Novas estratégias para a determinação de halogênios e enxofre em cabelo e unha

Abstract

Microwave-induced combustion (MIC) as a sample preparation method was evaluated for further halogens and sulfur determination in hair and nail by several determination techniques: ion chromatography with conductivity detection coupled to mass spectrometry (IC-CD-MS), inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma optical emission spectrometry (ICP-OES) and potentiometry with ion selective electrode (ISE). Unlike conventional digestion and extraction methods, proposed MIC sample preparation method resulted in a solution fully compatible with several determination techniques. The low dissolved carbon concentration for digestion of hair (300 mg) and nail (100 mg) and the use of dilute alkaline solutions to absorb the elements (100 mmol L-1 NH4OH for hair digestion and 50 mmol L-1 NH4OH for nail digestion) avoiding additional dilution steps before the measurement. Accuracy was assessed through recovery tests with standard solution addition (50 and 100% of the detected concentration) and recoveries ranged from 94 to 106%. Accuracy was also assessed by recovery tests in solid form considering the nail mixed with a certified reference material - CRM (recoveries ranged from 93 to 106%), and by analyzing a CRM of human hair (agreements from 93 to 103%). Relative standard deviation for repeatability and intermediate precision was lower than 10%. The limits of quantification (LOQs) ranged from 0,7 to 20 µg g-1 for bromine, 13 to 40 µg g-1 for chlorine, 8 to 25 µg g-1 for fluorine, 0,02 to 8 µg g-1 for iodine and 8 to 210 µg g-1 for sulfur in hair; and 0,1 to 60 µg g-1 for bromine, 40 to 120 µg g-1 for chlorine, 20 to 80 µg g-1 for fluorine, 0,03 to 25 µg g-1 for iodine and 25 a 800 µg g-1 for sulfur in nail using IC-CD-MS, ICP-MS, ICP-OES and ISE after MIC. Hair and nail in solid form was also analyzed by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and two calibration strategies were evaluated. Using analytical methods proposed in this thesis, it was possible to observe that the analytes concentration varied in a wide range. Moreover, the proposed strategies in this thesis 23 are excellent tools for further studies involving nutritional, environmental, toxicological assessments, and among others.