Application of a PLA/PBAT/Graphite sensor obtained by electrospinning on determination of 2,4,6-trichlorophenol.

The widespread use of pesticides requires effective detection and quantification tools to improve monitoring of environmental quality. Electrochemical sensors offer a fast and sensitive response, and can also be optimized by combining several constituents and techniques, including biodegradable materials, being useful in the determination of chemical agents from environmental samples. Here, we produced a polymer-based sensor for 2,4,6-trichlorophenol determination, through electrospinning of poly(lactic acid)/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blend with graphite. The graphite-containing fibres were thermally treated and wetted in mineral oil, thus forming a paste, used as an electrode in the electrochemical sensor. The thermal analysis indicated a disorganization of the polymeric chains between the aromatic carbon chain of the PBAT polymer, resulting in a material with low enthalpy, lower crystallinity and greater thermal degradability after insertion of graphite in polymeric fibres. NIR spectra revealed changes related to the carbonyls of the polymeric ester groups. Cyclic voltammetry and square wave voltammetry techniques were applied to study the electrochemical behaviour of developed sensor. The thermal treatment of graphite-containing fibres increased the adhesion surface in which occurs the adsorption of the analyte on the electrode, which improved the peak current in the electrochemical tests. The PLA/PBAT/Graphite sensor applied to determination of 2,4,6-TCP presented the detection and quantification limits of 7.84 × 10-8 mol L-1 (0.0155 mg L-1) and 2.36 × 10-7 mol L-1 (0.0466 mg L-1) with a linearity response of 1.00 × 10-7 mol L-1 and 2.00 × 10-6 mol L-1 with correlation coefficient of 0.993 (r2).

2,4-Dichlorophenol Shows Estrogenic Endocrine Disruptor Activity by Altering Male Rat Sexual Behavior.

Chlorophenols (CPs) have been extensively used worldwide as a treatment to prevent the growth and proliferation of different microorganisms, mainly in the wood and farm industries. Chlorine has been used for water disinfection, and phenol groups are water contaminants; these two groups can react with each other to form species such as 2,4-dichlorophenol (2,4-DCP). 2,4-DCP is still used as an herbicide in many countries such as Mexico. CPs have been largely analyzed, like bisphenol A, for their probable endocrine-disrupting effects in humans and aquatic animals. We still do not understand whether these endocrine responses can be manifested as an impairment in sexual behavior in rodents. With the present toxicology study, the endocrine-disrupting effects of 2,4-DCP on male sexual behavior were investigated. Sexually naïve male Wistar rats were used to assess the endocrine-disrupting effects of 2,4-DCP. The rats were divided into two groups: one control group and one experimental group that was administered 1.25 mg/day of 2,4-DCP for 45 days. After completing treatment, the male sexual behavior of the rats was evaluated. The results of this investigation demonstrated that 2,4-DCP affected male sexual behavior. A decrease in mount latency, intromission latency, and post ejaculation period compared with the control animals was found.

Development of methods based on low-temperature partitioning (LTP) for monitoring cresols and chlorophenols in sewage sludge, soil, and water in column leaching.

Cresols and chlorophenols are chemical contaminants that are potentially toxic to humans and can be found in sewage sludge. These chemical contaminants can migrate into the sludge-soil-water system when sludge is used as a conditioner for agricultural soils. Thus, the objective of this study was to develop methodologies based on extraction with low-temperature partitioning (LTP) to determine cresols and chlorophenols in sewage sludge, soil, and water. The analysis was performed by gas chromatography coupled with mass spectrometry (GC-MS). The validated methods were applied to monitor cresols and chlorophenols in a column-leaching study of a sludge-soil-water system. Satisfactory results were achieved for selectivity, limit of quantification (LOQ), linearity, accuracy, and precision. In the column leaching study, only 2,4,6-trichlorophenol was quantified in sludge samples after 20 days of the experiment. None of the studied compounds were quantified in soil and leached water samples, due to the degradation promoted by the microorganisms present in the sewage sludge. Finally, validated methods were suitable for monitoring cresols and chlorophenols in the sludge-soil-water system.

Biodegradability of Chlorophenols in Surface Waters from the Urban Area of Buenos Aires.

Biodegradability of 2-Chlorophenol (2-CP), 3-Chlorophenol (3-CP), 4-Chlorophenol (4-CP), 2,4-Dichlorophenol (2,4-DCP) and 2,4,6 Trichlorophenol (2,4,6-TCP) has been tested in surface waters in the urban area of Buenos Aires. Samples were taken from the La Plata River and from the Reconquista and Matanza-Riachuelo basins, with a total amount of 18 sampling points. Water quality was established measuring chemical oxygen demand (COD), biochemical oxygen demand (BOD5), and both Escherichia coli and Enterococcus counts. Biodegradability was carried out by a respirometric method, using a concentration of 20 mg L-1 of chlorophenol, and the surface water as inoculum. Chlorophenols concentration in the same water samples were simultaneously measured by a solid phase microextraction (SPME) procedure followed by gas chromatography-mass spectrometry (GC-MS). 2,4-DCP was the most degradable compound followed by 2,4,6-TCP, 4-CP, 3-CP and 2-CP. Biodegradability showed no correlation with compound concentration. At most sampling points the concentration was below the detection limit for all congeners. Biodegradability does not correlate even with COD, BOD5, or fecal contamination. Biodegradability assays highlighted information about bacterial exposure to contaminants that parameters routinely used for watercourse characterization do not reveal. For this reason, they might be a helpful tool to complete the characterization of a site.

Chemotaxis detection towards chlorophenols using video processing analysis.

To our knowledge, this communication is the first report of chemotaxis towards chlorophenols by any bacteria. We used a recently published method based on the agarose in-plug assay combined with video processing analysis and we also present a new index of bacterial mean speed for these assays.

Avaliação histopatológica de polpas de dentes de cães, submetidas a pulpotomia e tratamento com substâncias à base de PMCC + Furacin / Histopathologic evaluation of pulp tissue of dog teeth subdued to pulpotomy and treatment with CMPC + Furacin materials

No presente trabalho, foi avaliada histologicamente a resposta pulpar de dentes de cães submetidos a pulpotomia e tratamento do remanescente pulpar com misturas de PMCC 3,5:6,5 e 2,5:7,5, associadas ao Furacin, com e sem curativo de demora. Para isso utilizou-se os segundos e terceiros pré-molares superiores e os primeiros, segundos e terceiros pré-molares inferiores, de 12 cães adultos jovens, distribuídos em 4 Grupos: GI - PMCC3,5:6,5 - Furacin com curativo, GII - PMCC 2,5:7,5 - Furacin com curativo, GIII - PMCC 3,5:6,5 - Furacin sem curativo e GIV - PMCC 2,5:7,5 - Furacin sem curativo. Após os períodos experimentais de 7, 45 e 90 dias, os animais foram sacrificados e procedeu-se a confecção de lâminas para a análise histológica. Pela metodologia empregada, encontramos que em todos os grupos, as soluções de PMCC - Furacin mostraram-se irritantes ao tecido conjuntivo pulpar, exibindo morte tecidual, com fenõmeno de fixação, caracterizada pela manutenção apagada das estruturas, sendo maior nos grupos onde se utilizou o curativo de demora de PMCC - Furacin por 5 minutos (GI e GII), .............

In the present study it was performed an histologic evaluation of the response of the pulp tissue of dogs teeth subdued to pulpotomy and treatment of the reminiscent pulp tissue with 3.5:6.5 and 2.5:7.5 CMPC associated to Furacin, with or without dressing. Upper second and third bicuspids and lower first, second and third bicuspids of 12 young adult dogs were used and distributed into 4 groups: GI - 3.5:6.5 CMPC - Furacin with dressing, GII - 2.5:7.5 CMPC - Furacin with dressing, GIII - 3.5:6.5 CMPC - Furacin without dressing and GIV - 2.5:7.5 CMPC - Furacin without dressing. After experimental periods of 7, 45 and 90 days, the subjects were sacrified and the histopathologic analysis was performed. According to the methodology used, we observed that in all groups the CMPC - Furacin solutions were irritative to the pulp connective tissue, showing tissue death, with fixation phenomena characterized by the loss of dye affinity. This finding was higher in the groups in which CMPC - Furacin dressing was used for 5 minutes (GI and GII), when compared to the groups without the dressings....