Sulfathiazoles are sulfonamides with antibiotic effect that occur in various polymorphous forms and that are often used in veterinary medicine. This Application Note shows the differentiation between commercial and sulfathiazole form I using near-infrared spectroscopy (NIRS) with the help of the overtone frequencies of N-H stretching vibration. Form I is the least stable polymorphous form. Crystallization and polymorphism must be monitored as part of quality controls. In this, NIRS is considerably more rapid and more reliable than conventional laboratory methods.


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