Thermal behavior of a pharmaceutical solid acetaminophen doped withp-aminophenol |
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Authors: | Damrongsak Faroongsarng Wichan Kadejinda Arunsri Sunthornpit |
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Institution: | (1) Department of Pharmaceutical Technology, Faculty of Pharmaceutical Sciences, Prince of Songkla University, 90112 Hat Yai, Thailand |
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Abstract: | Thermal behavior of a series of acetaminophen (APAP) doped withp-aminophenol (PANP) was studied by differential scanning calorimetry (DSC) to determine whether it exhibited a eutectic system.
Within the temperature range of 120 to 200° C, accurately weighed (1–2 mg) samples sealed in hermetic pans were calorimetrically
scanned with a low scanning rate of 1° C/min. The mixture formed a single eutectic with the composition ratio APAP/PANP of
0.6/0.4 at a temperature of 138° C, where it liquefied. Melting began as early as at the eutectic point, which was below the
melting temperature of APAP (169° C). The melting point as well as heat of APAP fusion was depressed with the increase in
doped PANP. It was postulated that there might be a deficit heat of APAP fusion in APAP doped with PANP, which was coincident
with the heat consumed by early liquefaction. The deficit heat was used to correct fraction molten in the van’t Hoff law of
purity determination. It was found that the purity determination of APAP doped with PANP was comparable to the UV-spectroscopic
method up to the maximum doped PANP level of 8 mol percent. It was concluded that DSC was able to approach early heat of liquefaction
of APAP doped with PANP. The van’t Hoff law may be applicable to the determination of APAP with the presence of PANP as a
eutectic impurity. |
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Keywords: | DSC Thermal Behavior the van’ t Hoff Law Purity Determination Acetaminophen p-Aminophenol Eutectic |
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