Desenvolvimento de metodologia para determinação de sílica cristalina respirável para particulado de minério brasileiro por difração de raios X

Abstract

In this work was a developed an analysis procedure for crystalline -quartz dust in workplaces using X-ray diffraction as an analytical technique. The procedure developed used the filter redeposition of sampled particulate in a membrane of cellulose mixed acetate by dispersion in deionized water and vacuum filtration. The release of the sampled particulate from PVC membrane was performed by ashing at800 °C in a muffle furnace for one hour. For sample analysis it was developed a qualitative reading which aims to identify samples containing -quartz and a slow quantitative reading with objective to quantify the mass of -quartz in the sample. To the quantitative reading, it was use the weighted least squares method for linear regression of the calibration curve with linearity analysis by the graph of standardizedresiduals and the Student t test to linear correlation factor. A correction routine of the intensities of the diffraction peaks was done by tabulated values related to the transmittance of the sample. The procedure has been validated taking into account the parameters of interest, linearity, accuracy, precision, measurement uncertainty, limits of detection and quantification based on Brazilian and international laws. The obtainedresults showed recuperations above 80% and variation coefficient less than 9% for all samples studied. The maximum expanded relative uncertainty was 18%, the limit of detection was 0,006 mg and the limit of quantification was 0,020 mg. These results led to the approval of all validation parameters tested making the procedure amenably touse in our laboratory.