[en] The liquid scintillation Efficiency Tracing (ET) technique is a practical method of quantifying radionuclides being analyzed in a liquid scintillation analyzer. This technique has several advantages over conventional liquid scintillation methods: no quench curve (quenched standard set) is required for each nuclide being analyzed; only a single unquenched ¹⁴C sample (same as that used to normalize the liquid scintillation analyzer) is required to calculate radionuclide activity (DPM) or concentration; the technique can be used effectively for almost all pure beta and beta-gamma emitters (minimum energy = 70 keV). A Tri-Carb 2100TR Liquid Scintillation Analyzer from Packard was used to perform a series of experimental works to assess performances of ET method. In this paper are presented the results obtained for activity determination of ¹⁴C samples with various quench and activity levels. The experimental tests were made using both the ET method implemented on the analyzer by the producer and our ET method, using the reference spectrum of the unquenched ¹⁴C standard, used to normalize the liquid scintillation analyzer. The results indicate that the measured values using implicit ET method are in good agreement (uncertainty ≤ 3,5 %) with the reference values only for samples with a quenching level not very high (quenching indicating parameter tSIE > 200 - 300). Otherwise, using our ET method, good results (percent recovery more than 96.5%) were obtained for any quenching level (tSIE > 100) even at a count rate level one order of magnitude lower than it is recommended for this method. (author)