Abstract
A method is described for the quantitative analysis of microgram quantities of chrysotile. This method utilizes X-ray diffraction combined with an X-ray absorption correction procedure, based on the use of a silver membrane filter and includes a dispersion technique that eliminates the possibility of chrysotile fiber alterations. It also proposes an appropriate value for the deposition area of the sample on filter, which optimizes the diffractometric response of the analyte. The effectiveness of the absorption correction procedure is verified by preparing samples of chrysotile dispersed in artificial matrices and comparing their diffractometric responses with those of pure chrysotile samples. The validity of the overall method is checked by calculating the mass absorption coefficients of the matrices from the experimental data and comparing them with the theoretical values. The reproducibility of the diffractometric responses of pure chrysotile samples, expressed in terms of variation coefficient, is around 9%. The limit of detection for pure chrysotile is established at 2.2 µg, while chrysotile in matrix always can be detected at levels lower than 1% (w/w) in samples with a total weight of 500 µg. The applicability conditions of the method also are discussed both in the case of bulk and airborne samples. Finally, the interferences which disturb the analytical peaks of chrysotile are studied in detail.