Determination of primary aromatic amine in quality control of X-ray contrast media by flow-injection analysis

An automated flow-injection method for determination of primary aromatic amines based on the Bratton-Marshall reaction is described. This method is used for analysis quality control of three different X-ray contrast media (Omnipaque, Imagopaque and Visipaque) which are viscous solutions. In flow-injection analysis, such samples cause refractive index effects and low. broad peaks due to prolonged residence time, these interferences are minimized by the use of a carrier solution (7 w/v % NaCl in 1 M HCl) with same refractive index as the samples, careful pH adjustment, use of knotted coils, and a specially designed detector. Validation of the method in the concentration range 4-40 microg ml(-1) (injected samples) shows a repeatability (n = 6) and day-to-day reproducibility (n = 9) of 0.4-9.2 and 2.3-17.5% RSD respectively. The accuracy is 81(near the lower limit of detection)-101%, with a limit of detection of 1 microg ml(-1). Linearity was shown in the concentration range tested. The method is well suited for in-process analysis, release control and stability testing of both drug substance and drug product. The cost of analysis is reduced compared to the manual method.