RESUMO
A new analytical method is reported for the determination of 11 volatile carbonyl compounds isolated at room temperature from the headspace of marine algae. This method is based on the conversion of the carbonyl compounds to their 2,4-dinitrophenylhydrazone derivatives followed by high-performance liquid chromatography analysis. Using this method, 11 carbonyl compounds are detected and identified from the dynamic headspace sampling of 10 species of marine algae. Eight compounds are quantitated and the three remaining are only identified. Under optimized conditions, all carbonyl compounds are separated in 32 min. The detection and quantitation limits of the high-performance liquid chromatography method are, respectively, in the range of 0.26-0.85 ng/g of algae (formaldehyde) to 13.77-45.90 ng/g of algae (E)-2-hexenal. The calibration curves are linear in the concentration range of 2.0-1000 microg/L of solution, corresponding to 0.34-170.00 ng/g of algae. Acetaldehyde and propanal are the most abundant carbonyl compounds identified, with concentrations as high as 980 and 790 ng/g, respectively. The present work, as far as we know, is the first analytical methodology that has been developed to determine low-molecular-weight carbonyl compounds in marine algae. Because many species of marine algae are used as human food, the reported method should be useful to investigators studying the nutritional value as well as oxidative spoilage of fresh and preserved marine algae that is destined for human consumption.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Eucariotos/química , Cetonas/análise , Biologia Marinha , Peso Molecular , Padrões de ReferênciaRESUMO
Brominated phenols 2- and 4-bromophenol (2-BP and 4-BP); 2,4- and 2,6-dibromophenol (2,4-DBP and 2,6-DBP) and 2,4,6-tribromophenol (2,4,6-TBP) have been identified as key flavor compounds found in seafoods. Depending on their concentrations, they were responsible for marine or ocean flavor (shrimp/crab/fish/sea salt-like) or for phenolic/iodine/iodoform-like off-flavor. In this work a new analytical methodology was developed to determine, simultaneously, such bromophenols in fish meats, based on reversed-phased high-performance liquid chromatographic separation (RP-HPLC). The separation of bromophenols was made onto a Lichrospher 100 RP-18 column using water:acetonitrile gradient at a flow rate of 1.0mLmin(-1), using absorbance detection at 286nm, were the 2-BP, 4-BP, 2,4- and 2,6-DBP show significant absorbtivity values and at 297nm for 2,4,6-TBP. They were separated in 20min with a good chromatographic resolution (Rs) for the isomeric compounds: 2- and 4-BP, Rs=1.23; 2,4- and 2,6-DBP, Rs=1.63. The calibration curves were linear in the bromophenols concentration range of 200.0-1000ngmL(-1). Under optimized conditions, the detection limit of the HPLC method was 127ngmL(-1) for 2-BP; 179ngmL(-1) for 4-BP; 89.0ngmL(-1) for 2,4-DBP; 269ngmL(-1) for 2,6-DBP and 232ngmL(-1) for 2,4,6-TBP. This method has been applied in determination of bromophenols, isolated by combined steam distillation-solvent extraction with 2mL of pentane/diethyl ether (6:4), from Brazilian fishes samples, collected on the Atlantic coast of Bahia (13 degrees 01'S and 38 degrees 31'W), Brazil. The concentration range determined were 0.20ngg(-1) (2-BP) to 299ngg(-1) (2,4,6-TBP). The method proposed here is rapid and suitable for simultaneous quantification of simple bromophenols in fish meat. As long as we know, it is the first analytical methodology, using RP-HPLC/UV, which was developed to determine simple bromophenols in fish meat.
RESUMO
Background and Objectives - The objectives of this study were to observe: a) if the association of droperidol and metoprolol to a propofol-alfentanil anesthesia contributes to maintain low blood pressure and heart rate to facilitate septoplasties and turbinectomies; b) if nitrous oxide interacts with this association and c) if recovery from anesthesia is influenced by these drugs. Methods - Eighty patients classifield as ASA physical status I of both sexes were studied. Premedication consisted of midazolam 0.1 mg.Kg-1 intramusculary. Induction of anesthesia was performed with alfentanil 25 ug.Kg-1, propofol 0.8-1.5 mg.Kg-1 and vecuronium -.1 mg.Kg-1, followed by tracheal intubation and mechanical ventilation. The patients were allocated into three groups: Group A (control): anesthesia was maintained with intermittent doses of alfentanil, continuous infusion of propofol and ventilation with 100 per cent oxygen; Group B: droperidol 0.15 mg.Kg-1 and metropolol 0.1 mg.Kg-1 were added to the technique and the administration of alfentanil and propofol were adjusted to maintain hemodynamic parameters similar to those observed in Group A; Group C: received the same technique as in Group B, but ventilation was performed with a N2O/O2 mixture (66-69 per cent/34-31 per cent). Arterial blood pressure was maintained 30 per cent below the control values (minimum of 80mmHg) and heart rate at approximately 60 beats/min. Recovery from anesthesia was evaluated as time required for reflexes and consciousness to retur. Dose requirements of propofol and alfentanil were comparede in the studied groups. Results - There were significant differences between the initial and final values of blood pressure as compared to those observed during the resection of the septum and the use of the scope in turbinectomies and closure in each group. Systolic blood pressure was significantly higher in Group A as compared to the other groups. Heart rete was significantly lower in patients receiving metoprolol and droperidol. There were significant differences in alfentanil and propofolconsumption among the studied groups. Patients receiving droperidol, metoprolol and N2O recovered faster. Conclusions - The addition of droperidol and metoprolol to a propofol-alfentanil technique contributes to reduce blood pressure and heart rate to adequate levels for the performance of septoplasties and turbinectomies and to reduce total consumption of alfentanil and propofol. The association of nitrous oxide further reduces drug consumption and promotes faster recovery
