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1.
Food Addit Contam ; 20(6): 519-23, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12881123

RESUMO

A headspace solid-phase micro-extraction (HS-SPME) method for the extraction and determination of residual methanol in artificial sweeteners by capillary gas chromatography with flame ionization detection (GC-FID) is described. A manual SPME holder with an 85- microm polyacrylate fibre was used. The optimized conditions for methanol extraction by SPME were: sample agitation, absorption temperature of 30 degrees C, absorption time of 10 min, desorption time of 2 min and sample volume in the vial of 400.0 micro l. Under these conditions the calibration graphs were linear in the range 2.50-31.60 mg x l(-1), and the precision was good (relative standard deviation 4.9%). The detection limit was 0.40 mg x l(-1); the quantification limit was 2.06 mg x l(-1).


Assuntos
Aspartame/química , Contaminação de Alimentos/análise , Metanol/análise , Bebidas/análise , Cromatografia Gasosa/métodos , Análise de Alimentos/métodos , Humanos
2.
Phys Rev E Stat Nonlin Soft Matter Phys ; 67(1 Pt 2): 016216, 2003 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-12636594

RESUMO

Right triangular billiards are very simple systems that are completely integrable in classical mechanics for acute angle pairs (45 degrees,45 degrees ) and (30 degrees,60 degrees ). In quantum mechanics, the energy level spacing distribution of these billiards are neither Poisson-like nor Wigner-like. We use Bohm's formalism to calculate the trajectories, by numerical methods, for a particle inside these billiards. We use a linear combination of the first three energy states as the initial wave function. We show that a particle can have quasiperiodic or chaotic behavior, depending on its initial position in the billiards.

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