A versatile and robust method for the determination of DNA and PCR products (<500 bp) is presented, based on a mix of an Eu^III chelate and acridine orange (AO). The nucleic acid selective stains acridine orange (AO) and ethidium bromide (EB) quench the luminescence of the bimetallic [Eu₂(L^C2)₃] and of other monometallic chelates such as the macrocyclic complex [Eu(L^kel)], even at very low molar ratios. Stern–Volmer plots of the metal-centered emission intensities (F₀/F) and Eu(⁵D₀) lifetimes (τ₀/τ) show the AO quenching being purely dynamic with K_D = 6.7 × 10⁵ M⁻¹ for [Eu₂(L^C2)₃] and 1.6 × 10⁶ M⁻¹ for [Eu(L^kel)], and bimolecular rate constants k_q = 2.7 × 10⁸ M⁻¹ s⁻¹ and 3.4 × 10⁹ M⁻¹ s⁻¹, respectively. On the other hand, EB quenching is due to both dynamic and static mechanisms. In the presence of various types of DNA > 0.1 ng μL⁻¹ (dsDNA, ssDNA or circular DNA), the quenched luminescence is reinstated, AO and EB intercalating into DNA, which removes the interaction with the Eu^III complexes. The best results are obtained with [Eu₂(L^C2)₃]/AO with detections limits in the range 0.18–0.66 ng μL⁻¹; detection limits for the [Eu(L^kel)]/AO system are slightly larger; simpler monometallic Eu^III complexes with dipicolinate derivatives do not follow suit in that they decompose in the presence of DNA. The Eu^III/AO method is shown to be pH insensitive in the range 3–10; furthermore it is essentially insensitive to 1000-fold excesses of potential interfering substances, e.g. BSA, glucose, chelating agents and anions, alkaline earth and transition metal cations, variations in luminescence intensity being < 5%, (10 analytes) or 5–10% (4 analytes); only Co^II and Cu^II interfere substantially.