As described in Sections 4.3-4.5, the NaNO3 solution in the lucigenin assay can be readily replaced by solutions of other salts to study transport processes different from Cl -/NO3 -antiport. However, certain salt solutions cannot be employed in the lucigenin assay. For example, sodium gluconate and N-methylᴅ-glucamine-based salts (such as NMDGH + NO3 -are commonly used in transport studies, but are not compatible with lucigenin. When dissolved in solutions with these carbohydrate-based salts, the lucigenin changes colour and loses its fluorescence over time, most likely due to decomposition following oxidation. Lucigenin can be dissolved in a solution of sodium phosphate rather than NaNO3 without any problem, but this system cannot be used to study Cl -/H2PO4 -antiport, because the buffering capacity of the solution is high enough for Cl -/OH -antiport or H + Cl -symport to take place. This results in a transport response by any compound that can perform Cl -/OH -or H + Cl -transport and does not inform on the ability of a compound to perform Cl -/H2PO4 -antiport.