Super-magnets, materials whose strong magnetic activity is an attractive differential for the high-tech industry, may have their magnetic performance affected by small variations in their chemical composition. For example, the neodymium and praseodymium content can change the physicochemical properties of the permanent magnets. Aiming at a strict chemical quality control, this work developed an analytical method to quantify the major elements in the materials involved in the production process of didymium (the mixture of neodymium and praseodymium) super-magnets. The simultaneous determination of Nd (401.225 nm), Pr (414.311 nm), Fe (259.837 nm) and B (249.678 nm) in three different sample types (didymium oxide, metallic didymium and (Nd,Pr)-Fe-B alloy) was performed by sample dissolution in acidic media, followed by instrumental measurements using an Inductively Coupled Plasma Optical Emission Spectrometer. Linear calibration curves were obtained with high coefficient of determination (0.9983 ≤ R2 ≤ 0.9999) and with appropriate limits for determining these elements at the percentage level, reaching detection limits less than 0.07 cg g-1. The precision of the method was improved by weighing of the solutions during all the dilution steps and was evaluated by the coefficient of variation associated to instrumental precision (0.3 – 0.7%), method intermediate precision (1.9 – 3.1%) and also by the typical mass fraction provided as uncertainty (0.04 – 0.20 cg g-1), reaching the pressing need to distinguish the content of the rare earth elements in less than 1 cg g-1. The accuracy of the method was assessed by spiked and recovery test (96-104% for spikes equal to or greater than 0.50 cg g-1) and also by the use of different analytical methods, involving the participation of other laboratories, obtaining an acceptable degree of agreement (85 – 107%).
Dust is recognized as a route of exposure to environmental pollutants. The city of Limeira, Sao Paulo state, Brazil, is a production center for jewelry and fashion jewelry, where part of this jewelry production is home-based, informal, and outsourced. The aim of this study was to evaluate exposure to Potentially Toxic Elements (PTE: Cr, Sn, Mn, Sb, Ni, Cu, Zn, Cd, Pb, and As) in dust among children from households of informal workers using electrostatic dust cloths (EDC). Dust samples were collected in 21 exposed and 23 control families using EDC from surfaces where dust deposits had accumulated for approximately 14 days. In exposed families, dust samples were also collected from welders’ workstations. PTE concentrations were then determined using inductively coupled mass spectrometry (ICP-MS). The results raised concerns in relation to Cr, As, and Cd exposure among children within the informal home-based production environment. Blood PTE concentrations in children showed a moderate correlation with levels of Cr (Rho 0.40), Zn (Rho −0.43), and As (Rho 0.40), and a strong correlation with Cd (Rho 0.80) (p < 0.05), detected in dust. In conclusion, analyzing dust collected using EDC proved a potentially low-cost tool for determining PTE in dust. In addition, the results confirmed that informal home-based work poses a risk for children residing in these households. Public policies are needed to assist these families and promote better conditions of occupational health and safety for the whole family.
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