8 documents found, page 1 of 1
Introducing the concept of centergram: a new tool to squeeze data from separati...
Erny, Guillaume L.; Simó, Carolina; Cifuentes, Alejandro; Esteves, Valdemar I.tIn separation techniques hyphenated to mass spectrometry (MS) the bulk from the separation step iscontinuously flowing into the mass spectrometer where the compounds, arriving at each separationtime, are ionized and further separated based on their m/z ratio. An MS detector is recognized as beinga universal detector, although it can also be a very selective instrument. In spite of these advantages,classical tw...
Immobilized humic substances and immobilized aggregates of humic substances as ...
Erny, Guillaume L.; Gonçalves, Bruna M.; Esteves, Valdemar I.In this work, humic substances (HS) immobilized, as a thin layer or as aggregates, on silica gel were tested as material for solid phase extraction. Some triazines (simazine, atrazine, therbutylazine, atrazine-desethyl-desisopropyl-2-hydroxy, ametryn and terbutryn), have been selected as test analytes due to their environmental importance and to span a large range of solubility and octanol/water partition coeff...
Dynamically formed admicelle layer to control the amplitude of cathodic electro...
Erny, Guillaume L.; Gonçalves, Bruna M.; Esteves, Valdemar I.In this manuscript, a method to precisely adjust the amplitude of a cathodic electroosmotic flow is described. The method uses a capillary pre-coated with a cationic polymer (polybrene), in presence of an anionic surfactant such as sodium dodecyl sulfate. At low concentration of surfactant, molecules will self-assemble to form an immobilized hemimicelle layer with the anionic "head" in contact with the cationic...
Direct photodegradation of carbamazepine followed by micellar electrokinetic ch...
Calisto, Vania; Erny, Guillaume L.; Esteves, Valdemar I.; Domingues, M. Rosario M.Carbamazepine, a widely consumed psychotropic pharmaceutical, is one of the most commonly detected drugs in the environment. To better assess the environmental persistence of carbamazepine in aqueous matrices, the effect of pH and dissolved oxygen on the direct photodegradation rate of this pharmaceutical was evaluated in this study, using simulated solar irradiation. In order to follow the degradation and the ...
Studying the interaction between triazines and humic substances-A new approach ...
Erny, Guillaume L.; Calisto, Vania; Lima, Diana L. D.; Esteves, Valdemar I.The strength of the interaction between a pesticide and the soil organic matter is a key parameter to assess the risk of it reaching to groundwater with potentially harmful effects to human health. In this work, a new approach that allows measuring such interactions in a few minutes using a purified fraction of the soil organic matter (humic substances) is detailed. The strength of sorption is assessed via the ...
Comparison between MEKC and UV spectral deconvolution to follow sorption experi...
Lima, Diana L. D.; Silva, Carla Patricia; Erny, Guillaume L.; Esteves, Valdemar I.In this study a simple and rapid procedure for monitoring sorption of atrazine onto soil samples was developed This method is based on a multiwavelength UV spectral deconvolution (UVSD) where the UV spectrum of a sample is considered as a linear combination of absorption spectra, named reference spectra. The combination of the reference spectra allows the restitution of the shape of the UV spectrum of any unkno...
Robustness of the co-ion transfer ratio in capillary electrophoresis
Erny, Guillaume L.; Esteves, Valdemar I.In CE, indirect detection mode often exhibits a lower precision than its direct counterpart. Although various explanations have already been advanced, in this work, we aimed to investigate if this is due, in part, to problems of robustness of the coion transfer ratio (TR), thus being inherent to this particular detection scheme. This was investigated using simulation software that allows an accurate control of ...
Analysis of Non-Aromatic Organic Acids in Beer by CE and Direct Detection Mode ...
Erny, Guillaume L.; Rodrigues, Joao E. A.; Gil, Ana M.; Barros, Antonio S.; Esteves, Valdemar I.A method for the analysis of the main non-aromatic organic acids in beer using capillary electrophoresis is presented. In this work, malic, citric, succinic, pyruvic, acetic and lactic acids are separated using a sodium hydrogen phosphate background electrolyte with direct detection mode with a diode array detector. The separation exhibits lower sensitivity than equivalent methods with indirect detection mode, ...