CONICET | Buscador de Institutos y Recursos Humanos

MEASUREMENT OF IONIC (F), ACID-LABILE (FAL) AND ACID-RESISTANT (FAR) FLUORINE Pera L, Gervasoni M, Rigalli A, Puche RC. Lab Biol Ósea. Fac. Cs. Medicas UNR. Potentiometry of F is only possible in aqueous samples at levels greater than 0.5 mM. After a dose of monofluorophosphate (MFP) there are non ionic fluorine, undetectable with the fluoride selective electrode (FSE). Total fluorine (FT) of a sample is the sum of F-, FAL and FAR. Both FAL and FAR are not directly detected with FSE. FAL distilles as F from compounds by treatment with strong acids, and FAR distilles as F after incineration and treatment with strong acids. The aim of this work was to develop a technique to measure potentiometrically F, FAL and FAR. F measurement (F): with the FSE directly on the sample with the addition of 10 % V/V of buffer pH 5.5 to adjust ionic strength and to complex trivalent metals. Measurement of F post-isothermic distillation (mDI): 100 ml of sample are mixed with 100 ml H2SO4 in a 1.5-ml tube with a microtube containing NaOH, cupped and maintained at 37° C for 6 days. F and FAL distillates from the sample to the alkali solution, where F is measured with the FSE. FT measurement post-incineration and isothermic distillation (FT): 100 ml of sample are absorbed on CaSO4, incinerated at 500° C for 6 hs, and subjected to uDI. Calculations: FAL=mDI- F, FAR= FT-FAL. Calibration curves with aqueous NaF were performed. Nernst equation fitted significantly for the different forms of fluorine (p< 0.05). F: r= 0.98, mDI: r= 0.94 and FT: r= 0.91. As an example, this methodology was applied to bone from rats treated with MFP, F=237±25, FAL=64±11 and FAR=770±37 nmoles. Conclusion: This methodology allows measurement of fluorine not detected directly with the electrode in biological samples.

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