Emprego de diferentes estrategias para analises em larga escala : screening, extração ultra-sonica e pre-concentração por ponto nuvem

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

This thesis proposes three different procedures to simplify chemical analyses, mostly minimizing time and costs. In the first part, it was developed a screening system to detection of phenothiazines in human urine. A spectrophotometric method based on the reaction of the drugs with K3Fe(CN)6 in acid medium was proposed. The flow system was optimized and the analytical characteristics of the method were determined using a mixture composed by chlorpromazine, methotrimeprazine and promethazine. The cut-off level was established as 2 mmol L and to check the reliability of the proposed screening system, 250 samples containing different concentrations (0.5; 1.0; 1.5; 2.5; 3.0 and 4.0 mmol L) were analyzed. Six percent of false positives (in 1.5 mmol L) and 10% of false negatives (in 2.5 mmol L) were obtained. In the second part of this thesis, it was developed two methods involving ultrasonic bath: an optimization of the conditions to maximize the cavitation and another to acid extraction for Ca, Fe, Mg, Mn and Zn determination in plants. The most important variables in the cavitation were: bath volume water (1L) and vertical (0 cm from the bottom) and horizontal (central) positions of the reaction tube. In the optimized conditions of extraction (0.14 mol L HNO3, 10 min of sonication and particle sizes <75 mm) recoveries of ca.100 % were obtained for Ca, Mg, Mn and Zn. In the last part of this thesis two methods were developed for Co preconcentration using cloud point formed with the mixture of anionic and non-ionic surfactants. In the first, phase s separation were induced adding HCI, and in the second, NaCI. The conditions for complexation (3.5 X 10-4 % m/v 5-Br-PADAP, pH=9,0) and phases separation (4 mol L HCI, 0.1 % m/v Triton X-100 and 0.75 % m/v SDS 1 method and 10 % m/v NaCI, 0.25 % m/v Triton X-100 and 0.1 % m/v SDS 2nd method) were optimized. The preconcentration factors 28.5 and 21.7 for HCI and NaCI methods respectively were obtained. The last was used to the analysis of medicine with good agreement with those results optained by ETAAS.

ASSUNTO(S)

espectroscopia de absorção atomica quimica analitica espectrofotometria solução (quimica)

ACESSO AO ARTIGO

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