retained by the filter disc. To test this conclusion three solutions 

 containing Cs^-^^ were used. The first contained 100 ml of distilled water, 

 the second, 100 ml of millipore-f iltered sea water, and the third, 105 ml 

 of millipore-f iltered culture media (100 ml sea water, 5 ml enrichment medium). 

 Triplicate ten ml aliquots were withdrawn from each flask and were filtered 

 through HA type millipore filter pads. 



In a further attempt to reduce the radioisotope adsorption Millipore 

 filter pads were prewashed with an EDTA* solution or a hydrofluoric acid 

 solution. For this purpose a one per cent solution of hydrofluoric acid or 

 an EDTA* (25 mg/L) solution was used. 



Following is a tabulation of the results obtained in the study. 

 Table 1 



Distilled water with 

 Cs-Bal37 added 

 9,140 counts per ml. 



Sea water-millipore fil- 

 tered with Cs-Bal37 

 added 

 18,685 counts per ml. 



Culture media-millipore 



filtered with Cs-Bal37 



added 



12,755 counts per ml. 



No 

 prewash 



HF (1%) 

 prewash 



EDTA 



prewash 



No 

 prewash 



HF (1%) 

 prewash 



EDTA 

 prewash 



No 

 prewash 



HF (17o) 

 prewash 



EDTA 



prewash 



c.p ,m. 

 retained 

 on ml- 

 lipore 

 filter 

 pads . 



173 

 147 

 242 



156 

 140 



136 

 181 

 279* 



57 

 56 

 70 



100 



48 

 58 



45 

 54 

 37 



121 

 23 

 17 



38 

 38 



41 



45 

 80 

 48 



** Two washes with EDTA solution and two rinses with distilled water. 

 * Ethylene diamine tetraacetic acid 



From these results it can be seen that Millipore filter discs do retain: 

 varying amounts of the isotope, and that prewashing does not appreciably reduce 

 the retention of the isotope. 



The amount of adsorption of Cs-137 onto glassware was also checked. In 

 this experiment, 125 ml Pyrex brand Erlenmeyer flasks were used. To insure 

 cleanliness of the glassware, the flasks were washed, rinsed 6 times with tap 



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