A fluorescent (340/380 nm) photochemical product, identified at m/z 206 by mass spectrometry was obtained by photo-derivatization (15 s ultraviolet exposure) in water/acetonitrile 10/90 v/v. The photoproduct was used for indirect determination of trifloxystrobin in water and soy grape juice by high-performance liquid chromatography and fluorescence detection. Separation was made under isocratic conditions (acetonitrile/water 70/30% v/v, at 1.0 mL min 1 and 35 ºC) with trifloxystrobin photo-derivative eluting at 3.2 min. The influence of ultraviolet exposure was evaluated in short and long terms with photoproduct showing stability up to 120 min after 15 s of ultraviolet exposure. The limit of detection was 57 µg L-1 in water (87-109% recoveries). For soy grape juice, dispersive liquid-liquid micro-extraction was used to clean up and for pre-concentration (limit of detection of 9.5 µg kg 1 and 93-101% recoveries) attending to the maximum residue limits for citrus juices established by regulatory agencies. Potential interference by triazoles was evaluated.

Abstract A low-temperature sintering process was used to produce pellets at different temperatures using TiO2 anatase (Vetec) and P25 (Evonik) commercial powders. The initial powder was mixed with 75% acetic acid aqueous solution and pressed under 375 MPa. The temperature was applied after the pelletization in a conventional furnace for 4 hours. The best sintering temperature for anatase was 800°C, which is higher than typical cold sintering temperatures but below conventional ones. However, the optimal temperature was 450 °C for P25 due to its density and SEM results. The sintered pellets' maximum densities were 70% (anatase, 800oC) and 66% (P25, 450oC). It was not possible to measure the anatase pellets treated under 800oC because they disintegrated in water. This work studied the effects of the applied pressure, solvent concentration, particle size, and sintering temperature on the properties of sintered pellets, such as integrity, density, and presence of porous. It also evaluated the electrochemical activity measured by cyclic voltammetry (CV), which indicated that the sintered TiO2 pellets are porous with a partial capacitive response.

A series of triphenylamino (TPA)-chalcones and triphenylamino-β-arylchalcones, displaying either D-π-D or D-π-A architecture, were synthesized through aldol condensations and Heck reactions. The chalcone derivatives display intense absorption bands ranging from 389 to 432 nm and molar extinction coefficients of ca. 105 L mol-1 cm-1 corresponding to π-π* electronic transitions. The photoluminescence emissions are peaked between 470 and 563 nm with large Stokes shifts (80-131 nm), attributed to charge transfer in the excited state. The dyes present low fluorescence quantum yields, which is attributed to radiationless excited state deactivation related to aryl rings rotation. Spectroscopic and electrochemical methods were used to determine the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels. Both optical and electrochemical properties of the TPA-chalcone derivatives are considerably affected by the substitution pattern of the chalcones aryl rings and also by the β-arylation of the olefin moiety.

A simple and sensitive method has been proposed for the determination of sibutramine-HCl in energy drinks, green tea and pharmaceutical formulations using differential pulse voltammetry performed on a hanging mercury drop electrode. In the chosen experimental condition (Mcllvaine pH 4.0 buffer, 50 mV pulse amplitude and 40 mV s-1 scan velocity), sibutramine-HCl presented a reversible behavior and a peak maximum at -80 mV. Detection limit was 0.4 mg L-1 and the working linear range extended up to 33.3 mg L-1 (r = 0.99). Analysis of real and fortified samples enabled recoveries between 91 and 102%. The electroanalytical method was compared with a HPLC method which indicated it accuracy.

Room-temperature phosphorimetry was used to quantify trace levels of chrysene in sugar-cane spirits and in fish bile. A selective phosphorescence enhancer (AgNO3) and synchronous scanning allowed the detection of ng amounts of chrysene. Accuracy (113 ± 17%) and selectivity was evaluated using the CRM-NIST-1647d - Priority Pollutant Polycyclic Aromatic Hydrocarbons in acetonitrile. Analysis of sugar-cane spirit samples enabled recovery of 108 ± 18% which agreed with the one achieved using HPLC. Method's uncertainty was equivalent to 3.4 ng of the analyte, however, the analyte pre-concentration (SPE) improved sensibility and minimized the relative uncertainty. Characterization and homogeneity studies in fish bile were also performed.

A derivação fotoquímica é proposta como abordagem para induzir fluorescência intensa (412/465 nm) da eritromicina. Parâmetros experimentais importantes como o tempo de irradiação com UV e tipo e concentração de ácido usado para tratar a solução de analito foram ajustadas. Limites de detecção e quantificação de 0,025 e 0,085 µg mL-1 foram obtidos com resposta linear até 200 µg mL-1. O procedimento é seletivo em relação a antibióticos aminoglicosídicos (canamicina, gentamicina e amicacina). O método foi testado em formulações farmacêuticas e em uma vacina contendo eritromicina como conservante, com recuperações do analito entre 98 e 105%.

Photochemical derivatization was proposed to enable intense fluorescence (412/465 nm) from erythromycin. Crucial experimental parameters such as type and concentration of the acid used to treat analyte solutions and UV irradiation time were adjusted. Limits of detection and quantification of 0.025 and 0.085 µg mL-1 were achieved with linear range up to 200 µg mL-1. The procedure was selective towards the presence of aminoglycoside antibiotics (kanamycin, gentamycin and amikacin). The method was tested using pharmaceutical formulations and one vaccine composition containing erythromycin as a preservative component, with analyte recoveries between 98 and 105%.

A method was developed for quantification of Cd and Pb in ethanol fuel by filter furnace atomic absorption spectrometry. Filter furnace was used to eliminate the need for chemical modification, to stabilize volatile analytes and to allow the application of short pyrolysis step. The determinations in samples were carried out against calibration solutions prepared in ethanol. Recovery tests were made in seven commercial ethanol fuel samples with values between 90 and 120%. Limits of detection were 0.1 µg L-1 for Cd and 0.3 µg L-1 for Pb. Certified water samples (APS 1071, APS 1033, NIST 1643d, NIST 1640) were also used to evaluate accuracy and recoveries from 86.8% to115% were obtained.

As características fosforescentes do benzo[b]nafto[2,3-d]tiofeno (BNT) foram estudadas sob diferentes condições experimentais. Melhores resultados foram obtidos utilizando-se Tl(I) e Pb(II) como indutores de fosforescência, em ambos os casos usando dodecilsulfato de sódio (SDS) como modificador de superfície. Nestas duas condições, curvas analíticas de 3 ordens de magnitude forneceram limites de detecção e quantificação de respectivamente 0,6 e 2,0 ng na presença de Tl(I) e 3,2 e 10,7 ng na presença de Pb(II). A potencialidade da metodologia desenvolvida para determinação de BNT em nível de traços foi testada usando amostras de sedimento enriquecidas com o analito de interesse e Pb(II) como átomo pesado seletivo para indução de fosforescência. A recuperação de BNT foi bastante satisfatória (101,5±7,4%, n=6) indicando que o método pode ser aplicado para a análise de amostras complexas. A interferência de outros hidrocarbonetos policíclicos aromáticos (pireno, criseno, carbazol, 7,9-dimetilbenzo[c]acridina e dibenzotiofeno) foi avaliada e o método foi considerado seletivo na presença destas substâncias.

Room-temperature phosphorescence characteristics of benzo[b]naphtho[2,3-d]thiophene (BNT) were studied under several experimental conditions. Best phosphorescence was obtained using Tl(I) and Pb(II) as heavy atom enhancers, both in the presence of SDS as surface modifier. Under these two conditions of maximum phosphorescence, working curves with three orders of magnitude were achieved and absolute limits of detection and quantification of respectively 0.6 and 2.0 ng in the presence of Tl(I) and 3.2 and 10.7 ng in the presence of Pb(II). The RTP potential for selective trace-level determination was tested using a sediment sample spiked with BNT and using Pb(II) as the selective heavy atom enhancer. The recovery of BNT was very satisfactory (101.5 ± 7.4%, n = 6) indicating that the method can be properly applied for the analysis of complex samples. The interference potential from other polycyclic aromatic hidrocarbons (pyrene, chrysene, carbazole, 7,9-dimethylbenz[c]acridine and dibenzothiophene) was evaluated and the method was considered selective in the presence of these substances.