Rapid and sensitive method for the determination of acetaldehyde in fuel ethanol by high-performance liquid chromatography with UV-Vis detection

A high-performance liquid chromatography (HPLC) method for the determination of acetaldehyde in fuel ethanol was developed. Acetaldehyde was derivatized with 0.900 mL 2,4-dinitrophenylhydrazine (DNPHi) reagent and 50 mu L phosphoric acid 1 mol L-1 at a controlled room temperature of 15 degrees C for 20 min. The separation of acetaldehyde- DNPH (ADNPH) was carried out on a Shimadzu Shim-pack C-18 column, using methanol/LiCl(aq) 1.0 mM (80/20, v/v) as a mobile phase under isocratic elution and UV-Vis detection at 365 nm. The standard curve of ADNPH was linear in the range 3-300 amg L-1 per injection (20 mu L) and the limit of detection (LOD) for acetaldehyde was 2.03 mu g L-1, with a correlation coefficient greater than 0.999 and a precision (relative standard deviation, RSD) of 5.6% (n=5). Recovery studies were performed by fortifying fuel samples with acetaldehyde at various concentrations and the results were in the range 98.7-102%, with a coefficient of variation (CV) from 0.2% to 7.2%. Several fuel samples collected from various gas stations were analyzed and the method was successfully applied to the analysis of acetaldehyde in fuel ethanol samples.

GC analysis of organotin compounds using pulsed flame photometric detection and conventional flame photometric detection

Organotin compounds, largely used as biocides in antifouling paints, are among the most toxic materials introduced into the aquatic environment. Sensitive analytical methods are thus required to characterize their occurrence in environmental and biological matrices. The comparison between two different photometric detectors in terms of analytical performance was carried out for the analysis of organotin compounds. A flame photometric detector (FPD) and a pulsed flame photometric detector (PFPD) were optimized. Their respective sensitivity, linearity range and selectivity were evaluated. Limits of detection obtained for a tributyltin compound (TBT) were 5.0 and 0.9 pg (as Sn) for the FPD and PFPD, respectively, using a 390 nm filter. The PFPD showed higher selectivity, besides reduced gas consumption in the flame, and is very attractive for organotin compound speciation in complex environmental matrices.

Determination of rice herbicides, their transformation products and clofibric acid using on-line solid-phase extraction followed by liquid chromatography with diode array and atmospheric pressure chemical ionization mass spectrometric detection

A simultaneous method for the trace determination of acidic, neutral herbicides and their transformation products in estuarine waters has been developed through an on-line solid-phase extraction method followed by liquid chromatography with diode array and mass spectrometric detection. An atmospheric pressure chemical ionization (APCI) interface was used in the negative ionization mode after optimization of the main APCI parameters. Limits of detection ranged from 0.1 to 0.02 ng/ml for 50 mi of acidified estuarine waters preconcentrated into polymeric precolumns and using time-scheduled selected ion monitoring mode. Two degradation products of the acidic herbicides (4-chloro-2-methylphenol and 2,4-dichlorophenol) did not show good signal response using APCI-MS at the concentration studied due to the higher fragmentor voltage needed for their determination For molinate and the major degradation product of propanil, 3,4-dichloroaniline, positive ion mode was needed for APCI-MS detection. The proposed method was applied to the determination of herbicides in drainage waters from rice fields of the Delta del Ebro (Spain). During the S-month monitoring of the herbicides, 8-hydroxybentazone and 4-chloro-2-methylphenoxyacetic acid were successively found in those samples. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Trypanosoma vivax infection dynamics in a cattle herd maintained in a transition area between Pantanal lowlands and highlands of Mato Grosso do Sul, Brazil

Trypanosoma vivax outbreaks in beef cattle in the Pantanal region of Mato Grosso do Sul state, Brazil, causes relevant economical impact due to weight loss, abortion and mortality. Cattle moved from the Pantanal to adjacent areas of this ecosystem for breeding and fattening is a common feature. Therefore an epidemiological study on breeding cows in the transition area between Pantanal lowland and adjacent highlands of Mato Grosso do Sul was performed to determine the T. vivax infection dynamics and outbreak risk. Three experimental groups were formed: Group 1 consisted of cows parasitologically negative by the Woo test and in the enzyme-linked immunosorbent assay for T. vivax antibody detection (Tv-ELISA-Ab); Group 2 parasitologically negative and positive in the Tv-ELISA-Ab; and in Group 3 cows were parasitologically positive and with positive reactions in the Tv-ELISA-Ab. During 24 months, the cows' dislodgment between the above established groups was monitored by Woo test and Tv-ELISA-Ab exams. The tabanid population was also monitored and the highest number occurred during the rainy season. Although parasitemias were detected only in the first four samplings of the experimental period, the cows could be considered as trypanotolerant, because no clinical signs were observed. Despite the higher T. vivax incidence during the dry season, no disease symptoms were seen. Even though T. vivax epidemiological situation in the herd was characterized as endemic with seasonal variation, the probability of outbreaks was null within the conditions of the study.

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)

On-line redox speciation analysis of antimony using L-proline immobilized on controlled pore glass and hydride generation inductively coupled plasma optical emission spectrometry for detection

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

DETECTION of MOGIBACTERIUM TIMIDUM IN SUBGINGIVAL BIOFILM of AGGRESSIVE and NONDIABETIC and DIABETIC CHRONIC PERIODONTITIS PATIENTS

The aim of the present study was to evaluate the frequency of detection of Mogibacterium timidum in subgingival samples of subjects with generalized aggressive periodontitis (GAgP) and uncontrolled diabetic and non-diabetic subjects with generalized chronic periodontitis (GChP). 48 patients with GAgP, 50 nondiabetic and 39 uncontrolled (glycated hemoglobin >7%) type 2 diabetic subjects with GChP were enrolled in this study. Subgingival biofilm were collected from deep pockets (probing depth > 7 mm). After DNA extraction, M. timidum was detected by Nested Polymerase Chain Reaction and chi-square test was used to data analysis (p>0.05). There were no differences in the frequency of detection of M. timidum between subjects with GAgP (35%) and non-diabetic subjects with GChP (40%) (p>0.05). The frequency of detection of M. timidum was significantly higher in deep pockets of diabetic subjects with GChP (56%) when compared to GAgP (p<0.05), but similar to non-diabetic subjects with GChP (p>0.05). The frequency of detection of M. timidum was higher in subjects GChP presenting uncontrolled type 2 diabetes mellitus, when compared to GAgP subjects.

Well-conditioned robust observer for detection of faulty systems components

A new concept of fault detection and isolation using robust observation for systems with random noises is presented. The method selects the parameters from components that may fault during the process and constructs well conditioned robust observers, considering sensors faults. To isolate component failures via robust observation, a bank of detection observers is constructed, where each observer is only sensitive to one specified component failure while robust to all other component failures.

Secretion of middle ear in infants - Occurrence, recurrence and related factors

Objective: The present study aimed at evaluating the occurrence and recurrence of middle ear effusion and possible associated factors in the first two years of life of 190 newborns and infants, participants in the interdisciplinary prevention, detection, and intervention program at the Clínica de Educação para Saúde of Universidade do Sagrado Coração, Methods: Newborns and infants were monthly submitted to anamneses, otoscopy, behavioral hearing assessment using sound instruments and pure tones (pediatric audiometry) and tympanometry. Results: The results revealed that 68.4% of infants presented one or more episodes of middle ear effusion during their two first years, with more recurrence among males. Peak occurrence was between four and 12 months of age and, the earlier the first episode, the higher the probability of recurrence. Greatest incidence was during May and August. It was found that, of the variables investigated, the period of exclusive breastfeeding actuated as a protector factor. With respect of risk factors, it was observed that passive smoking, gastro-esophageal reflux and respiratory allergy were related with the recurrences of effusion. Conclusion: Findings revealed the importance of periodic auditory follow-up for infants during their first two years of life, considered to be the critical period of auditory system maturation, during which sensory deprivation can be responsible for damage to the development of speech, language and other auditory abilities. Copyright © 2005 by Sociedade Brasileira de Pediatria.

An optimised electrochemical biosensor for the label-free detection of C-reactive protein in blood

C-reactive protein (CRP) is an acute phase protein whose levels are increased in many disorders. There exists, in particular, a great deal of interest in the correlation between blood serum levels and the severity of risk for cardiovascular disease. A sensitive, label-free, non-amplified and reusable electrochemical impedimetric biosensor for the detection of CRP in blood serum was developed herein based on controlled and coverage optimised antibody immobilization on standard polycrystalline gold electrodes. Charge transfer resistance changes were highly target specific, linear with log. CRP. concentration across a 0.5-50. nM range and associated with a limit of detection of 176. pM. Significantly, the detection limits are better than those of current CRP clinical methods and the assays are potentially cheap, relatively automated, reusable, multiplexed and highly portable. The generated interfaces were capable not only of comfortably quantifying CRP across a clinically relevant range of concentrations but also of doing this in whole blood serum with interfaces that were, subsequently, reusable. The importance of optimising receptor layer resistance in maximising assay sensitivity is also detailed. © 2012.

Biomimetic sensor based on 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H- porphyrin iron (III) chloride and MWCNT for selective detection of 2,4-D

Exploitation of the electronic properties of carbon nanotubes for the development of voltammetric and amperometric sensors to monitor analytes of environmental relevance has increased in recent years. This work reports the development of a biomimetic sensor based on a carbon paste modified with 5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin iron (III) chloride (a biomimetic catalyst of the P450 enzyme) and multi-wall carbon nanotubes (MWCNT), for the sensitive and selective detection of the herbicide 2,4- dichlorophenoxyacetic acid (2,4-D). The sensor was evaluated using cyclic voltammetry and amperometry, for electrochemical characterization and quantification purposes, respectively. Amperometric analyses were carried out at -100 mV vs. Ag/AgCl(KClsat), using a 0.1 mol L-1 phosphate buffer solution at pH 6.0 as the support electrolyte. Under these optimized analytical conditions, the sensor showed a linear response between 9.9 × 10-6 and 1.4 × 10-4 mol L-1, a sensitivity of 1.8 × 104 (±429) μA L mol -1, and limits of detection and quantification of 2.1 × 10 -6 and 6.8 × 10-6 mol L-1, respectively. The incorporation of functionalized MWCNT in the carbon paste resulted in a 10-fold increase in the response, compared to that of the biomimetic sensor without MWCNT. In addition, the low applied potential (-100 mV) used to obtain high sensitivity also contributed to the excellent selectivity of the proposed sensor. The viability of the application of this sensor for analysis of soil samples was confirmed by satisfactory recovery values, with a mean of 96% and RSD of 2.1% (n = 3). © 2013 Elsevier B.V.

Development of a Loop-Mediated Isothermal Amplification Method for Detection of Histoplasma capsulatum DNA in Clinical Samples

Improved methods for the detection of Histoplasma capsulatum are needed in regions with limited resources in which the organism is endemic, where delayed diagnosis of progressive disseminated histoplasmosis (PDH) results in high mortality rates. We have investigated the use of a loop-mediated isothermal amplification (LAMP) assay to facilitate rapid inexpensive molecular diagnosis of this disease. Primers for LAMP were designed to amplify the Hcp100 locus of H. capsulatum. The sensitivity and limit of detection were evaluated using DNA extracted from 91 clinical isolates of known geographic subspecies, while the assay specificity was determined using DNA extracted from 50 other fungi and Mycobacterium tuberculosis. Urine specimens (n = 6) collected from HIV-positive individuals with culture- and antigen-proven histoplasmosis were evaluated using the LAMP assay. Specimens from healthy persons (n = 10) without evidence of histoplasmosis were used as assay controls. The Hcp100 LAMP assay was 100% sensitive and specific when tested with DNA extracted from culture isolates. The median limit of detection was <= 6 genomes (range, 1 to 300 genomes) for all except one geographic subspecies. The LAMP assay detected Hcp100 in 67% of antigen-positive urine specimens (4/6 specimens), and results were negative for Hcp100 in all healthy control urine specimens. We have shown that the Hcp100 LAMP assay is a rapid affordable assay that can be used to expedite culture confirmation of H. capsulatum in regions in which PDH is endemic. Further, our results indicate proof of the concept that the assay can be used to detect Histoplasma DNA in urine. Further evaluation of this assay using body fluid samples from a larger patient population is warranted.

Electroanalytical determination of bumetanide employing a biomimetic sensor for detection of doping in sports

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Development and application of a screen-printed electrode modified with MWCNT for the electrocatalytic detection of thiram

Interest in the electronic properties of carbon nanotubes has increased in recent years. These materials can be used in the development of electrochemical sensors for the measurement and monitoring of analytes of environmental interest, such as pharmaceuticals, dyes, and pesticides. This work describes the use of homemade screen-printed electrodes modified with multi-walled carbon nanotubes (MWCNT) for the electrochemical detection of the fungicide thiram. The electrochemical characteristics of the proposed system were evaluated using cyclic voltammetry, with investigation of the electrochemical behavior of the sensor in the presence of the analyte, and estimation of electrochemical parameters including the diffusion coefficient, electron transfer coefficient (α), and number of electrons transferred in the catalytic electro-oxidation. The sensor response was optimized using amperometry. The best sensor performance was obtained in 0.1 mol L-1 phosphate buffer solution at pH 8.0, where a detection limit of 7.9 x 10-6 mol L-1 was achieved. Finally, in order to improve the sensitivity of the sensor, square wave voltammetry (SWV) was used for thiram quantification, instead of amperometry. Using SWV, a response range for thiram from 9.9 x 10-6 to 9.1 x 10-5 mol L-1 was obtained, with a sensitivity of 30948 µA mol L-1, and limits of detection and quantification of 1.6 x 10-6 and 5.4 x 10-6 mol L-1, respectively. The applicability of this efficient new alternative methodology for thiram detection was demonstrated using analyses of enriched soil samples.

Electroanalytical detection of pindolol: comparison of unmodified and reduced graphene oxide modified screen-printed graphite electrodes

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)