A simple method for the identification and assay of iopamidol and iothalamate meglumine in pharmaceutical samples based on proton nuclear magnetic resonance spectroscopy

A proton nuclear magnetic resonance (PMR) spectroscopic method is described for the direct assay and identification of the triiodinated radiographic c ontrast agents iopamidol (nonionic type) and iothalamate meglumine (ionic t ype) in commercial solutions and as a bulk material. Samples were prepared by simply diluting an injectable solution with or dissol ving a powdered sa mple in D2O. Sodium acetate was added to serve as an internal standard. Qua ntitations were based on the resonance signals for the protons of the CH3-C O-group at 1.58 ppm (iopamidol) or 2.25 ppm (iothalamate), CH3-N-group at 2 .38 ppm (meglumine) and CH3-CO-group at 1.92 ppm (acetate). The mean +/-SD (n = sets of 10 samples each) recovery of iopamidol, iothalamic acid and me glumine from synthetic mixtures with the internal standard were 99.6 +/- 0. 63. 99.7 +/- 0.66 and 99.9 +/- 1.18%, respectively; with the values ranging from 98.7-100.9% for iopamidol and iothalamate, and from 98.3-100.8% for m eglumine.