Determination of Hardness of a Pharmaceutical Oral Jelly by Using T Relaxation Behavior Measured by Time-Domain NMR.

Hardness is a critical quality characteristic of pharmaceutical oral jelly. In this study, the hardness was determined by using the T relaxation curves measured by time-domain NMR. For sample preparation, kappa- and iota-carrageenans, and locust bean gum, were used as gel-forming agents. Ten test jellies with different gel-forming agent composition were prepared, and their hardness and T relaxation curves were measured by a texture analyzer and time-domain NMR (TD-NMR). A negative correlation between T relaxation time (T) and hardness was observed; however, it was difficult to determine the hardness directly from the T value. That is probably because the T relaxation curve contains information about molecular states, not only of water but also of the solute, and T values calculated by single-exponential curve fitting only express one property of the test jelly. By considering this issue, partial least squares (PLS) regression analysis was performed on the T relaxation curves for hardness determination of the test jellies. According to the analysis, an accurate and reliable PLS model was created that enabled accurate assessment of the hardness of the test jellies. TD-NMR enables the measurement of samples nondestructively and rapidly with low cost, and so could be a promising method for evaluation of the hardness of pharmaceutical oral jellies.