Table 2.

A comparison between the properties of stable labeled [¹³C₁₂] Sucrose and radiolabeled [¹⁴C] Sucrose in measuring brain permeability.

[13C12] Sucrose	[14C] Sucrose
• Stable isotope-labeled.	• Radioactive.
• Commercially available as a powder. Does not degrade over time. Aqueous stock solutions can be frozen and stored for years.	• Commercially available as a solution in ethanol. Degrades over time (∼0.5% per year) and older lots require labor-intensive purification on HPLC before use to get reproducible data.
• Comparatively cheaper.	• Expensive.
• The method of detection is very specific and sensitive to molecular weight. As a result, unwanted artifacts do not affect brain uptake measurements.	• Associated with lipophilic impurities which constitute 80% of brain uptake pharmacokinetically.
• Detection is done through LC-MS/MS which can differentiate entities based on the molecular weight of the compound.	• Detection is done through liquid scintillation counters which are not able to differentiate between actual sucrose uptake and lipophilic impurities.