The mercury adsorbed and deposited on phosphor plays an important role in light reduction during fluorescent lamp operation. However the coating treatment for phosphor or coating a film on lamp tube may reduce the adsorption-deposition of mercury and then degradation of light efficiency. A method for the determination of mercury amount on phosphor by cold vapour atomic absorption spectrometry is proposed. The method is based on the absorption of mercury atoms at 254nm resonance line at room temperature. Such absorption is directly proportional to concentration of mercury vapour. In the experiments

mercury was reduced by adding the reducer to a series of standard solutions of mercury and was then blew into the light path of the mercury surveymeter. The calibration curve was obtained. At the same time

monochromatic fluorescent lamps were prepared by using blue emitting BAM phosphor and coated BAM phosphor with nano-scale Al

2

O

3

film respectively. After different lighting times

the mercury contents of the phosphors were measured. The regression equation of the calibration curve was found to be Y= 0.4455

X

+0.2000. A linear relationship between the experimental signal and mercury content was attained when the mercury concentration was below 2.4×10

-2

μg/mL. The recovery was 92.3~99.8% for samples analyzed by standard additions method. Therefore the method was found to meet the demand for determination of mercury content on phosphor.It is proved that the mercury content adsorbed on blue emitted phosphor samples increases with lamp operation time and is accompanied by a decrease of the brightness. Therefore

the light reduction can be mainly attributed to the adsorption and deposition of mercury. Moreover

compared to the coated BAM phosphor by nano-scale Al

2

O

3

film

the mercury content of uncoated phosphor was evidently larger. Thus

the coating treatment of the phosphor can protect the powder and reduce the adsorption-deposition of mercury. As a result

the degradation of light efficiency of the coated BAM phosphor is inhibited in the course of lighting.