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 For a complete listing of our global offices, visit www.perkinelmer.com/lasoffices ©2008 PerkinElmer, Inc. All rights reserved. The PerkinElmer logo and design are registered trademarks of PerkinElmer, Inc. ULTIMA Gold is a trademark and QUANTULUS and Tri-Carb are registered trademarks of PerkinElmer, Inc. or its subsidiaries, in the United States and other countries. All other trademarks not owned by PerkinElmer, Inc. or its subsidiaries that are depicted herein are the property of their respective owners. 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