Fluorimetric determination of aminocaproic acid in pharmaceutical formulations using a sequential injection analysis system

A sequential injection analysis (SIA) methodology for the fluorimetric determination of aminocaproic acid in pharmaceutical formulations is proposed. The developed analytical procedure is based on the derivatisation reaction of the aminocaproic primary amine with o-phthalaldehyde (OPA) and N-acetylcysteine (NAC) and fluorimetric detection of the formed product (λex = 350 nm; λem = 450 nm). The implementation of a SIA flow system allowed for the development of a simple, fast and versatile automated methodology, which exhibits evident advantages regarding the US Pharmacopoeia 24 (USP 24) reference procedure. By combining the SIA time-based sample insertion with a subsequent zone sampling approach, which permitted to select for detection of a well-defined sample zone, it was possible to implement an on-line dilution strategy that enabled the expansion of the analytical working range of the methodology, and thus its application in dissolution studies, without manifold re-configuration.Linear calibration plots were obtained for aminocaproic acid concentrations up to 6 × 10−5 mol l−1. The developed methodology exhibit a good precision, with a R.S.D. < 2.0% (n = 15) and the detection limit was 2.5 × 10−7 mol l−1. The obtained results complied with those furnished by the reference procedure with a relative deviation lower than 1.2%. No interference was found.