Calorimetry a method to be used to characterise pyrolytically decarboxylated bicarbonate and assess its stability at elevated humidities

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• 作者：Ljunggren ; Lennart ; Volkova ; Natalia ; Hansson ; Henri
• 关键词：Calorimetry ; Sodium bicarbonate ; Sodium carbonate ; Relative humidity ; Enthalpy ; Pyrolytic decarboxylation
• 刊名：International Journal of Pharmaceutics
• 出版年：2000
• 出版时间：July 20, 2000
• 年：2000
• 卷：202
• 期：1-2
• 页码：71-77
• 全文大小：1.65 M

文摘

Microcalorimetry was used to characterise bicarbonate after treatment at high temperatures. By measuring the heat flow from a sample of bicarbonate at 100 % relative humidity, the net exothermic contribution could be used to estimate the fraction of pyrolytically formed Na<sub>2sub>CO<sub>3sub>. The enthalpy value corresponding to the heat of solution of Na<sub>2sub>CO<sub>3sub> was also applicable to a physical mixture of NaHCO<sub>3sub>/Na<sub>2sub>CO<sub>3sub>. However, from the characteristic peaks of the heat flow versus time curve, pyrolytically formed Na<sub>2sub>CO<sub>3sub> could be distinguished from that present in the physical mixture. The different bicarbonate batches of varying degree of pyrolytic decarboxylation were also observed at an elevated relative humidity of 54 % . From these measurements it could be inferred that a decarboxylation of up to 4.5 % could be allowed without any significant effect on the stability of bicarbonate at 54 % .