Desenvolvimento de metodologias analíticas para determinação de Mercúrio total em cosméticos e imunobiológicos (vacinas)

Abstract

In the present work, different analytical strategies were developed for the determination of total mercury in vaccine and cosmetic samples. For vaccine samples, a simple, fast, sensitive method that can be applied in routine analysis was developed based on the direct oxidation of thimerosal (TH), an organic mercury compound, to inorganic mercury through the action of different oxidants, employing cold vapor atomic fluorescence spectrometry (CV AFS) as a detection technique. The direct oxidation of TH to Hg(II) was evaluated against four oxidizing systems: (1) KBr/KBrO3; (2) KMnO4; (3) KI/KIO3 and (4) Na2S/KMnO4 using diluted mineral acids (HCl or HNO3). Only systems (1) and (2) showed quantitative TH oxidation efficiency to Hg(II) (≥ 80%). The influence of organic solvents (formic acid and 2-propanol) was evaluated, and the oxidation efficiency ranged from 102 to 114%. Under optimized conditions, the method showed high sensitivity with a limit of detection (LOD) of 0.02 μg L-1 and proved to be accurate with a relative standard deviation (RSD)  4.59% (n = 10). The absence of the matrix effect was confirmed from the addition and recovery tests applied to the vaccine samples, which were fortified with TH, obtaining recoveries of 80.1 to 106% (system 1) and 92.5 to 101% (system 2) (n = 3). The applicability of the method was evaluated in five vaccine samples with different concentrations of TH, and the results obtained agreed with the microwave-assisted digestion procedure (reference method), thus indicating the accuracy of the proposed method. In the second work, two analytical strategies were applied: microwave-assisted digestion and direct oxidation (bromination reaction) with the aid of antifoams using diluted acid (HCl) to determine TH, phenylmercury (FM) and Hg(II) ( as Hgtotal) in micellar cosmetic samples. For the direct oxidation of organic to inorganic mercury, five defoamers were evaluated: (1) amyl alcohol (AA); (2) isoamyl alcohol (AI); (3) A; (4) B and (5) 204. The oxidation process was quantitative only for antifoams A, B and 204. The efficiency of microwave-assisted digestion was evaluated in micellar cosmetic samples in terms of the magnetic resonance spectra profile (1H NMR) and total dissolved organic carbon content in the original systems and in the respective digested systems. Under optimized conditions, the analytical curves were validated from 0.1 to 2.0 μL (microwave) and 0.5 to 20 μL-1 (direct oxidation). The microwave-assisted digestion method showed LOD of 0.02 μg L-1 and RSD  4.66% (n = 10). For the recovery test, micellar cosmetic samples were fortified with TH, FM and Hg(II) and the results obtained ranged from 95.8 to 112% (TH), 89.9 to 112% (FM) and 91.8 to 113% for Hg(II), respectively. For the direct oxidation method, the LODs were 0.038; 0.043 and 0.045 μg L-1 for antifoams A, B and 204, respectively, with RSD  4.81%. The recoveries obtained were quantitative for the samples evaluated, regardless of the species of mercury used in the fortifications and ranged from 96.3 to 117% (antifoam A); 97.1 to 118% (antifoam B) and 82.3 to 110% (antifoam 204), confirming the accuracy of the proposed method. Finally, the method was applied to three samples of micellar cosmetics and the results agreed with the microwave-assisted digestion procedure (reference method). Both methods presented analytical parameters that allow the determination of Hgtotal at trace levels and proved to be viable for quality control analysis of micellar cosmetics and products used for skincare.