Proposição de métodos analíticos utilizando decomposição ácida e solubilização alcalina para determinação multielementar em amostras de méis e açúcares por técnicas empregando plasma indutivamente acoplado

Abstract

Honey and sugars contain carbohydrates and minerals and are widely consumed by the population. Due to daily consumption, generally in quantities exceeding 50 g, as recommended by the World Health Organization (WHO), it is necessary to evaluate the quality of these food products. This Doctoral Thesis aimed to propose analytical methods for the determination of inorganic constituents in honey and sugar samples using inductively coupled plasma (ICP) techniques. Firstly, a 2⁴⁻¹ fractional factorial design was applied to optimize the preparation of honey and sugar samples using a closed digestion block. The optimized condition involved the digestion of approximately 0.25 g of honey or sugar sample with the addition of 2.0 mol L⁻¹ HNO₃ and 3.0% m m-1 H₂O₂, in a reaction volume of 5.0 mL, heated to 180 °C for 120 minutes. The analytical method allowed the quantification of Al, As, Ba, Ca, Cd, Co, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Se, Sn, and Zn using inductively coupled plasma optical emission spectrometry (ICP OES). The limits of quantification (LOQ) values ranged from 0.01 (Ba) to 35 (S) mg kg⁻¹. The accuracy of the analytical method was confirmed through the analysis of certified reference materials (CRMs) of tomato leaves (CRM-Agro 1003a) and sugarcane leaves (CRM-Agro 1005a), obtaining a precision expressed as relative standard deviation (%RSD) of less than 11% (n=3) for all analytes. Forty-seven samples of honey (22) and sugars (25) were analyzed and the analytical method showed simplicity, accuracy, precision and a favorable environmental profile with the Green Chemistry concept (AGREE: 0.57). Essential and potentially toxic elements (EPTE) were determined in honeys and sugars by inductively coupled plasma mass spectrometry with triple quadrupole (ICP-MS/MS), with LOQ values between 0.002 (Cd) and 1.4 (Zn) mg kg⁻¹. Precision and accuracy were evaluated through analysis of CRMs from tomato leaves (CRM-Agro 1003a) and sugarcane leaves (CRM-Agro 1005a), showing good quantitative analysis. The concentrations were determined by ICP-MS/MS and the health risk for adults was estimated by the total target risk quotient (TTHQ), obtaining a value of 1.11 × 10⁻⁴ for honey and 8.24 × 10⁻¹ for sugar, indicating the absence of significant risk for non-carcinogenic effects from the ingestion of these foods containing EEPT. The second study developed an analytical method employing alkaline solubilization with tetramethylammonium hydroxide (TMAH) assisted by ultrasonic energy to determine the concentrations of Al, Ba, Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn in honey samples by ICP OES. A full 2³ factorial design was applied, and the chosen variables were: TMAH volume (100-500 µL at 25% m v-1 in methanol), thermostatic heating (40°C and 80°C), and sonication time (10-40 min). The best established condition employed approximately 0.25 g of honey sample, with the addition of 100 µL of TMAH, made up to 3 mL with deionized water, applying thermostatic heating at 80°C and a sonication time of 10 minutes. Afterwards, the resulting solution was made up to a volume of 10 mL with deionized water and analyzed by ICP OES. The analytical method showed good accuracy (recoveries between 88.0% and 107.5%) and precision (%RSD ≤ 4.6%), being applied to 22 honey samples collected in Bahia. The second analytical method was efficient, fast, reliable, and environmentally friendly, obtaining an AGREE rating of 0.73. Therefore, in this work, the different analytical methods developed were reliable and efficient, and can contribute to quality control of honeys and sugars in routine chemical analyses, considering that there are no standardized methods for quantitative analysis currently available.