[en] Highlights: • A new simplest method for radium quartet measurement was evaluated. • ²²⁵Ra as isotopic tracer was used. • A depth study of ²²⁵Ra-²²⁵Ac separation was carried out. - Abstract: A new method for the determination of radium quartet (^{223,224,226,228}Ra) in environmental samples by alpha-particle spectrometry with PIPS detectors is described. This uses ²²⁵Ra as yield tracer, in equilibrium at the beginning with ²²⁹Th. Thorium is removed from the sample by using AG1X8 anion-resin, and then radium isotopes are isolated and purified with a cation-exchange column Biorad AG50X8, verifying that Ac has been fully removed from the sample to ensure the good evaluation of the Ra yield (average decontamination factor > 92%). Finally, the counting source of radium is obtained by micro-precipitation with BaSO₄. This method produces high spectral resolution (70%). In this new method, NH₄Ac in 0.1 M HNO₃ is used to remove the ²²⁵Ac contained in the sample in order to avoid its future spectral interference in the yield calculation. The method has been validated by using certified reference samples with known concentrations of radium isotopes.