Flow and sequential injection methods for the spectrofluorimetric determination of aluminium in pharmaceutical products using chromotropic acid as chromogenic reagent

This work reports rapid and sensitive FI and SI spectrofluorimetric methods for the determination of aluminium in pharmaceutical formulations. The methods are based on the reaction of aluminium with chromotropic acid (CA) in acidic medium to form a water-soluble complex (λex. = 360 nm, λem. = 385 nm). The proposed methods were validated in terms of linearity, repeatability, detection limit, accuracy and selectivity. The calibration curves were linear over the range of 0.03–2.0 and 0.1–4.0 mg/l of aluminium using the FI and SI assays, respectively. The repeatabilities (sr = 0.8% and 1.1% at 1 mg/l aluminium using the FI and the SI assay, respectively, n = 12) were satisfactory. The FI and SI methods proved to be adequately selective and sensitive with respective 3σ limits of detection equal to cL = 0.01 and 0.03 mg/l Al(III). The sampling rates were 120 and 72 h−1 with the FI and SI assay. The methods were applied successfully to the analysis of pharmaceutical formulations (tablets and suspensions). The results were in good agreement with those by an official reference method and the nominal values of the pharmaceutical products.