Related Experiment Video
Updated: Jun 15, 2025

Quantification of the Immunosuppressant Tacrolimus on Dried Blood Spots Using LC-MS/MS
Published on: November 8, 2015
Instability of 7-aminoclonazepam in frozen storage conditions
Jayme L Dahlin1,2, Athena K Petrides1,2
1Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA.
Abstract:
Drug monitoring of benzodiazepines is often performed in toxicology and pain management settings. During the validation of a laboratory-developed multiplex UPLC-MS/MS assay for quantifying benzodiazepines in human urine, we observed notable instability (greater than 20% nominal) in 7-aminoclonazepam (7AC) during prolonged freezing conditions by performing method comparisons and a conventional analyte stability study. These findings highlight the importance of proper calibrator storage and also the essential need to perform method comparison and analyte stability studies. It is recommended that clinical laboratories testing for urine 7AC carefully validate its stability if subjected to freezing conditions.
Related Concept Videos
Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...
Stability of Substituted Cyclohexanes
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
Freezing Point Depression and Boiling Point Elevation
The boiling point of a liquid is the temperature at which its vapor pressure is equal to ambient atmospheric pressure. Since the vapor pressure of a solution is lowered due to the presence of nonvolatile solutes, it stands to reason that the solution’s boiling point will subsequently be increased. Vapor pressure increases with temperature, and so a solution will require a higher temperature than will pure solvent to achieve any given vapor pressure, including one...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
¹H NMR of Labile Protons: Temporal Resolution
The –OH proton in alcohols typically appears in the range of δ 2 to 5 ppm but can vary depending on the specific...

