Determination of silicon in airborne particulate matter by UV-visible spectrophotometry

A method for the UV-visible spectrophotometric determination of silicon in airborne particulate matter collected on a filter membrane is described. It comprises a two-step digestion procedure with a mixture of HNO3 + HClO4 followed by HF (after removal of the filter) in a PTFE closed vessel system, followed by the addition of H3BO3 to remove the interference of HF, and the spectrophotometric determination of molybdosilicate blue. The sample pretreatment procedure and instrumental determination are carefully optimized. The detection limit of the method was found to be 0.6 μg Si on each filter. The proposed method is applied to a standard reference material, SRM 1648 (NIST). The results obtained by this method are compared with those from direct XRF spectrometric measurement.