Abstract <p>A method is proposed for reducing the limit of detection for <i>p</i>-aminobenzoic acid and some of its medicinal derivatives in condensation reactions with <i>p</i>-dimethylaminobenzaldehyde, based on a combination of catalysis by anionic (effect of “micellar catalysis”) and preconcentration by non-ionic surfactants (effect of “micellar microextraction”). The conditions for obtaining saturated micellar phases of Triton X-114 in the absence and in presence of sodium dodecyl sulfate (<b>SDS</b>) ions and micelles, reactants, and salting-out agents (NaCl, Na₂SO₄, Na₃C₆H₅O₇) are optimized. Micellar-saturated phases of Triton X-114 and SDS are proposed as test means, ensuring the effective preconcentration of the analytical forms of Schiff bases of the studied analytes and their determination at the nanogram level in aqueous media, blood plasma model, and dosage forms at concentrations of an order of <i>n</i> × 10^–8 M by colorimetric methods using digital technologies.</p>