66 -- LOW TEMPERATURE ASHER

MINE SAFETY AND HEALTH ADMINISTRATION IS SEEKING VENDORS THAT CAN SUPPLY THE REQUESTED ASHER DESCRIBED BELOW. Low Temperature Ashers Metal-Nonmetal respirable dust samples are collected on PVC membrane filters. The samples cannot be directly analyzed for silica on the filter used for collecting the samples; the filter matrix must be destroyed and the dust must be redeposited onto membrane filters with more desirable analytical properties. Metal-Nonmetal samples to be analyzed by x-ray diffraction can be ashed in a hot muffle as an alternative to low temperature ashing. If ashing in a hot muffle is used the dust samples would have to be treated with hydrochloric acid to remove calcite, which might otherwise react with quartz and thus result in a negative bias in the quartz analysis. Four chamber low temperature radio frequency ashers are used to prepare MNM samples for silica analysis at the PSHTC laboratory. The systems employ radio-frequency induced oxygen plasmas operating at .001 atmosphere pressure to decompose the samples at a temperature of approximately 250 Co. Each asher consists a vacuum system, a radio frequency generator, an oven compartment containing the RF coils and chambers, a matching network of tuning capacitors to balance the RF load, and a controller for RF forward power, oxygen flow, and cycle time. A two hour ashing cycle is required to oxidize the air filter and the organic carbon components for each set of 20 samples. Because of the chemical pretreatment required, the use of alternative techniques is not feasible for processing 8,000 enforcement samples per year. ALL VENDORS THAT MEET AND CAN SUPPLY THIS REQUIREMENT PLEASE SEND YOUR INFORMATION ELECTRONICALLY TO [email protected], [email protected] OR FAX A COPY TO (304) 256-3332. NO TELEPHONE REQUEST WILL BE ACCEPTED.