It has baen found that sulfosalicylic acid(SSA)in the presence of Co(Ⅱ)in alkaline hydrogen peroxide solution ischemiluminescent. The emit-ted CL spectrum is detected by an Optical Multichannel Analyzer (B & MSpectronic WP4)with a cooled camera. The concentration range of the linearity response is 6×10~(-10) to ×10~-7g/ml, and detection limit is less than 0.001ppb. Foreign ions such as Fe(Ⅲ), Ni(Ⅱ), Mn(Ⅱ)and Sn(Ⅳ)interfere when they present twice as much as Co(Ⅱ), and some other ions, even 10 to 100 times p...