Thermal stability of vitamin C: Thermogravimetric analysis and use of total ion monitoring chromatograms

• Published in: Journal of pharmaceutical and biomedical analysis 2012-02, Vol.59, p.190-193
• Main Authors: Juhász, Márta, Kitahara, Yuki, Takahashi, Seiji, Fujii, Toshihiro
• Format: Article
• Language: English
• Subjects: activation energy; air; Analysis; Analytical, structural and metabolic biochemistry; Arrhenius parameters; ascorbic acid; Ascorbic Acid - analysis; Ascorbic Acid - standards; Biological and medical sciences; Decomposition kinetic; Drug Stability; Drug Storage; EGA–Li +IAMS; Fundamental and applied biological sciences. Psychology; General pharmacology; Hot Temperature; Kinetics; l-ascorbic acid; mass spectrometry; Mass Spectrometry - methods; Medical sciences; monitoring; nitrogen; Pharmacology. Drug treatments; Shelf life; TGA; thermal degradation; thermal stability; Thermogravimetry; weight loss
• ISSN: 0731-7085; 1873-264X
• DOI: 10.1016/j.jpba.2011.10.011

► Thermal decomposition kinetics and shelf life of vitamin C were studied. ► TGA and EGA–Li +IAMS systems were used with non-isothermal heating. ► Vitamin C was shown to have higher thermal stability in nitrogen than in air. ► The shelf lives ( t 90%,25 °C ) estimated by TGA agreed with the values estimated by using a pyrogram. ► EGA–Li +IAMS is a reliable alternative method to TGA for thermal stability studies. The thermal decomposition kinetics and shelf life of vitamin C in nitrogen or air were studied by using thermogravimetric analysis (TGA) and evolved-gas analysis–lithium-ion attachment mass spectrometry (EGA–Li +IAMS). Arrhenius parameters obtained via TGA were reported for thermal decomposition. For vitamin C in a nitrogen atmosphere, the activation energy ( E a ) was 25.1 kcal/mol and the pre-exponential factor ( A) was 2.5 × 10 11 min −1. The kinetic parameters estimated via TGA agreed with values estimated from a pyrogram when the weight loss observed by TGA was shown to be due to gas evolution as a result of decomposition of the compound. Thermal stability was expressed by calculating the time for 10% of the vitamin C to decompose at 25 °C ( t 90%,25 °C ). The t 90%,25 °C for vitamin C obtained via TGA or EGA–Li +IAMS was higher in nitrogen (2.0 and 2.0 years, respectively) than in air (1.3 and 1.6 years, respectively). This indicates that the type of atmosphere influences vitamin C stability.