A sensitive high-performance liquid chromatography-fluorescence detection method (HPLC-FLD) was developed and validated for 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) determination in wastewater samples. Sample preparation was performed by solid-phase extraction (SPE) on Hypersep C18 cartridges. Conditioning and elution solvents and sample volume were investigated by a 23 factorial design for both analytes. The pre-concentration factor was 2500 times, allowing to quantify 5.0 ng L-1 for both hormones. The SPE-HPLC-FLD method was successfully applied to detect and quantify trace amount of target compounds in raw and treated wastewater samples. E2 was found below limit of quantification in influent and effluent samples. Nevertheless, the recoveries of E2 in standard addition experiments were between 41 and 72%, with relative standard deviations between 4 and 16%. An important matrix effect was observed in the determination of EE2, with fluorescence signal suppression.

Two simple and efficient procedures have been developed for the rapid simultaneous determination of compounds with mutual spectral interference (rifampicin (RIF) and isoniazid (INH)). The first method was based on the UV–Vis spectral signal (190–600 nm) of synthetic RIF and INH aqueous solutions, whereas the second method involved the visible spectral signal registered between 350 and 800 nm after the reaction of INH with a Cu2+/neocuproine complex. Both multivariate spectrophotometric methods show excellent prevision capacity, providing results that are statistically equivalent with those provided by the standard chromatographic procedure. The methods were validated according to criteria established by ANVISA, showing precision, accuracy and robustness compatible with the requirements for new analytical methods, additionally allowing the reduction of waste generation.

O método de regressão por mínimos quadrados parciais (PLSR) foi utilizado para a quantificação simultânea de dois tuberculostáticos rifampicina (RIF) e isoniazida (INH) por espectrofotometria na região do visível utilizando uma reação de derivatização simples. Na presença de neocuproína, íons cobre(II) foram facilmente reduzidos por INH para um complexo Cu(I)-neocuproína de absorção máxima a 455 nm. Sob essas mesmas condições, RIF mostrou uma absorção máxima a 449 nm. O conjunto de calibração foi estabelecido entre 8 e 57 mg L-1 de RIF e 1,5 e 7 mg L-1 de INH. O método foi aplicado para a determinação das drogas em amostras de urina (recuperações entre 92 e 119%) e em formulações farmacêuticas (erro relativo inferior a 5%).

Partial least squares regression (PLSR) was used for the simultaneous quantification of rifampicin (RIF)and isoniazid (INH) by visible spectrophotometry using a simple derivatization reaction. In the presence of neocuproine, copper(II) is easily reduced by INH to a Cu(I)-neocuproine complex that shows an absorption maximum at 455 nm. Under these conditions, RIF shows an absorption maximum at 449 nm. The calibration set was established between 8and 57 mg L-1 for RIFand 1.5and 7 mg L-1 for INH. The method was applied to the determination of the drugs in urine samples (recoveries between 92and 119%)and in pharmaceutical formulations (relative error lower than 5%).

A multivariate spectrophotometric method was developed for analysis of kojic acid/hydroquinone associations in skin whitening cosmetics. The method is based on the reaction between kojic acid and Fe3+ and on the reduction of Fe3+ by hydroquinone and further complexation of Fe2+ with 1,10-phenanthroline. The multivariate model was developed by Partial Least Squares Regression (PLSR), using 25 synthetic mixtures and mean-centered spectral data (350-380 nm). The use of 3 (kojic acid) and 2 (hydroquinone) latent variables permits the observation of mean errors of about 5% in the external validation phase.