In this paper, Cu-doped carbon quantum dots (Cu-CQDs) were prepared by carrying out thermolysis of Na2[Cu(EDTA)] and hydroxylamine hydrochloride at 300 ºC for 2 h. The as-prepared Cu-CQDs were characterized by UV-Vis, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The Cu-CQDs exhibited good fluorescence property, high stability, excitation-dependent emission behavior and a quantum yield of 9.8%. More significantly, the synthesized Cu-CQDs were developed for sensing rutin (RT) based on the fluorescence quenching of the prepared Cu-CQDs. A good linear relationship between the fluorescence quenching of Cu-CQDs and different concentrations of RT was obtained in the range of 0.1-15 µg mL-1 with a correlation coefficient of 0.9959. The detection limit was as low as 0.05 µg mL-1 (signal-to-noise ratio, S/N = 3). The possible mechanism of fluorescence quenching was explored, which was proved to be inner filter effect. Importantly, the proposed method was successfully applied in the detection of RT tablet samples and with satisfactory results, showing the practical applications.

A novel extraction technique combining dispersive liquid-liquid microextraction (DLLME) with magnetic solid-phase extraction (MSPE) is presented for pre-concentration of four primary aromatic amines (PAAs) released from azo dyes in paper samples prior to high performance liquid chromatography (HPLC). n-Octanol was used as the extractant and hydrophobic oleic acid modified Fe3O4 nanoparticles (Fe3O4@OA NPs) as an efficient adsorbent was applied to retrieve the PAAs-containing n-octanol in the DLLME step. Because of the rapid mass transfer associated with the DLLME and MSPE steps, fast extraction could be achieved. The main parameters affecting the efficiency of MSPE-DLLME procedure of PAAs were investigated and optimized. Under optimum conditions, the recoveries ranged from 79.6 to 88.5% and the limits of detection (LODs) were in the range of 0.21-1.16 ng mL-1 (S / N = 3). The intra-day precision (relative standard deviation (RSD)) was below 7.8% and inter-day RSD was less than 11%.

A new method using nonanoic acid-coated magnetic Fe3O4 nanoparticles as adsorbent has been developed for the single-step extraction and preconcentration of lead and copper in tobacco samples. Transmission electron microscopy and X-ray diffraction spectrometry were used to characterize the adsorbent. The experimental parameters affecting extraction efficiency, including amount of nanoparticles, volume of chelating reagents, sample pH, ultrasonic time and desorption conditions were investigated. The analytes desorbed from nanoparticles were determined by flame atomic absorption spectrometry. Under the optimum conditions, good linearity was obtained in the range of 2-400 µg L-1 for copper and 5-800 µg L-1 for lead (r > 0.998, p < 0.05). The limits of detection for copper and lead were 0.2 and 0.5 µg L-1, with enrichment factors of 45 and 52, respectively. The method was successfully employed to tobacco sample analysis and got excellent recoveries between 89.2 and 100.7% with relative standard deviations (n = 6) of 4.5-5.9%.

Oleic acid modified Fe3O4 nanoparticles were proposed for magnetic solid-phase extraction coupled with ultra high-performance liquid chromatography-tandem mass spectrometry to determine risperidone (RISP) and 9-hydroxyrisperidone (9OHR) in biological samples. The effects of various experimental parameters including adsorbent amount, pH, adsorption time, eluent type and concentration were systematically investigated. Under optimal conditions, the calibration curve was linear within the concentration range of 0.2-200 ng mL-1 with the correlation coefficient (r) of 0.9962 and the lower limit of quantification was 0.06 ng mL-1 for RISP; the calibration curve was linear within the concentration range of 0.2-200 ng mL-1 with the correlation coefficient of 0.9956 and the lower limit of quantification was 0.04 ng mL-1 for 9OHR. The extraction recoveries were over 90.0% with relative standard deviation less than 5.0%. All these results suggested that magnetic extraction method can be used for enrichment and quantification of RISP and 9OHR in biological samples.

Neste estudo, uma microextração em fase líquida suportada em fibra oca e com agitação vórtex (VA-HF-LPME) acoplada à cromatografia líquida de alta performance (HPLC) foi desenvolvida para a determinação de três compostos endócrinos sintéticos desreguladores [EDCs, bisfenol-A (BPA), bisfenol-AF (BPAF) e tetrabromobisfenol-A (TBBPA)] em amostras de leite. A agitação vórtex forneceu uma mistura efetiva e moderada das soluções de amostra e aumentou o contato entre os analitos e as camadas de fronteira da fibra oca, aumentando assim a razão de transferência de massa e levando à uma alta eficiência de extração dos analitos alvo. Os parâmetros que influenciaram o método de preparação da amostra do VA-HF-LPME, como os solventes orgânicos (fase aceptora), pH da solução da amostra (fase doadora), volume da amostra, concentração de NaOH, tempo de extração e força iônica, foram sistematicamente otimizados. As curvas de calibração instrumental do BPA, BPAF e TBBPA mostraram boas relações lineares (R² > 0,9988) na faixa de concentração de 0,5-200, 0,5-200 e 1,0-250 µg L-1, respectivamente. O desvio relativo padrão (RSD, n = 5) estava entre 1,3-3,7%. Os limites de detecção (LOD, S/N = 3) estavam na faixa de 0,16-0,35 µg L-1 e os limites de quantificação (LOQ, S/N = 10) na faixa de 0,51-1,12 µg L-1. O método proposto foi aplicado com sucesso na extração de EDCs em amostras de leite.

In this study, a vortex-assisted three-phase hollow fiber liquid-phase microextraction (VA-HF-LPME) coupling with high performance liquid chromatography (HPLC) method was developed for determination of three synthetic endocrine disrupting compounds[EDCs, bisphenol-A (BPA), bisphenol-AF (BPAF) and tetrabromobisphenol-A (TBBPA)] in milk samples. Vortex provided effective and mild mixing of the sample solution and increased the contact between analytes and boundary layers of the hollow fibre, thereby enhancing mass transfer rate and leading to high extraction efficiency of the target analytes. The influencing parameters of VA-HF-LPME sample preparation method, such as organic solvents (acceptor phase), pH of sample solution (donor phase), sample volume, concentration of NaOH, extraction time, and ionic strength were systematically optimized. The instrumental calibration curves of BPA, BPAF and TBBPA show good linear relations (R² > 0.9988) in the concentration range of 0.5-200, 0.5-200 and 1.0-250 µg L-1, respectively. The relative standard deviations (RSD, n = 5) were 1.3-3.7%. The limits of detection (LOD, S/N = 3) were in the range of 0.16-0.35 µg L-1 and the limits of quantification (LOQ, S/N = 10) were in the range of 0.51-1.12 µg L-1. The proposed method was successfully applied to the extraction of EDCs in milk samples.

Desenvolveu-se um procedimento de microextração por emulsificação assistida por ultrassom e aperfeiçoada por surfactante (UASEME) combinado com cromatografia líquida de alta eficiência com detector de arranjo de diodos para a determinação de 17b-estradiol (βE2), estrona (E1) e dietilestilbestrol (DES) em água. Ultrassom foi aplicado para auxiliar a emulsificação e Triton X-100 foi usado como dispersor e emulsificante. Tetracloreto de carbono foi usado como solvente extrator. Empregando otimização global, o procedimento foi caracterizado por um intervalo linear aceitável de 10 a 1000 ng mL-1 para βE2, E1 e DES (r > 0,997), exatidão e precisão validadas (RSD 0,85-1,28% (n = 5)) e alta sensibilidade com limites de detecção de 0,200, 0,100 e 0,125 ng mL-1 para βE2, E1 e DES, respectivamente. O procedimento foi aplicado para a análise de amostras típicas de água, com fatores de enriquecimento de 85,29, 173,45 e 97,05 para βE2, E1 e DES, respectivamente, e boas recuperações (≥ 89,82%). De maneira geral, o procedimento desenvolvido foi simples e confiável, com potencial de aplicação em larga escala para análises da água.

An ultrasound-assisted surfactant-enhanced emulsification microextraction (UASEME) combined with high performance liquid chromatography-diode array detector procedure was developed for the determination of 17β-estradiol (βE2), estrone (E1) and diethylstilbestrol (DES) in water. Ultrasound was applied to assist emulsification, and Triton X-100 was adopted as the disperser and emulsifier. Carbon tetrachloride was applied as the extraction solvent. Global optimization was used and the developed procedure was characterized by an acceptable linear range of 10 to 1000 ng mL-1 for βE2, E1 and DES (r > 0.997), a validated accuracy and precision (RSD 0.85-1.28% (n = 5)), and high sensitivity with limits of detection of 0.200, 0.100 and 0.125 ng mL-1 for βE2, E1 and DES, respectively. Furthermore, we applied this procedure to analyze typical water samples, with enrichment factors of 85.29, 173.45 and 97.05 for βE2, E1 and DES, respectively, and good recoveries (≥ 89.82%). Altogether, the proposed procedure was simple and reliable, with potential application in large-scale water analysis.