An annular helium plasma at atmospheric pressure was generated by the 2.45 GHz microwave power (∼1 kW) with Okamoto cavity, and the physical and analytical characteristics were summarized. The electron density and iron excitation temperature of high energy part for the He plasma were on the order of 10¹⁴/cm³ and 6,500 K, respectively. An aqueous solution with non-metal was injected into the plasma by the ultrasonic system with desolvation and condensation. Intense atomic and/or ionic emissions were detected and the detection limit of 100 ppb for F I (685.6 nm), 100 ppb for Cl II (479.5 nm), 150 ppb for Br II (487.5 nm), 1ppb for C I (247.9 nm), 2 ppb for P I (213.6 nm) and 0.02 ppb for Mg II (279.6 nm) and Ca II (393.4 nm) were obtained.