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3 4 When countmn• lpha and beta particle activity ~ a gas-flo <br />proportional counting system, counting at the alpha plateau discriminates agains <br />beta particle activity. whereas counting at the beta plateau is sensitive t <br />alpha particle activity present in the sample. This latter effect should b <br />determined and compensated for during the calibration of the specific instrumen <br />being used. <br />4.0 APPARATUS AND MATERIALS <br />4.1 Gas-flow oroportional counting svstem or <br />4.2 Scintillation detection svstem or <br />4.3 Stainless steel count~ng planchets <br />4.4 Electric hot plate <br />4.5 Drvmg oven <br />4.6 Drving lamp <br />4.7 Glass desiccator <br />4.8 Glassware <br />4.9 Analytical balance <br />5.0 REAGENTS <br />5.1 All chemicals should be of "reagent-grade" or equivalent whenever the <br />are commercially available. <br />5.2 Distill ed or deionized water (Type II) having a resistance valu <br />between 0.5 and 2.0 megaohms (2.0 to 0.5 mhos)/cm at 25 °C. <br />5.3 Nita c acid 1 N: Mix 6.2 mL 16 N HNO <br />distilled water and dilute to 100 mL. <br />6.0 SAMPLE COLLECTION. PRESERVATION. AND HANDLING <br />6.1 All samples must have been collected in <br />considerations discussed in Chapter Nine of this manual. <br />(conc.) with deionized o <br />a manner which addresses the <br />w <br />t <br />0 <br />e <br />t <br />Y <br />e <br />r <br />6.2 It is recommended that samples be preserved at the time of collectio n <br />by addin g enough 1 N HNO , to the sample to bring it to pH 2 (15 mL 1 N HNO , per <br />liter of sample is usually sufficient). If sample s are to be collected without <br />preservation. they should be brought to the laboratory within 5 days and the n <br />prese rued and held in the original container for a minimum of 16 hr befor e <br />analysis or transfer of the sample. <br />9310 - 3 <br />CD-ROM Revision 0 <br />Date Seotember 1986 <br />