The integral counting method of liquid scintillation counting has been modified by extrapolating the integral pulse-height spectrum to the zero detection threshold of the liquid-scintillation system rather than to the zero pulse-height, and applied to the determination of 222Rn samples. The results have been compared with those obtained by the conventional integral counting method and the efficiency tracing method. The modified integral counting method gives more accurate results than the conventional integral counting method and the efficiency tracing method. The possibilities and limitation of the efficiency tracing method has been discussed.
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