ULTIMA Gold uLLT - For Ultra Low Level Counting

ULTIMA Gold uLLT for ultra low level counting
Overview
ULTIMA Gold™ uLLT is perfect for ultra low level LSC applications using QUANTULUS® or Tri-Carbs in low level mode. The
ultra low background, high efficiency and good sample uptake
is optimal for environmental monitoring applications. Of course,
all counting conditions have to be optimized for best results.
Ultra low backgrounds
Most industrial raw materials that are used for LSC cocktail
production are manufactured with potassium catalysts.
Potassium is always contaminated with a trace amount of
naturally radioactive 40K (0.0119%). This natural isotope may
Figure 1: QUANTULUS spectra for different lots of UG-LLT and UG-uLLT
result in increased background values in the higher energy
channels. This effect is observed in the QUANTULUS spectrum
shown in Figure 1 below; the peak in the 600 – 900 energy
channel for the red and blue graph are caused by 40K contamination of the cocktail, the other graphs are for different lots of
ULTIMA Gold uLLT, produced with potassium free raw materials.
A high background in the 600 – 900 channel can mask low
levels of Yttrium-90 or Strontium-90.
Another source of background is caused by chemiluminescent effects; short bursts of light with low energy as result of
chemical reactions. This effect can be seen in the low energy
channels of QUANTULUS (0 – 200; random). To produce a
good ultra low level cocktail it is important to guarantee low
background levels in these channels by reducing chemiluminescence to avoid masking low tritium levels (3H). As can be
seen in the table below UG-uLLT has a 10-15% lower randomsignal than UG-LLT and a much lower 40K signal as UG-LLT.
In Tri-Carb® this better performance is also detected. The
table below shows background levels in 3 energy windows
(A=low energy, B=mid-energy, C=high energy channel) for
ULTIMA Gold LLT and ULTIMA Gold uLLT. The percentage
of luminescence is also given in the last column. A good
performance is seen across the spectrum for UG-uLLT.
Table 1. Background levels in QUANTULUS for UG-LLT and UG-uLLT.
LSC Cocktail
Random
Tritium
Net tritium
40K
SQPE
ULTIMA Gold LLT
0.135
1.097
0.962
8.546
918
ULTIMA Gold uLLT
0.111
0.887
0.766
3.788
921
ULTIMA Gold LLT with sample
0.260
1.359
1.100
5.789
814
ULTIMA Gold uLLT with sample
0.226
1.214
0.988
3.124
818
cpm A
cpm B
cpm C
tSIE
% Lum
UG-LLT ref
3,87
5,61
7,2
729
1
UG-uLLT
3,56
4,29
5,82
759
0
Table 2. Background levels in Tri-Carb for UG-LLT and UG-uLLT
LSC cocktail
High efficiency
High sample uptake
A LSC cocktail with a high counting efficiency allows more
accurate results and shorter counting cycles. The efficiency
depends on the amount of sample added (dilution), but
should be as high as possible at maximum sample loads.
The efficiency also depends on the count mode selected:
normal count mode (0 – 18.6 keV — Figure 2) or Low Level
count mode (0 – 18.6 keV — Figure 3). Overall, ULTIMA Gold
uLLT has a similar counting efficiency as ULTIMA Gold LLT
as can be seen from the figures below.
Low level applications are preferably done with larger amounts
of sample to reduce the counting times. As can be seen from
the data below, higher sample loads are offset by a reduction
in efficiency. For low level environmental monitoring applications, sample quantities of 8 - 10 ml added to 10 ml LSC
cocktail are considered optimal. In Figures 4 and 5 below
you will find an overview of sample capacities for different
water samples. The sample uptake for ULTIMA Gold LLT
is comparable to ULTIMA Gold uLLT.
Counting efficiency low level (0 - 18.6 keV)
60
50,0
50
40,0
UG -L L T
30,0
UG -u L L T
20,0
10,0
% efficiency
% efficiency
Counting efficiency normal level (0 - 18.6 keV)
60,0
40
UG -L L T
30
UG -u L L T
20
10
0,0
0
0 : 10
8 : 12
8 : 10
10 : 10
12 : 10
0 : 10
8 : 12
Ratio water / cocktail (ml)
8 : 10
10 : 10
12 : 10
Ratio water / cocktail (ml)
Figure 2. Counting efficiency for tritium in normal count mode in Tri-Carb
Figure 3. Counting efficiency for tritium in low level count mode in Tri-Carb
Sample load ULTIMA Gold uLLT
Sample load ULTIMA Gold LLT
Sea Water
Sea Water
20°C
20°C
Tap water
Tap water
18°C
18°C
16°C
16°C
14°C
Distilled water
14°C
Distilled water
12°C
12°C
Deionized water
Deionized water
0
2
4
6
8
10
0
12
Figure 4. Sample load capacities for UG-LLT
2
4
6
8
10
12
Figure 5. Sample load capacities for UG-uLLT
Ordering information
ULTIMA Gold uLLT is available in 3 formats, dispensed in glass amber bottles:
6013683
ULTIMA Gold uLLT
500mL Sample
6013681
ULTIMA Gold uLLT
1 Liter
6013687
ULTIMA Gold uLLT
4 x 2.5 Liter
PerkinElmer, Inc.
940 Winter Street
Waltham, MA 02451 USA
Phone: (800) 762-4000 or
(+1) 203-925-4602
www.perkinelmer.com
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