Antibiotics are widely used in veterinary medicine mainly for treatment and prevention of diseases. The aminoglycosides are one of the antibiotics classes that have been extensively employed in animal husbandry for the treatment of bacterial infections, but also as growth promotion. The European Union has issued strict Maximum Residue Levels (MRLs) for aminoglycosides in several animal origin products including bovine milk, bovine, swine and poultry muscle. This paper describes a fast and simple analytical method for the determination of ten aminoglycosides (spectinomycin, tobramycin, gentamicin, kanamycin, hygromycin, apramycin, streptomycin, dihydrostreptomycin, amikacin and neomycin) in bovine milk and bovine, swine and poultry muscle. For sample preparation, an extraction method was developed using trichloroacetic acid and clean up with low temperature precipitation and C18 bulk. Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) was used to carry out quantitative analysis and liquid chromatography-quadrupole-time of flight-mass spectrometry (LC-QTOF-MS) was used to screening purposes. Both methods were validated according to the European Union Commission Directive 2002/657/EC. Good performance characteristics were obtained for recovery, precision, calibration curve, specificity, decision limits (CCα) and detection capabilities (CCβ) in all matrices evaluated. The detection limit (LOD) and quantification limit (LOQ) were ranging from 5 to 100ngg(-1) and 12.5 to 250ngg(-1), respectively. Good linearity (r)-above 0.99-was achieved in concentrations ranging from 0.0 to 2.0×MRL. Recoveries ranged from 36.8% to 98.0% and the coefficient of variation from 0.9 to 20.2%, noting that all curves have been made into their own matrices in order to minimize the matrix effects. The CCβ values obtained in qualitative method were between 25 and 250ngg(-1). The proposed method showed to be simple, easy, and adequate for high-throughput analysis of a large number of samples per day at low cost.

Sílica gel modificada com grupos orgânicos tem sido muito utilizada como fase estacionária para cromatografia líquida. Reações de enxerto podem ser usadas na obtenção de superfícies modificadas estáveis de sílica gel. Neste trabalho a sílica gel (10 nm de diâmetro de poro e 320 m 2 g -1 de área superficial) foi modificada quimicamente com 3-cloropropiltrimetoxisilano ou com 3-aminopropiltrimetoxisilano e posteriormente com anilina, p-anisidina, benzilamina e 3-fenilpropilcloreto a fim de se obter grupos aromáticos imobilizados na superfície de sílica gel. A espectroscopia no infravermelho foi utilizada para a caracterização dos grupos aromáticos enxertados, usando-se uma cela de quartzo. Os sólidos foram aquecidos a várias temperaturas em alto vácuo sendo que as áreas sob as bandas dos grupos orgânicos obtidas no infravermelho foram usadas para estimar a estabilidade térmica.Silica gel modified with organic groups is widely used as a stationary phase for liquid chromatography. Grafting synthesis can be used to obtain stable modified silica gel surfaces. In this work, silica gel (10 nm of pore diameter and surface area of 320 m 2 g -1 ) was chemically modified with 3-chloropropyltrimethoxysilane or 3-aminopropyltrimethoxysilane and reacted with aniline, p-anisidine, benzylamine and 3-phenylpropylchloride in order to yield aromatic groups immobilized on the silica gel surface. Infrared spectroscopy was utilized for characterization of the aromatic groups grafted on the silica gel surface, using a quartz cell. The solids were heated at several temperatures in high vacuum and the infrared band areas of the organic groups were used to evaluate the thermal stability.

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A 2 3 factorial design was employed to find the best conditions of pH, L-phenylalanine concentration and temperature for the production of 2-phenylethanol by Kluyveromyces marxianus CBS 6556. The cultivation was carried out on grape must, which contains a great amount of nitrogen compounds. Central composite design (CCD) was used for the analysis of treatment combinations. Results showed a second-degree polynomial regression model with good agreement of experimental data, with R 2 = 0.92015 (p < 0.05). The maximum production of 2-phenylethanol was found at pH 7.0, temperature of 37°C, and a concentration of 3.0 g of L-phenylalanine L -1 . Further experiments in bioreactors showed that oxygen concentration is also important to 2-phenylethanol production, with best results obtained at oxygen mass transfer rates of 2.0 h -1 .

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