Determinação de constituintes gasosos atraves de sistemas em fluxo mono e bi-segmentados

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

This work describes some analytical methodologies developed for the determination of gaseous analytes by using the monosegmented flow approach. A volumetric monosegmented flow system (VMFS) was developed to determine 02 and C02 in concentrations higher than 5%(v/v) yielding results with relative precision (rsd) better than 3% and accuracy of 0.1%(v/v). About 30 samples can be processed per hour. The VMFS was applied to the detennination of C02 present in the head space of food packages. Another monosegmented system was developed by employing conductimetric detection (CMFS) and applied to the determination of C02 in gaseous samples in concentration range 100 to 1,000 mL L. In this situation a second order equation for the analytical curve was obtained. Measurements showed good relative precision (rsd <5%) and the accuracy was assessed by comparison with gas chromatography (GC). A mean relative error of 5.6% was observed. A new approach to the flow analysis principle was proposed in which two liquid segments (a bisegmented system, SBFS) were employed to allow gaseous analytes to be determined in range from mL L (ppm(v/v)) to nL L (ppb(v/v)). The SBFS employed spectrophotometric detection in order to determine O2 present in head space of food packages. Results were compared with GC and good accuracy was confirmed. This system can be used for determination of different gaseous analytes suck as NO2, S02, H2S etc, depending only on the selective reagent employed for absorption and/or reaction. The SBFS has been preliminarily evaluated for determination of NO2 in synthetic air .A linear analytical curve was obtained in the range from 24 to 250 nL L. With the spectrophotometric or conductometric systems about 60 samples per hour can be processed.

ASSUNTO(S)

espectrofotometria medidores de fluxo quimica analitica sistemas quimicos

ACESSO AO ARTIGO

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