Novel solid-state compounds of heavy rare-earth (III) picolinates. A pyrolytic study using: TG-DSC-IR, HSM-MS and GC-MS

Abstract

Heavy trivalent lanthanides and yttrium picolinates were synthesized by complexation of basic rare-earth metal carbonates with an aqueous solution of picolinic acid. The novel compounds were obtained with the general formula Ln(L)3•nH2O, where L is picolinate and n= 1.5 H2O (Dy, Ho, Yb, Lu and Y), 2 H2O (Tb and Tm) and 2.5 H2O (Er). The stoichiometry of the complexes was calculated through mass losses found using thermogravimetry (TG), complexometry and elemental analysis (EA). The thermal behavior in oxidative and pyrolytic atmospheres of the compounds was analyzed by simultaneous thermogravimetry -differential scanning calorimetry (TG-DSC). The gaseous products of the pyrolysis were determined throughout by monitoring the evolved species using TG-DSC, Fourier transform infrared spectroscopy (TG-DSC-FTIR), hot-stage microscopy mass spectrometry (HSM-MS), and gas chromatography-mass spectrometry (GC-MS). The obtained results validated mass loss assignments made using the TG curves. However, gaseous product analysis indicates the degradation processes are more complex than the thermoanalytical techniques suggest alone. This study used a GC-MS technique to identify the condensed gaseous products obtained during the second step of the thermal degradation of the picolinate complexes. The analysis of the symmetric and asymmetric stretching frequencies of the carboxylate group in the FTIR spectra showed a monodentate bonding mode. The compounds were obtained in the amorphous state, as indicated by the powder X-ray diffractometry (PXRD) data.

In Silico Study, Physicochemical, and In Vitro Lipase Inhibitory Activity of α,β-Amyrenone Inclusion Complexes with Cyclodextrins

“…Thermogravimetric (TGA) analysis is a technique in which the mass of the sample is continuously measured as a function of temperature, that is, as it is heated or cooled [ 53 ].…”

Physicochemical characterization of a lycopene-loaded mesoporous silica nanoparticle formulation

“…In parallel, the precipitate was analyzed by Thermogravimetric analysis (TGA) in a TG-DSC 1 (Mettler Toledo) with purge gas of dry air atmosphere at a flow of 50 mL/min, heating rate of 10°C/min and temperature range of 30-800°C. The samples weighed about 3 mg and an open alumina crucibles were used for this experiment [44]. Normalization of the samples was performed to provide a direct comparison of thermal curves.…”

“…Verification of the method's ability to resist small but deliberate variations using the accuracy criteria of 50 mL min −1 , heating rate of 10 • C min −1 and temperature range of 30-800 • C. The samples weighed about 3 mg and an open alumina crucibles were used for this experiment. [44] Normalization of the samples was performed to provide a direct comparison of thermal curves.…”

HPLC and thermal analysis, do they have a good correlation to quantify lycopene in mesoporous silica nanoparticles?

“…Purge gas of dry air atmosphere at a ow of 50 mL min − 1 , heating rate of 10°C min − 1 and temperature range of 30-800°C. The range Samples weighed about 3 mg and open alumina crucibles were used (Nascimento et al 2019).…”