Verificação do método Monier-Williams otimizado na determinação de dióxido de enxofre em sucos de frutas, água de coco e cogumelo em conserva Verification of the optimized Monier-Williams method for determining sulfur dioxide in fruit juices, coconut water and mushroom in conserve

This study aimed at assessing the validation analytical parameters of the optimized Monier-Williams method, such as: limit of quantification (LQ), concentration range, linearity, sensibility, selectivity, precision and accuracy for analyzing sulphur dioxide (SO 2 ). Three samples of cashew juice, six of passion fruit juice, five of grape juice, two of coconut water and six of mushroom in conserve were obtained from retail market. The recovery study was carried out on 10 concentrations of sodium sulphite standard solutions ranging from 5 to 2,675 mg/L, and also adding SO 2 solutions into the samples. The methodology was considered efficient and the linearity parameter was proved in the SO 2 applied concentration interval (from 7 to 2,675 mg/L); the curve equation was y = 1.0647x – 13.8697 (r 2 =0.9979). The recovery rates ranged from 87 to 109 %, LQ of 7 mg/L, with RSD of 7 %. The mean recovery results in spiked test samples showed acceptable levels varying from 81 to 115 %. The concentrations of SO 2 found in fruit juices and coconut water complied with the Brazilian legislation. Three brands of mushroom in conserve revealed values above the established maximum limit of 50 mg/kg.