Skip to main content
. Author manuscript; available in PMC: 2020 Mar 20.
Published in final edited form as: J Pharm Biomed Anal. 2018 Dec 19;166:105–112. doi: 10.1016/j.jpba.2018.12.028

Table 10:

Oxytocin Content by qNMR

Replicates Oxytocin content by qNMR using caffeine as the internal standard (mg/vial) Oxytocin content by qNMR using maleic acid as the internal standard (mg/vial)
1 1.863 1.806
2 1.802 1.818
3 1.793 1.831
Average 1.819 1.818
%RSD 2.1% 0.7%

Note that selection of an appropriate internal standard is crucial for the result. Some desired characteristics of the standard are: 1) ability to provide unique and stable signals (chemical shifts), 2) high purity material is available, 3) soluble in different NMR solvents, 4) easy handling for tasks such as weighing and transfer, 5) non-volatile, 6) non-reactive, and 7) stable in the long term5.