How Do Three Different Methodologies Used For The Determination Of 226ra?

In this study, three different methodologies have been employed for the determination of 226Ra by means of liquid scintillation technique. The first one (referred to as "Rn-LSC-28" hereafter and the tables and figures) is based on the method of Prichard and Gessel (1977) and Cooper et al. (1988) and also used by Escobar et al. (1996), Zouridakis et al. (2002) and Aleissa et al. (2012). In this procedure, 8 mL of each standard solution was transferred to a high density polyethylene vial, covered with Teflon caps to prevent radon from escape, preloaded with a 12 mL of insoluble high efficiency mineral oil scintillation cocktail (Perkin Elmer) so as to avoid white precipitate formation. Prior to counting for 226Ra, the samples were kept for 28 days in a refrigerator for the equilibrium between 222Rn and 226Ra to take place. During the storage period, precaution was taken to prevent radon release and avoid oxygen-cocktail contact as O2 can destroy the sensitive ingredient in the cocktail. The second method (referred to as "228Ra-LSC" hereafter and the tables and figures) is based on a combined procedure for the determination of 226Ra along with 228Ra and
The calibration with Hidex 300 SL was also performed using the two previously mentioned ways. Using the manufacturer' standard solution, the efficiency achieved was 98 and 73% for alpha and beta counting, respectively. Whereas, using the internal (mixed 214Am-90Sr) standard source the Pulse Length Index (PLI) to discrimination of alpha and beta at 6. The triple-to-double coincidence ratio (TDRC), which the same as the efficiency, was 100% for alpha and 99.75% for beta counting. To set window for counting 226Ra, a standard source of 226Ra activity of 2 Bq mL-1 was made in lab. The net count of total area under window from 550 to 750 with TDCR of 300% was used because this window covers the 222Rn, 218Po and 214Po