A Novel Thermal Infrared Enthalpimetric Method for Fast, High-Throughput Determination of the Content Uniformity of Captopril Tablets

Content uniformity (CU) is a parameter used to ensure the uniformity of the amount of active substances in pharmaceutical preparations. It is often evaluated in the quality control of pharmaceutical dosage forms, and a novel method was proposed for CU determination using thermal infrared enthalpimetry (TIE). Captopril tablets were dissolved in 24-well microplates and the heat released from the reaction of captopril and I2 was monitored with an infrared camera. Some experimental parameters were adjusted, as captopril/I2 ratio, stirring speed and dispensing rate, and the most suitable conditions were 1.00:1.00 (v/v), 250 rpm and 0.57 mL s-1, respectively. Interferences from tablet adjuvants (e.g., starch, cellulose and lactose) were not observed. The results obtained by TIE did not differ statistically (Student’s t-test, p > 0.05) from those from official method (UV spectrophotometry) described in pharmacopeia. The TIE method required 31 and 12 times less reagent and time, respectively. Therefore, the proposed method was suitable for routine analysis and agrees with the requirements of green analytical chemistry.