ANALYTICAL PERFORMANCE EVALUATION OF COLORIMETRIC METHODS FOR ESTIMATING INDOLE-3-ACETIC ACID, KINETIN, AND GIBBERELLIC ACID IN PLANTAIN (MUSA × PARADISIACA L.) TISSUES

This study evaluated the performance of three colorimetric procedures for estimating indole-3-acetic acid (IAA), gibberellic acid (GA₃), and kinetin in purified extracts of plantain corms (Musa × paradisiaca L.). The extracts were purified using C18 solid-phase extraction cartridges, and colorimetric responses were measured at 530, 540, and 570 nm, respectively. The retained calibration ranges were 0–40 µg mL⁻¹ for IAA, 0–60 µg mL⁻¹ for GA₃, and 0–80 µg mL⁻¹ for kinetin, with coefficients of determination (R²) of 0.9976, 0.9886, and 0.9910, respectively. The estimated limits of detection (LOD) were 5.24, 8.26, and 11.71 µg mL⁻¹, while the limits of quantification (LOQ) were 15.88, 25.03, and 35.48 µg mL⁻¹, respectively. Repeatability and intermediate precision were assessed using coefficients of variation. Recovery tests showed variable results depending on the compound and spiking level. Some calculated concentrations, particularly for IAA and kinetin, exceeded the upper calibration limits and were therefore considered extrapolated estimates. The lack of demonstrated molecular selectivity limits the specific interpretation of the colorimetric responses obtained. These procedures may be used for relative or semi-quantitative comparisons, provided that the established calibration ranges are respected and results are expressed as equivalents of the corresponding standards. However, they cannot replace chromatographic methods when specific identification and quantification are required.