Fluorine determination in biological tissues and its impact oxidative biomarkers.

This study proposes a strategy for the determination of total fluorine in biological tissues using microwave-induced combustion (MIC) for sample preparation, followed by determination by ion chromatography (IC), after evaluating different drying strategies. An ion-selective electrode (ISE) was also used to compare the results. The method was applied to liver, kidney, and brain samples from Winstar rats exposed to increasing concentrations of fluorine in drinking water. MIC parameters were evaluated through independent recovery tests, with the use of 150 mmol L-1 (NH4)2CO3 as an absorbent solution and 500 mg of sample representing the suitable MIC conditions. To assess the accuracy of the proposed method, a certified reference material (CRM), NIST 1566a (oyster tissue), was used. The recovery assay was also performed using 150 mg of CRM as an additive, mixed with 250 mg of one of the treated liver samples (total of 400 mg). A recovery of 102 ± 4% was obtained, proving the efficiency of the proposed method for the determination of fluorine in the liver of animals. Regarding the limits of detection by IC, values of 2.5, 4.0 and 9.0 mg kg-1 were obtained for liver, kidney and brain samples, respectively. Based on the obtained results, it was possible to identify a higher concentration of fluorine in the treated group compared to the control group for the liver and kidneys, but not for the brain, since the brain samples were all below LOQ. Exposure to fluoride at 20 mg L-1 caused a significant increase in reactive oxygen species (ROS) and alterations in antioxidant enzymes in the liver, with decreased catalase activity and increased superoxide dismutase activity. No such significant alterations were observed in the kidneys. Finally, the proposed method (MIC + IC) was suitable for the determination of total fluorine in complex biological matrices, and it contributes to the expansion of the currently limited database on fluorine levels in biological tissues.