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Yes, there are assays that can selectively detect dicarboxylic acids while discriminating against monocarboxylic acids.

Selective Detection Methods

Fluorescent Probes

• Several studies have developed "turn-on" fluorescent probes based on diamidine derivatives (such as 9-(diphenylmethylene)fluorene-based or 1,8-diphenylnaphthalene-based diamidines) that show high selectivity for dicarboxylic acids over monocarboxylic acids13. These probes exploit the ability of dicarboxylic acids to form stable complexes with the sensor, leading to a significant fluorescence response that is not observed with monocarboxylic acids.

Fluorimetric Derivatization

• A highly sensitive and selective fluorimetric method uses intramolecular excimer-forming fluorescence derivatization with 4-(1-pyrene)butyric acid hydrazide (PBH)4. Dicarboxylic acids react to form dipyrene-labeled derivatives that emit excimer fluorescence (450–550 nm), which is distinct from the normal fluorescence of monopyrene-labeled monocarboxylic acids (370–420 nm). This allows for clear discrimination between dicarboxylic and monocarboxylic acids.

Assembly-Induced Emission (AIE)

• A triazine-based fluorinated AIEgen has been reported to recognize dicarboxylic acids with selectivity based on the relative position of the two carboxyl groups10. This approach leverages the assembly behavior of dicarboxylic acids, which is not replicated by monocarboxylic acids, leading to selective fluorescence signaling.

Colorimetric Assays

• There are colorimetric reactions using reagents such as acetic anhydride in the presence of sodium salts that can selectively detect specific dicarboxylic acids (e.g., α-ketoglutaric and oxaloacetic acids) and distinguish them from monocarboxylic acids under certain conditions7. However, this selectivity may be limited to certain structural classes of acids.