Nitric acid dissolution of large mixed cellulose ester filters for beryllium determination

Defense program use of beryllium has resulted in the need for a wide variety of sampling methods to assess the potential for airborne beryllium particulates. One technique employed in field sampling uses large (8 × 10 in.) mixed cellulose ester (MCE) filters in high volume air samplers. Standard methods for the acid digestion and analysis of the large MCE filters cannot be utilized as the increase in filter mass leads to an uncontrolled exothermic reaction (open flames). As this compromises data quality and presents a significant safety hazard, we propose here an alternative method for digesting these large filters to ensure a solution compatible with ICP-AES (inductively coupled plasma-atomic emission spectroscopy) analysis. The method is a modification of well accepted hot plate digestion methods, which avoids the use of the most hazardous acids such as perchloric or hydrofluoric. While only beryllium was investigated, it is likely that other metals on filters could be digested by this method. Filter media were spiked with a variety of beryllium sources to test the digestion, including beryllium solution spikes, beryllium metal, beryllium oxide and beryllium in soil. Recovery of beryllium metal (103%), beryllium in soil (96%) and beryllium solution spikes (93%) were excellent.