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Comparison study of quench levels for estimation of low level
H-3 activity by liquid scintillation counting using TDCR based
Hidex 300SL and LKB Wallac Quantulus1220
1Anil
Gupta, 2Sonali Bhade, 2P. J. Reddy, 1P. K. Kale, 1K. Narayanan Kutty,
2D.A.R. Babu, 1R. G. Purohit and 1Dr. P. K. Sarkar
1Health
2Radiation
Physics Division,
Safety Systems Division,
Bhabha Atomic Research Centre, Mumbai – 400 085
INTRODUCTION
 Widely used Liquid Scintillation Counter (LSC) LKB Wallac Quantulus 1220 and the newly introduced TDCR based Hidex 300SL were calibrated for H-3
estimation.
 Samples spiked with H-3 with varying levels of quench were quantified using Hidex 300SL LSC and the results obtained were compared with LKB Wallac
Quantulus 1220.
 The difference between two LSC systems is mainly the use of two different quench indicating parameters (QIP) namely Spectral Quench Parameter of External
Standard (SQP (E)) in Quantulus 1220 and Triple to Dual Coincidence Ratio (TDCR) in Hidex 300SL.
 These parameters are used to correct quench associated with samples. The present study was carried out to determine the correlation of these two QIPs with
the counting efficiencies to arrive at the precise activities.
MATERIALS AND METHODS
 LKB Wallac Quantulus 1220 and Hidex 300SL liquid scintillation analyzers.

3H
capsule (Emax-18.6keV) Standard (Packard).
 Quantified H-3 samples of different activity range varying from 1.4 Bq/ml to
0.27 Bq/ml using both the instruments.
RESULTS
 Scintillation cocktail: Quicksafe-400 (Zinsser Analytic).
 Hidex 300SL, LSC gives consistent results for all quench levels whereas in
 Nitromethane (Merck, Germany) as chemical quencher.
 Scintillator : sample ratio (12:8).
case of Quantulus 1220, as the quench increases, there is a sharp rise in
 H-3 quenched standards ~82.5 Bq (or ~10.3 Bq/ml) were prepared.
the percentage deviation while quantifying activity as depicted in Table 1.
 Counting time for both the instruments 500 min.
 In TDCR, triple and double coincidences are measured and the ratio of
these coincidences is calculated.
Table 1: Calculated 3H activity using Quantulus and Hidex 300SL LSCs along with
% deviation w.r.t. reference activity.
Reference SQP(E) TDCR Calculated 3H activity % deviation w.r.t. ref.
3H activity
Value
value
(Bq/ml)
activity
(Bq/ml)
Quantulus
Hidex
Quantulus
Hidex
LSC
300SL LSC
300SL
RST : Triple Coincidence Counts;
RS : Double Coincidence Counts;
RT : Double Coincidence Counts;
ST : Double Coincidence Counts;
TDCR: Triple Double Coincidence Ratio
Ct : triple coincidence counts
Cd : double coincidence counts
Call: all coincidence counts
 Calibration curve of Quench Indicating Parameter (TDCR value for Hidex
and SQP(E) for Quantulus) vs %counting efficiency obtained.
1.41
835.1
0.274
1.46
1.34
-3.94
4.96
0.69
838.3
0.271
0.73
0.70
-5.0
1.4
0.40
836.9
0.265
0.43
0.41
-5.15
-2.5
0.27
837.8
0.263
0.29
0.28
-6.86
-3.7
 For scintillator : sample, 10:1 composition (low quench levels or low water
load) the TDCR value is proportional to percentage efficiency.
 The proportionality factor is ~1 whereas for mixing ratio of scintillator :
25
25
sample, 12:8 composition (higher quench levels or high water load), the
proportionality factor does not remain 1.
20
15
15
%EFF.
%EFF.
20
CONCLUSION
10
In Hidex 300SL LSC TDCR method, quench affects the quantification of H-3
10
5
activity to a lesser extent compared to the Quantulus 1220 liquid scintillation
5
0.08
0.12
0.16
0.20
0.24
TDCR
Fig: 1 TDCR vs % Efficiency
0.28
0
600
650
700
750
800
850
SQP(E)
Fig: 2 SQP(E) vs % Efficiency
counting. TDCR is an absolute standardization method. For low water load
TDCR value is proportional to percentage efficiency (proportionality factor
is ~1). For higher water load TDCR is linearly proportional to percentage
efficiency with some intercept.