Determination of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography with electrochemical detection

A new methodology was developed for analysis of aldehydes and ketones in fuel ethanol by high-performance liquid chromatography (HPLC) coupled to electrochemical detection. The electrochemical oxidation of 5-hydroxymetkylfurfural, 2-furfuraldehyde, butyraldehyde, acetone and methyl ethyl ketone derivatized with 2,4-dinitrophenylhydrazine (DNPH) at glassy carbon electrode present a well defined wave at +0.94 V; +0.99 V; +1.29 V; +1.15 V and +1.18 V, respectively which are the basis for its determination on electrochemical defector. The carbonyl compounds derivatized were separated by a reverse-phase column under isocratic conditions with a mobile phase containing a binary mixture of methanol /LiClO4(aq) at a concentration of 1.0 x 10(-3) mol L-1 (80:20 v/v) and a flow-rate of 1.1 mL min(-1). The optimum potential for the electrochemical detection of aldehydes-DNPH and ketones-DNPH was +1.0 V vs. Ag/AgCl. The analytical curve of aldehydes-DNPH and ketones-DNPH presented linearity over the range 5.0 to 400.0 ng mL(-1), with detection limits of 1.7 to 2.0 ng mL(-1) and quantification limits from 5.0 to 6.2 ng mL(-1), using injection volume of 20 mu L. The proposed methodology was simple, low time-consuming (15 min/analysis) and presented analytical recovery higher than 95%.

Determination of organochlorine pesticides and polychlorinated biphenyls residues in municipal solid waste compost by gas chromatography with electron-capture detection

A simple and efficient method for the simultaneous gas chromatographic determination of ten organochlorine pesticides (alpha-HCH, beta-HCH, gamma-HCH, p,p'-DDT, o,p'-DDT, p,p'-DDD, p,p'-DDE, aldrin, endrin, and dieldrin) and six congeners of PCBs (PCB 28, 52, 118, 138, 153, and 180) in municipal solid waste compost is described. The procedure involves a solid-phase dispersion matrix using celite as dispersant sorbent, alumina as clean up sorbent and hexane-dichloromethane (7:3, v/v) mixture as eluting solvent. An additional purification step with copper was necessary to eliminate sulphur. Analysis of the sample was performed by GC-ECD. The method was validated with fortified samples at two concentration levels (0.025 and 0.05 mg kg(-1)). Average recovery ranged from 77 to 121% with relative standard deviation between 1 and 18%. The detection limits, which ranged from 0.003 to 0.01 mg kg-1, were lower than those established by the Baden-Wurttemberg directive (0.033 mg kg(-1)).

A Method for Determination of Ammonia in Air using Oxalic Acid-Impregnated Cellulose Filters and Fluorimetric Detection

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Polysiloxane-poly(propylene oxide) hybrid discs as solid phase in anti-HCV detection using a recombinant core protein

In this work, siloxane-poly(propylene oxide) discs (PPO disc) prepared using the sol-gel process were used as solid phase in enzyme-linked immunosorbent assays (ELISA) for the detection of anti-hepatitis C virus (HCV) antibodies. The HCV RNA from serum (genotype 1b) was submitted to the RT-PCR technique and subsequent amplification of the HCV core 408 pb. This fragment was cloned into expression vector pET42a and expressed in Escherichia coli as recombinant protein with glutathione S-transferase (GST). Cell cultures were grown and induced having a final concentration of 0.4 x 10(-3) mol L-1 of IPTG. After induction, the cells were harvested and the soluble fraction was analyzed using polyacrilamide gel 15% showing a band with an approximate molecular weight of 44 kDa, the expected size for this GST-fused recombinant protein. The recombinant protein was purified and continued by immunological detection using HCV-positive serum and showed no cross-reactivity with positive samples for other infectious diseases. An ELISA was established using 1.25 ng of recombinant protein per PPO disc, a dilution of 1: 10,000 and 1:40 for a peroxidase conjugate and serum, respectively, and solutions of hydrogen peroxide and 3,3',5,5'-tetra-methylbenzidine in a ratio of 1: 1. The proposed methodology was compared with the ELISA conventional polystyrene-plate procedure and the performance of the PPO discs as a matrix for immunodetection gave an easy synthesis, good performance and reproducibility for commercial application. (c) 2007 Elsevier B.V. All rights reserved.

The influence of hydrogen plasma pre-treatment on the structure of BDND electrode surface applied for phenol detection

The surface properties of boron-doped nanocrystalline diamond films treated with H(2) plasma was investigated in regard to their electrochemical response for phenol oxidation. The surface of these films is relatively flat formed by crystallites with sizes of about 40 nm. X-ray photoelectron spectroscopy analyses showed that electrode surface has a high amount of C-H bonds. This behavior is in agreement with Mott-Schottky plot measurements concerning the flat band potential that presented a value as expected for hydrogenated diamond surface. This electrode presented the phenol detection limit of 0.08 mg L(-1) for low phenol concentrations from 40 to 250 mu mol L(-1).

Detection of cytokines and nitric oxide synthase in skin lesions of Jorge Lobo's disease patients

Studies investigating the immunopathological aspects of Jorge Lobo's disease have shown that the inflammatory infiltrate consists mainly of histiocytes and multinucleated giant cells involving numerous yeast-like cells of Lacazia loboi, with the T lymphocytes more common than B lymphocytes and plasma cells. The quantification of cytokines in peripheral blood mononuclear cells culture supernatant has revealed alterations in the cytokines profile, characterized by predominance of a Th2 profile. In view of these findings and of the role of cytokines in cell interactions, the objective of the present study was to investigate the presence of the cytokines IL-10, TGF-ss 1 and TNF-alpha, as well as iNOS enzyme in granulomas induced by L. loboi. Histological sections obtained from skin lesions of 16 patients were analyzed by immunohistochemistry for the presence of these cytokines and iNOS. The results showed that TGF-ss 1 was the cytokine most frequently expressed by cells present in the inflammatory infiltrate, followed by IL-10. There was a minimum to discrete positivity of cells expressing TNF-alpha and iNOS. The results suggest that the presence of immunosuppressive cytokines in skin lesions of patients with the mycosis might be responsible for the lack of containment of the pathogen as demonstrated by the presence of numerous fungi in the granuloma.

A disposable chitosan-modified carbon fiber electrode for dengue virus envelope protein detection

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Evaluation of the microscopic observation drug susceptibility assay for detection of Mycobacterium tuberculosis resistance to pyrazinamide

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Carbamide Peroxide Determination in Tooth Whitening Using a Reagentless HRP-Biosensor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Detection of catechol using mixed Langmuir-Blodgett films of a phospholipid and phthalocyanines as voltammetric sensors

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Detection of Toxoplasma gondii DNA in the milk of naturally infected ewes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)