The dielectric barrier discharge ionization detector (BID) is one of the most modern detectors commercially available for gas chromatography (GC). Its technology based on the sample ionization through the energy released from the helium plasma generation process gives it the ability to act as a universal detector and a greater response to various types of compounds compared to the well-established flame ionization detector (FID). In this study, polycyclic aromatic hydrocarbons (PAHs), organophosphates (OPPs) and organochlorines pesticides (OCPs) were investigated. The parameters that could explain the performance of the BID and FID detectors were: structural factors, ionization energy (IE) and energy of the highest occupied molecular orbital (EHOMO), which were obtained by density functional theory (DFT). The relative (BID/FID) responses to PAHs and pesticides were about 1.8 and 3.0 times greater than FID, respectively. Less structural dependence of the BID signal compared to the FID signal was observed. Among the parameters calculated by DFT, the IE was the one that most seemed to have influenced the response of the two detectors studied. The theoretical data proved to be quite consistent to explain the trends observed experimentally, especially to the BID.

Methyl mercury (MeHg) is highly neurotoxic, affecting visual function in addition to other central nervous system functions. The effect of mercury intoxication on the amplitude of horizontal cell responses to light was studied in the retina of the fish Hoplias malabaricus. Intracellular responses were recorded from horizontal cells of fish previously intoxicated with MeHg by intraperitoneal injection (IP group) or by trophic exposure (T group). Only one retina per fish was used. The doses of MeHg chloride administered to the IP group were 0.01, 0.05, 0.1, 1.0, 2.0, and 6.0 mg/kg. The amplitudes of the horizontal cell responses were lower than control in individuals exposed to 0.01 (N = 4 retinas), 0.05 (N = 2 retinas) and 0.1 mg/kg (N = 1 retina), whereas no responses were recorded in the 1.0, 2.0, and 6.0 mg/kg groups. T group individuals were fed young specimens of Astyanax sp previously injected with MeHg corresponding to 0.75 (N = 1 retina), 0.075 (N = 8 retinas) or 0.0075 (N = 4 retinas) mg/kg fish body weight. After 14 doses, one every 5 days, the amplitude of the horizontal cell response was higher than control in individuals exposed to 0.075 and 0.0075 mg/kg, and lower in individuals exposed to 0.75 mg/kg. We conclude that intoxication with MeHg affects the electrophysiological response of the horizontal cells in the retina, either reducing or increasing its amplitude compared to control, and that these effects are related to the dose and/or to the mode of administration.

In the present work rheological characteristics and volumetric oxygen transfer coefficient (kLa) were investigated during batch cultivations of Streptomyces clavuligerus NRRL 3585 for production of clavulanic acid. The experimental rheological data could be adequately described in terms of the power law model and logistic equation. Significant changes in the rheological parameters consistency index (K) and flow behavior index (n) were observed with the fermentation evolution. Interesting correlations between the consistency index (K)/biomass concentration (C X) and the flow behavior index (n)/biomass concentration were proposed. Volumetric oxygen mass transfer coefficient (kLa) was determined by the gas balance method. Classical correlation relating the volumetric oxygen mass transfer coefficient to the operating conditions, physical and to transport properties, including apparent viscosity (muap), could be applied to the experimental results.