Determination of calcium in tablets containing calcium citrate using thermogravimetry (TG)

Abstract

The present study utilized thermogravimetry (TG) and optical emission spectroscopy with inductively coupled plasma (ICP/OES) to determine the amount of calcium in calcium citrate tablets, which are used for the treatment of osteoporosis. The samples were characterized using Fourier transform infrared spectroscopy (FTIR), termogravimetry/derivative thermogravimetry (TG/DTG), differential thermal analysis (DTA), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). In the DTA and DSC curves obtained, both endo- and exothermic events were observed, which are indicative of dehydration and decomposition, respectively. The X-ray diffractograms showed that the samples present crystallinity. Additionally, peaks observed in the X-ray diffractograms indicate the presence of a calcium hydroxide residue due to the reaction between calcium oxide with moisture in the air. The calcium content obtained by TG from the tablet sample (17.77%) was similar to that obtained using ICP-OES (16.84%).