Dx 120 ion chromatography

Enamel dissected from each tooth was ground into a powder in an agate mortar, then weighed and mineralized, using HNO₃ and H₂O₂ (Merck, Darmstadt, Germany) at 80 °C for 3 h. All the solutions were prepared in deionized water with a resistivity of <18 m MΩ.cm (at 25 °C) using the Milli-Q system (Millipore, Molsheim, France). The standard fluoride (F⁻) solution was prepared by diluting a solution of 1000 mg F⁻/L (Merck). The mobile phases were prepared from appropriate aliquots of the following salts: Na₂CO₃, and NaHCO₃ (POCh, Gliwice, Poland). The F⁻ anions were separated by DX-120 ion chromatography (Dionex, Sunnyvale, CA, USA) with conductivity detection. The eluent was a mixture of Na₂CO₃/NaHCO₃, administered in isocratic mode at a 1 mL/min flow rate. The fluoride content was determined from the standard curve and converted into milligram units per enamel gram.

The crude polysaccharide component of C. fistula (2.0 mg) was treated with 4 mL of 2 M H₂SO₄ at 105 °C for 150 minutes. The resulting liquid was diluted to a volume of 10 mL. A chromatographic technique was done using Dx-120 ion chromatography (Dionex, Sunnyvale, CA, USA) according to the method described by ref. 17 .