Publications by authors named "Luiz Henrique de Oliveira"

In this paper, we present a new design for a chronoamperometric flow cell in which air bubbles do not interfere with the control of potential between the working and reference electrodes. The flow-through dual-detection cell consists of two independent parts: an upper compartment containing a quiescent supporting electrolyte solution and a channel that operates under hydrodynamically controlled conditions. In this system, the working and counter electrodes can be placed directly in contact with both compartments, whereas the reference electrode can be assembled to be either isolated or in contact with the flowing stream channel.

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A procedure based on liquid-liquid extraction (LLE) and phase separation using magnetically stirred salt-induced high-temperature liquid-liquid extraction (PS-MSSI-HT-LLE) was developed to extract and pre-concentrate ciprofloxacin (CIPRO) and enrofloxacin (ENRO) from animal food samples before electroanalysis. Firstly, simple LLE was used to extract the fluoroquinolones (FQs) from animal food samples, in which dilution was performed to reduce interference effects to below a tolerable threshold. Then, adapted PS-MSSI-HT-LLE protocols allowed re-extraction and further pre-concentration of target analytes in the diluted acid samples for simultaneous electrochemical quantification at low concentration levels.

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A baseline-corrected second-order derivative procedure and a miniaturized sample preparation based on low-density solvent and ultrasound-assisted liquid-liquid microextraction (LDS-UA-LLME) was combined to provide the simultaneous electroanalysis of three fluoroquinolones (FQ) as emerging contaminants (ECs). The enhanced mathematical processing provided the best separation with an accurate measurement of the overlapping peaks during the simultaneous electro-oxidation of target FQs that were directly dropped on the surface of carbon nanofiber-modified screen-printed electrodes. The adapted LDS-UA-LLME protocol was the key step involved in the sample preparation, which preconcentrate target analytes from diluted tap water samples with an enrichment factor of around 80×, allowing their quantification at trace levels.

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Background: We aimed to establish values and parameters using multislice reconstruction in axial computerized tomography (CT) in order to quantify the erosion of the glenoid cavity in cases of shoulder instability.

Methods: We studied two groups using CT. Group I had normal subjects and Group II had patients with shoulder instability.

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