DETERMINATION OF SILICON IN AIRBORNE PARTICULATE MATTER BY UV-VISIBLESPECTROPHOTOMETRY

A method for the UV-visible spectrophotometric determination of silico n in airborne particulate matter collected on a filter membrane is des cribed. It comprises a two-step digestion procedure with a mixture of HNO3+HClO4 followed by HF (after removal of the filter) in a PTFE clos ed vessel system, followed by the addition of H3BO3 to remove the inte rference of HF, and the spectrophotometric determination of molybdosil icate blue. The sample pretreatment procedure and instrumental determi nation are carefully optimized. The detection limit of the method was found to be 0.6 mu g Si on each filter. The proposed method is applied to a standard reference material, SRM 1638 (NIST). The results obtain ed by this method are compared with those from direct XRF spectrometri c measurement.