Desenvolvimento de método para determinação de halogênios e enxofre em chás em única análise

Abstract

In this study, microwave initiated combustion (Microwave Induced Combustion MIC) was evaluated as a sample preparation method for various types of teas (black tea, green tea, lemon balm, boldo and mint) aiming to, subsequently, the determination of fluorine, chlorine, bromine, iodine, and sulfur by ion chromatography (IC). Some parameters were evaluated, such as the sample mass and the absorbing solution (ultrapure water and N H 4 OH 25, 50, 100 and 150 mmol L 1 ), taking into account the analytes and the determination technique used. The maximum sample mass possible to be decomposed was 900 mg, in the form of tablets, and the absorbing solution chosen (through recovery tests) was NH 4 OH 100 mmol L 1 , which provided adequate stabilization of the analytes. A certified reference material was analyzed to evaluate the accuracy of the proposed method. Adequate recoveries (Br and I) and agreements (Cl, F and S) (101 to 107%) wer e obtained for all analytes. The proposed method was applied to tea samples and their concentrations varied in a range from 549 mg kg 1 to 2549 mg kg 1 for chlorine, for sulfur from 786 mg kg 1 to 4023 mg kg 1 , from 223 mg kg 1 to 828 mg kg 1 for fluorine , while bromine and iodine concentrations were below the limits of quantification (42 mg kg 1 , 80 mg kg 1 , respectively) for the analysis of different types of teas.