Orthogonal methods/techniques are like 2-factor authentication of research results. Each experimental technique has (unintentional) measurement biases and artifacts, but these differ from technique to technique, depending on the physical principle they use to collect evidence. Thus, multiple techniques based on different properties can be combined to verify a result.
Orthogonal measurements are a type of complementary measurement, but not all complementary measurements are orthogonal.
According to Simon, C. G et al. Journal of Controlled Release, 2023 (and adopted by NIST:
Orthogonal measurements are “measurements that use different physical principles to measure the same property of the same sample with the goal of minimizing method-specific biases and interferences.”
And
Complementary measurements are “measurements that corroborate each other to support the same decision”
Basically, you use two or more techniques to measure the same “property” of a sample (e.g. aggregation propensity, particle size) based on different types of experimental evidence (e.g. hydrodynamic radius via size exclusion chromatography (SEC), interaction with light via dynamic light scattering (DSLS), interaction with gravitational field with analytical ultrafiltration (AUC), etc.).
Some good resources if you want to learn more:
Orthogonal Measurements. NIST 2023. https://www.nist.gov/programs-projects/orthogonal-measurements
Simon, C. G.; Borgos, S. E.; Calzolai, L.; Nelson, B. C.; Parot, J.; Petersen, E. J.; Roesslein, M.; Xu, X.; Caputo, F. Orthogonal and Complementary Measurements of Properties of Drug Products Containing Nanomaterials. Journal of Controlled Release 2023, 354, 120–127. https://doi.org/10.1016/j.jconrel.2022.12.049.
Simon, C. G.; Bozenhardt, E. H.; Celluzzi, C. M.; Dobnik, D.; Grant, M. L.; Lakshmipathy, U.; Nebel, T.; Peltier, L.; Ratcliffe, A.; Sherley, J. L.; Stacey, G. N.; Taghizadeh, R. R.; Tan, E. H. P.; Vessillier, S. Mechanism of Action, Potency and Efficacy: Considerations for Cell Therapies. J Transl Med 2024, 22 (1), 416. https://doi.org/10.1186/s12967-024-05179-7.
Increasing regulatory focus on orthogonal analytical characterization for biosimilars. https://gabionline.net/sponsored-articles/increasing-regulatory-focus-on-orthogonal-analytical-characterization-for-biosimilars
More on bioorthogonal chemistry: blog: https://bit.ly/bioorthogonal_prize ; YouTube: https://youtu.be/LrwzFRY7gsk
More on caution with false hits: https://youtu.be/ot2kB1gKWZk
More on experimental artifacts: https://thebumblingbiochemist.com/365-days-of-science/artifacts/ & https://youtu.be/pas66G5gtmg
More on antibody-based techniques: http://bit.ly/antibodytypesanduses
More on mass spectrometry: https://thebumblingbiochemist.com/365-days-of-science/tandemmassspec/
More on mass photometry: https://thebumblingbiochemist.com/365-days-of-science/mass-photometry/ & https://youtu.be/CDg9GTkC_78
