Biomedical subjects

Eduardo Carasek

Publications and source records attributed to Eduardo Carasek.

5 recordsLinked to original sources

PubMed2006

Fast and sensitive method to determine chloroanisoles in cork using an internally cooled solid-phase microextraction fiber.

A new generation of solid-phase microextraction (SPME) fiber, an internally cooled fiber (cold fiber with polydimethylsiloxane loading) that allows heating the sample matrix and simultaneously cooling the fiber coating, was used to determine 2,4-dichloroanisole, 2,6-dichloroanisole, 2,4,6-trichloroanisole and pentachloroanisole in cork. A comparison between the cold fiber and regular SPME fiber was performed. An automated headspace solid-phase microextraction (HS-SPME) using commercial fibers and an internally cooled SPME fiber (CF-HS-SPME) coupled to gas chromatography-time-of-flight mass spectrometry (GC-TOF-MS) was used. The extraction conditions for both CF-HS-SPME and HS-SPME were optimized using full factorial design and Doehlert matrix. The best extraction conditions for CF-HS-SPME were obtained using 10 min of incubation time, 10 min of extraction time, and sample and fiber temperature of 130 and 10 degrees C, respectively. For HS-SPME, polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber was used with 10 min of incubation time, 75 min of extraction time, 85 degrees C of sample temperature, 8 ml of water was added and agitated at 500 rpm. The quantification limits for the target compounds using CF-HS-SPME procedure were between 0.8 and 1.6 ng g(-1) of cork, while for HS-SPME were between 4 and 6 ng g(-1) of cork. Furthermore, the CF-HS-SPME procedure could be used as a non-destructive method after minor modification of the agitator for the autosampler.

Anisoles↗

PubMed2006

Screening of tropical fruit volatile compounds using solid-phase microextraction (SPME) fibers and internally cooled SPME fiber.

In this study, the optimization and comparison of an internally cooled fiber [cold fiber with polydimethylsiloxane (PDMS) loading] and several commercial solid-phase microextraction (SPME) fibers for the extraction of volatile compounds from tropical fruits were performed. Automated headspace solid-phase microextraction (HS-SPME) using commercial fibers and an internally cooled SPME fiber device coupled to gas chromatography-mass spectrometry (GC-MS) was used to identify the volatile compounds of five tropical fruits. Pulps of yellow passion fruit (Passiflora edulis), cashew (Anacardium occidentale), tamarind (Tamarindus indica L.), acerola (Malphigia glabra L.), and guava (Psidium guajava L.) were sampled. The extraction conditions were optimized using two experimental designs (full factorial design and Doehlert matrix) to analyze the main and secondary effects. The volatile compounds tentatively identified included alcohols, esters, carbonyl compounds, and terpernes. It was found that the cold fiber was the most appropriate fiber for the purpose of extracting volatile compounds from the five fruit pulps studied.

Alcohols↗

PubMed2006

Monitoring the formation of trihalomethanes in the effluents from a shrimp hatchery.

Formation of trihalomethanes (THM) was monitored at the Laboratório de Camarões Marinhos (LCM) from the Universidade Federal de Santa Catarina. THM could be present because chlorinated effluents from disinfection are discharged from the different hatchery rooms. THM quantification was done through an analytical methodology using Purge&Trap coupled with a gas chromatograph equipped with an electron capture detector. Relative standard deviation (RSD), limit of detection (LOD) and limit of quantification (LOQ) for the methodology corresponded to the ranges of 8-17%; 0.01-0.03 microg L(-1) and 0.03-0.08 microg L(-1), respectively. Linear working range was of 0.1-8.0 microg L(-1) for all compounds. Enrichment and recovery method was applied to evaluate possible matrix effects and the results varied from 71.2% to 107.9%. LCM was monitored between August and December, 2004. This study showed that THM did not increase with the increase in postlarvae production and also that the aquatic life and the surrounding environment were not affected.

Animals↗

PubMed2006

Analysis of zinc in biological samples by flame atomic absorption spectrometry: use of addition calibration technique.

The quantification of target analytes in complex matrices requires special calibration approaches to compensate for additional capacity or activity in the matrix samples. The standard addition is one of the most important calibration procedures for quantification of analytes in such matrices. However, this technique requires a great number of reagents and material, and it consumes a considerable amount of time throughout the analysis. In this work, a new calibration procedure to analyze biological samples is proposed. The proposed calibration, called the addition calibration technique, was used for the determination of zinc (Zn) in blood serum and erythrocyte samples. The results obtained were compared with those obtained using conventional calibration techniques (standard addition and standard calibration). The proposed addition calibration was validated by recovery tests using blood samples spiked with Zn. The range of recovery for blood serum and erythrocyte samples were 90-132% and 76-112%, respectively. Statistical studies among results obtained by the addition technique and conventional techniques, using a paired two-tailed Student's t-test and linear regression, demonstrated good agreement among them.

Calibration↗

PubMed2002

A new procedure for solid-phase microextraction using a flow-through system with air segmentation.

Three different procedures for solid-phase microextraction (SPME) of trace organic compounds from liquids were evaluated: simple extraction with magnetic stirring, use of a laboratory-made flow-through extraction cell and a new system based on a laboratory-made flow-through extraction cell in which the sample stream is segmented with air bubbles. In this new procedure, the sample flows through the cell as a regular sequence of small plugs separated by air bubbles instead of in a continuous stream. This new system combines the advantages of SPME, as a simple, fast, sensitive and solvent-free sample concentration/introduction technique, with the advantages of on-line processing of aqueous sample as a less time-consuming, efficient and continuous technique. For testing the new flow-through procedure, a mixture of phthalate esters was used for direct absorption from an aqueous solution with a 100 microm polydimethylsiloxane fiber. The efficiency and precision of the procedure were compared with those of extraction with magnetic stirring and the usual flow-through cell concept. The results indicate better contact of the analytes with the extraction film when the air-segmented flow-through extraction cell is employed.

Journal Article↗