Content determination of amlodipine besylate tablet by quantitative nuclear magnetic resonance spectroscopy

To established a quantitative nuclear magnetic resonance spectroscopy (qNMR) method for the content determination of amlodipine besylate tablets. The tablet sample was grounded and weighted before mixing with methal-d4 as solvent,1,3,5-trimethoxybenzene as internal standard. The mixture was votexed and centrifuged to achive good separation. The upper layer solution was quantitatively analyzed by 1 H-NMR. The peaks of δ 5.41from amlodipine besylate and δ 6.07 from 1,3,5-trimethoxybenzene were selected as quantitative peak and reference peak,respectively. Parameters used in 1 H-NMR are:90 degree single pulse sequence,delay time 30 s,number of scans 32 and probe temperature 308 K. A good linear relationship was established for amlodipine besylate and 1,3,5-trimethoxybenzene between molar ratio range of 0.42-8.38 with correlative coefficient of 0.9973. Repeatability and Intermediate precision evaluation showed a relative standard deviation (RSD) of 0.45% (n=7) and 0.44% respectively. The robustness of this method was validated with a RSD of 1.69% (n=6). The spiked recoveries for amlodipine besylate tablet sample were 103.86%,101.20% and 99.69% for 3 sets of experiments. The established qNMR method was applied to analyze amlodipine besylate tablets from 8 different brands and the results showed this method is reliable and convenient with high precision and good repeatability,which could be apply as a general method for the content determination of medical tablets.