| As rare earth is more and more applied in agriculture and industry, its toxicity to human and metabolization in food chain have drew great attention in recent years. Determination of rare earth ions is base of these studies. Although fluoremetry analysis is one of the most important methods, fluorometry determination for single rare earth ions is still difficult, and only a few kinds of rare earth ions, such as Tb3+ and Eu3+ could be determined. However, as more and more rare earth complexes which could give strong near-infrared luminescence was found, fluorometry determination of Nd3+, Yb3+ and Er3+ ions is possible. In the present work, fluorometry determination of Yb3+ was studied using 1 -(2-pyridylazo)-2-naphthol (PAN), pyridine-(2-azo-4)resorcinol (PAR), chrome blue-black R(CBBR) and eosin.Rare earth complexes ( rare earth = Nd3+, Yb3+ and Er3+) were PAN,PAR,CBBR and eosin was first synthesized. The condition for coordination reaction, facts influence near infrared fluorescence intensity were studied. The near infrared fluorescence properties were discussed based on the energy transfer mechanism. In the present condition, Yb3+ ions could be determined using PAN with linear range of 1.0 X 10-6 -- 8.0 X 10'6mol/L, and using chrome blue-black R with linear range of 2.0 X 10-6 -1.6X 10-5mol/L . It was also found that addition of a second ligand such o-phenanthroline hydrate could greatly enhance near infrared of some complexes. And a more sensitive method was developed using eosin and o-phenanthroline hydrate with linear range of 8.0 X 10"7 -2.6 X 10"5mol/L these results indicated that near infrared fluorometry should be a promising method for determination of single rare earth ions.
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