Bromine and iodine determination in different legumes by ICP-MS after decomposition by microwave-induced combustion

In this study, a method for bromine and iodine determination in legumes by inductively coupled plasma mass spectrometry (ICP-MS) after digestion by microwave-induced combustion (MIC) was developed. Samples (up to 500 mg) were digested in closed system pressurized with 20 bar of oxygen (8 samples in less than 30 min). Ultrapure water and NH4OH solutions (25, 50 and 100 mmol L-1) were evaluated as absorbing solution. Water and 25 mmol L-1 NH4OH were not suitable for Br and I absorption, while 50 and 100 mmol L-1 NH4OH did not presented statistical difference between the results for both analytes (ANOVA/Tukey test, confidence level of 95%). Recovery tests were performed using standards solution or a reference material of corn bran (NIST 8433) mixed with the sample. Recoveries from 98 to 108% were obtained for Br and I, using 50 mmol L-1 NH4OH. The relative standard deviations were up to 9 and 11% for Br and I, respectively. Limits of quantification of 0.03 for Br and 0.009 mg kg-1 for I were obtained. The proposed method was applied to 7 samples of legumes (beans, lentils and soybeans) produced in Brazil. The results showed a wide variation for Br concentrations (0.423 to 2.49 mg kg-1), whereas for I it was not observed (< 0.009 to 0.012 mg kg-1). In this way, the proposed method is an excellent alternative for Br and I determination in legumes and presents several advantages for the routine analysis.