|
A matrix modification was studied for the determination of trace germanium in mineral waters by electrothermal atomic absorption spectrophotometry (ET-AAS). For this, the type and quantity of modifier as well as the use of auxiliary modifier were investigated to realize the efficient modification. Germanium suffers from low sensitivity and poor reproducibility in ET-AAS determination because of the premature loss of germanium via volatile germanium monoxide formation when heated in the presence of carbon. Therefore, the addition of a matrix modifier is necessary to stablize the germanium, thermally and chemically. By the addition of palladium (10 μg/mL) as a single modifier to the sample containing 500 ng/mL germanium, the charring temperature could be raised from 800 to 1,000℃ and its absorbance was also increased, but the atomization temperature was not raised. In this case, the absorbance of germanium was not changed in the range of 10∼70 μg/mL of palladium added. On the other hand, it was considered that the use of a mixed modifier could modifiy the matrix more effectively than with a single modifier. The best results were obtained by using 1% ammonium hydroxide as an auxiliary modifier together with 10 μg/mL palladium. The charring temperature could be raised from 800 to 1,100℃ without any change of the atomization temperature. With above optimum conditions, the trace amount of germanium in several mineral waters were determined by a calibration curve method, and good recoveries of more than 95% were also obtained in the samples in which a given amount of germanium was spiked. The detection limit of this method was about 6.9 ng/mL.
|