Biomedical subjects

J Ruana

Publications and source records attributed to J Ruana.

4 recordsLinked to original sources

PubMed2003

Biofilm structure and function and possible implications for riverine DOC dynamics.

Biofilms are major sites of carbon cycling in streams and rivers. Here we elucidate the relationship between biofilm structure and function and river DOC dynamics. Metabolism (extracellular enzymatic activity) and structure (algae, bacteria, C/N content) of light-grown (in an open channel) and dark-grown (in a dark pipe) biofilms were studied over a year, and variations in dissolved organic carbon (DOC) and biodegradable DOC (BDOC) were also recorded. A laboratory experiment on 14C-glucose uptake and DOC dynamics was also performed by incubating natural biofilms in microcosms. On the basis of our field (annual DOC budget) and laboratory results, we conclude that light-grown biofilm is, on annual average, a net DOC consumer. This biofilm showed a high monthly variability in DOC uptake/release rates, but, on average, the annual uptake rate was greater than that of the dark-grown biofilm. The higher algal biomass and greater structure of the light-grown biofilm may enhance the development of the bacterial community (bacterial biomass and activity) and microbial heterotrophic activity. In addition, the light-grown biofilm may promote abiotic adsorption because of the development of a polysaccharide matrix. In contrast, the dark-grown biofilm is highly dependent on the amount and quality of organic matter that enters the system and is more efficient in the uptake of labile molecules (higher 14C-glucose uptake rate per mgC). The positive relationships between the extracellular enzymatic activity of biofilm and DOC and BDOC content in flowing water indicate that biofilm metabolism contributes to DOC dynamics in fluvial systems. Our results show that short-term fluvial DOC dynamics is mainly due to the use and recycling of the more labile molecules. At the river ecosystem level, the potential surface area for biofilm formation and the quantity and quality of available organic carbon might determine the effects of biofilm function on DOC dynamics.

Analysis of Variance↗

PubMed1998

Capillary zone electrophoresis with indirect UV detection of haloacetic acids in water.

A capillary zone electrophoresis (CZE) system for determining haloacetic acids in water was optimized with indirect photometric detection. Two different carrier electrolytes, potassium hydrogenphthalate and sodium 2,6-naphthalenedicarboxylate, were evaluated in terms of sensitivity and two different electroosmotic flow modifiers, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide, were tested. Parameters such as electrolyte concentration and pH, and the concentration of the electroosmotic flow modifiers, which affect the CZE separations, were investigated. The method was used to determine haloacetic acids in chlorine tap water using the liquid-liquid extraction process.

Acetates↗

PubMed1997

Application of solid-phase extraction discs with a glass fiber matrix to fast determination of polycyclic aromatic hydrocarbons in water.

The extraction of polycyclic aromatic hydrocarbons (PAHs) in water with solid-phase extraction (SPE) discs on a glass fiber matrix has been less studied than other systems such as SPE column extraction or the carbofluor matrix discs. In this paper we have studied SPE discs with a glass fiber matrix (SPE disc GFM) to extract PAHs from aqueous samples, which have then been separated and detected with high-performance liquid chromatography-fluorescence detection. We have found that the proposed method of analysis allows us to obtain detection limits of 0.1 ng/l for benzo[a]pyrene and a variation of 6% in the recovery of said compound at the level of 1 ng/l, and it complies with the required specifications for PAHs in the EU Directive draft on drinking water. The use of GFM discs allows us to shorten the extraction times of PAHs by between 3 and 12 times in comparison with other SPE systems. They can concentrate volume samples of up to 1 l, with PAH recoveries at the level of 1-2 ng/l higher than 80 +/- 10% and detection limits of between 0.1-2 ng/l, depending on the compound studied.

1-Propanol↗

PubMed1993

Determination of phenols at the ng/1 level in drinking and river waters by liquid chromatography with UV and electrochemical detection.

Solid-liquid extraction of samples and liquid chromatography with UV and electrochemical detection with laboratory-made microcolumns were applied to the separation and identification of phenols and substituted phenols in waters. The compounds mainly studied were the eleven phenols considered as priority pollutants by the US Environmental Protection Agency. Chromatographic separation was carried out with several water-methanol isocratic mobile phases; use of the autoincrement mode of the electrochemical detector allowed the compounds in the samples to be confirmed. The chromatographic system worked automatically. The detection limits obtained with prior concentration of the samples were 40-600 ng/l, depending of the phenol. Electrochemical detection was used for the determination of phenols in river and drinking waters; phenols at the ng/l level was detected.

Chromatography, Liquid↗