DSC Measurement Method for Sulfapyridine
Sulfapyridine is a sulfonamide antibiotic with a molecular weight of 249.29, molecular formula C₁₁H₁₁N₃O₂S, and CAS No. 144-83-2.It appears as a white to off-white solid at room temperature, stable in properties, flammable, and light-sensitive.It is slightly soluble in water, soluble in a little DMSO and a little methanol.
Experimental Purpose
Differential Scanning Calorimetry (DSC) is widely used to study the thermal behavior and physicochemical properties of drugs, and plays an important role in pharmaceutical R&D and quality control.
For sulfapyridine, a sulfonamide antibacterial drug:
DSC can be used to determine its purity. The melting point of pure sulfapyridine is 191–193 °C. DSC accurately measures its melting peak, which indirectly reflects sample purity.
Sulfonamides often exhibit polymorphism. Different crystal forms show different thermodynamic stability, solubility, and bioavailability. DSC can identify and distinguish crystal form transitions.
It can also be used for drug-excipient compatibility studies by monitoring the thermal behavior of sulfapyridine mixed with excipients to detect possible interactions.
Experimental Apparatus
① ST146 Crystalline Thermal Analyzer
② Sampler, crucible, desiccator, high-precision balance and other auxiliary equipment
Experimental Procedures
①Inspect the instrument and auxiliary equipment to ensure they are clean, dry, and free of contamination.
②Calibrate the instrument for temperature, heat flow, and specific heat capacity using standard materials such as indium, zinc, and sapphire.
③Dry the sample. Weigh a sample mass of typically 5 ± 2 mg, then seal it in a dedicated crucible.
④After calibration, set parameters according to measurement requirements. The instrument will automatically measure and display results.
⑤Repeat the test 1–3 times.
Experimental Results and Analysis
In the standard heating program (10 K/min, 30–400 °C):
The measured melting enthalpy (ΔH) of the sample was approximately 145 J/g.
Melting occurred at about 190 °C.
Crystallization was observed during cooling at approximately 140–160 °C.
Melting occurred again at about 190 °C in the second heating, consistent with the initial melting point.
Decomposition was observed at 250 °C.
Based on comprehensive evaluation, the sample complies with pharmacopoeia requirements: it is pure and well-preserved.