T a b l e VI. Se, As, Z n , Cd and Hg C o n t e n t D e t e r m i n e d in t h e Proposed S t a n d a r d Reference Material, Residual Fuel Oila Sample
1 2
se
0.137 0.141 0.139 0.144 (H) 0 . 1 2 9 (L)
As
Zn
0 . 1 0 5 (H) 0.095 0,095 0 . 0 8 9 (L) 0.098
+ 0.06 0 . 0 9 5 i O.OO* All elemental values expressed in r g / g . * Errors are the standard deviation. Average*
0.138
associated with the determination of each element must be considered. Mercury. T h e 77-keV'gamma ray of mercury-197 was used for the determination. No significant interference from other elements was noted after bromine decontamination. Selenium. The 265-keV gamma ray of selenium-75 was used for the determination, as the 136-keV gamma ray photopeak suffers from interferences from mercury-l97m. After a ten-day decay, the 136-keV gamma photopeak may be used. Zinc. Both the 439-keV gamma ray from zinc-69m and the 1115keV gamma ray from zinc-65 were used for zinc evaluation. Though the sensitivity is about tenfold higher using the 439-keV gamma ray, for all the samples actually examined, t h e 1115-keV gamma ray photopeak from zinc-65 was adequate to evaluate the zinc content. Cadmium. T h e 335-keV gamma ray photopeak of indium-115m in equilibrium with cadmium-115 was used for the determination. This increases about tenfold the sensitivity for cadmium with respect to the use of 530-keV peak of cadmium-115. Arsenic. The 657-keV gamma ray photopeak from arsenic-76 was used. Though the sensitivity is about five times higher using the 559-keV gamma ray photopeak, residual bromine suggested the use of the interference free gamma ray photopeak.
Cd
0.18 0 . 1 5 (L) 0 . 1 9 (H) 0.16 0.18
lO.01
0.17 rt 0 . 0 2
