 0.05 M disodium EDTA is equivalent to 6.807 mg of CaS04. Fluoride Determine as directed under Fluoride Limit Test, Appendix IIIB, using 1.67 g of sample, accurately weighed. Lead Determine as directed in the APDC Extraction Method under Lead Limit Test, Appendix IIIB. 

Sodium fusion. About 0-3 g. of material in a gelatine capsule was placed in a Parr bomb, together with 0-2 g. of metallic sodium, all the operations being carried out in a dry-box. The bomb was heated for 1 hr. over a Meker burner, cooled, and opened at room temperature, and the excess of sodium was destroyed by boiling with absolute alcohol. Sodium fluoride was extracted from the residue with water and the fluorine determined as lead chloride fluoride (Found F, 32-7%). 

F can also be separated by solvent extraction. Faure et al. (223)(224) used solvent extraction with disphenyldichiorosilane in isopropyl ether for the determination of oxygen in molybdenum and lead. The separation of F by solvent extraction using triphenyl antimony (V) derivatives is described by Chermette et al. (225)(226). It is shown that, if fluoride is extracted with an excess of reagent, the extracted salt is triphenyl-antimonyhydroxyfluoride if the pH is not too low. The partition constants of this compound in benzene-water and carbon tetrachloride-water systems are high. The kinetics of the fluoride exchange reaction ... 

Oxygen and nitrogen also are deterrnined by conductivity or chromatographic techniques following a hot vacuum extraction or inert-gas fusion of hafnium with a noble metal (25,26). Nitrogen also may be deterrnined by the Kjeldahl technique (19). Phosphoms is determined by phosphine evolution and flame-emission detection. Chloride is determined indirecdy by atomic absorption or x-ray spectroscopy, or at higher levels by a selective-ion electrode. Fluoride can be determined similarly (27,28). Uranium and U-235 have been determined by inductively coupled plasma mass spectroscopy (29). 

Pretreatment of the collected particulate matter may be required for chemical analysis. Pretreatment generally involves extraction of the particulate matter into a liquid. The solution may be further treated to transform the material into a form suitable for analysis. Trace metals may be determined by atomic absorption spectroscopy (AA), emission spectroscopy, polarogra-phy, and anodic stripping voltammetry. Analysis of anions is possible by colorimetric techniques and ion chromatography. Sulfate (S04 ), sulfite (SO-, ), nitrate (NO3 ), chloride Cl ), and fluoride (F ) may be determined by ion chromatography (15). 

Note. Under the above conditions of determination the following elements interfere in the amount specified when the amount of Mo is 10 fig (error greater than 3 per cent) V, 0.4 mg, yellow colour [interference prevented by washing extract with tin(II) chloride solution] Cr(VI), 2 mg, purple colour W( VI), 0.15 mg, yellow colour Co, 12 mg, slight green colour Cu, 5 mg Pb, 10 mg Ti(III), 30 mg (in presence of sodium fluoride). 

Insoluble fluorosilicates are brought into solution by fusion with four times the bulk of fusion mixture, and extracting the melt with water. In either case, the solution is treated with a considerable excess of ammonium carbonate, warmed to 40 °C, and, after standing for 12 hours, the precipitated silicic acid is filtered off, and washed with 2 per cent ammonium carbonate solution. The filtrate contains a little silicic acid, which may be removed by shaking with a little freshly precipitated cadmium oxide. The fluoride in the filtrate is determined as described in Section 11.59. 

Ke and Regier [71] have described a direct potentiometric determination of fluoride in seawater after extraction with 8-hydroxyquinoline. This procedure was applied to samples of seawater, fluoridated tap-water, well-water, and effluent from a phosphate reduction plant. Interfering metals, e.g., calcium, magnesium, iron, and aluminium were removed by extraction into a solution of 8-hydroxyquinoline in 2-butoxyethanol-chloroform after addition of glycine-sodium hydroxide buffer solution (pH 10.5 to 10.8). A buffer solution (sodium nitrate-l,2-diamino-cyclohexane-N,N,N. AT-tetra-acetic acid-acetic acid pH 5.5) was then added to adjust the total ionic strength and the fluoride ions were determined by means of a solid membrane fluoride-selective electrode (Orion, model 94-09). Results were in close agreement with and more reproducible than those obtained after distillation [72]. Omission of the extraction led to lower results. Four determinations can be made in one hour. 

Holm et al. [74] used a spectrometry for the determination of 237neptunium in seawater. The actinides are preconcentrated from a large seawater sample by hydroxide precipitation. The neptunium was isolated by ion exchange, fluoride precipitation, and extraction with TTA. 238Neptunium or 235neptunium was used to determine the radiochemical yield. 

The efficiency of the extraction depends on the coordinating ability of the solvent, and on the acidity of the aqueous solution which determines the concentration of the metal complex. Coordinating ability follows the sequence ketones > esters > alcohols > ethers. Many metals can be extracted as fluoride, chloride, bromide, iodide or thiocyanate complexes. Table 4.5 shows how the extraction of some metals as their chloro complexes into diethyl ether varies with acid concentration. By controlling... 

When substances adsorbed on aerosol particles are to be determined, the gas is passed through a membrane or other filter and the filter is dissolved in or extracted with a suitable solution. An interesting method is used for determination of fluoride adsorbed on atmospheric aerosols [87]. The particles are trapped on a filter impregnated with citric acid and heated to 80 °C, while the fluorides pass through and are absorbed in a thin layer of sodium carbonate in a spiral absorber. The sodium carbonate is periodically washed with a sodium citrate solution, in which solution the fluoride is then determined, and the absorption layer regenerated. 

The sensitivity of determination of traces of F can be increased by extraction with tetraphenylantimony(V)dichloride in CCI4 in the presence of CDTA and phosphate buffer. After back-extraction into an aqueous solution, the extractant is removed by shaking with CCI4. This concentrated solution is analyzed using a fluoride ISE and down to 10 m F can be determined in the original solution [55h]. For determination of F" after electrochemical generation of fluoride, see [88]. 

Total decomposition of the sample, the purpose of which is to release fluorine from inorganic or organic matrixes and convert it to fluoride ions, is usually a prerequisite for determining the amount of total fluorine. Commonly used procedures involve oxygen bomb combustion in a closed bomb [176,180], open ashing [181,182], alkali hydroxide or alkali carbonate fusion [151,183-187], pyrohydroly-sis [187-191], acid extraction [192,193] and microwave acid digestion [194-196]. 

Determination of total fluoride in soil, sediments, oxides and other raw materials requires complete decomposition of the sample. Accumulation of fluoride in soil can be studied by employing appropriate extraction procedures. 

Total fluorine in fluoride supplements and dental products could be determined with minimal samples pre-treatment as for example by direct acid extraction or heating in TISAB buffer solution and subsequent determination of fluoride using fluoride ISE for the reason that entire fluorine, in these products, should be, by definition, available as free inorganic fluoride. 

J.L. Manzoori, A. Miyazaki, Indirect inductively coupled plasma atomic emission determination of fluoride in water samples by flow injection solvent extraction. Anal. Chem. 62 (1990) 2457-2460. 

A method has been described [ 1 ] for the determination of borate in soils based on the conversion of borate in a hot water extract to fluoroborate by the action of orthophosphoric acid and sodium fluoride. The concentration of fluoroborate is measured spectrophotometrically as the blue complex formed with methylene blue which is extracted into 1,2-dichloroethane. Nitrates and nitrites interfere, but these can be removed by reduction with zinc powder and orthophosphoric acid. 

Vickery and Vickery [9] have investigated the interference by aluminium and iron in the ion-selective electrode method for the determination of fluoride in plant extracts. They demonstrated that plant ashes may contain sufficient of these two elements to seriously interfere in the determination of fluoride when using the fluoride-selective electrode. In the presence of these metals, the known additions method gives erroneous results, as did that involving the attempted formation of complexes with ethylene diamine tetraacetic acid (disodium salt) or 1,2-cyclohexylenedinitrilotetraacetic acid. 

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