A simple, rapid, green and non-destructive F-19 time-domain NMR method for directly fluorine determination in powder of mineral supplements for cattle

摘要

A simple, rapid, green and non-destructive F-19 time-domain nuclear magnetic resonance (TD NMR) method for fluorine determination directly in the powder of cattle mineral supplements is presented. The measurements were performed in a 0.49 T (18.76 MHz for F-19) spectrometer using a 10 mm probe with 10 mu s dead time. Standard samples from 0 to 21,700 mg kg(-1)F were prepared diluting the appropriate amount of BaF2 in the salts Na2CO3: NaCl (1:1 w/w) that are normally used in the mineral supplements. The intensity of the free induction signal (FID), measured at 10 mu s after 90 degrees pulse and the fluorine content was used in an univariate model, with a limit of detection of 388 mg kg(-1) F. A partial least square model was also built using all FID data points and Fluorine content and yield a standard error of validation of 199 mg kg(-1)F. Accuracy was assessed by addition / recovery tests the analysis for two mineral supplements for cattle with trueness from 81 to 120%. Therefore, this is a green (non-chemical waste), simple (minimal sample preparation), fast (20 min) alternative method for determination of F in cattle mineral supplements.