Spectrometric determination of phenol in aqueous samples using a two phase system with the copolymer L35 and lithium sulphate / Determinação espectrométrica de fenol em amostras aquosas utilizando um sistema aquoso bifásico, constituído pelo copolímero L35 e o sal sulfato de lítio

AUTOR(ES)

Fernanda de Lourdes Souza

DATA DE PUBLICAÇÃO

2008

RESUMO

This work developed a simple and environmentally safe spectrophotometric method for the phenol determination in aqueous samples. The method bases on the reaction of sodium nitroprusside (NP), hydroxylamine hydrochloride (HH) and phenol in alkaline medium resulting in the blue-greenish compound decacianodyferrate ([Fe2(CN)10]10 -). This reaction was accomplished in an aqueous two phase system (ATPS) formed by the triblock copolymer poly-(ethylene oxide)poly(propylene oxide)-poli(oxyde etylene), (EO)11(PO) 16(EO)11, with average molar mass of 1900 g mol-1 (L35), 50% of EO, lithium sulphate and water. The product formed in the reaction is transferred preferentially to the superior phase of ATPS where is concentrated. The phenol quantification is indirectly accomplished through absorbance measure of the reaction product by a spectrophotometer of molecular absorption in the UV/visible area. Several parameters were investigated to obtain the best experimental conditions: agitation time, tie line lengths (TLL), reagents concentration, pH of the medium and the type of electrolyte that forms the ATPS. The parameters that showed the better analytical results were: manual agitation for five minutes, TTL of 43,77% (m/m), NP concentration of 1669,9 mg kg-1, HH concentration of 177,20 mg kg-1, pH = 12,00 and electrolyte that form ATPS of lithium sulphate. Once it was obtained the best analytical parameters the method was applied for the phenol determination in different water samples. These were doped with 0,5000 mg kg-1 of phenol originating quantitative recoveries between 98 to 113%. Under these conditions the range varied from 0,2500 to 2,000 mg kg-1 with lineal correlation coefficient of 0,99948. The variation coefficient was 0,113% for the phenol concentration of 0,5000 mg kg-1 and the detection limit and quantification limit were 0,0426 mg kg-1 and 0,141 mg kg-1 respectively.

ASSUNTO(S)

extraction phenol fenol two-phase aqueous system extração quimica analitica sistema aquoso bifásico

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