报道了Pb和Cd同时氢化物发生的K3Fe(CN)6-(NH4)2Ce(NO3)6-NaBH4-HCl新体系,并探讨了相关反应机理。(NH4)2Ce(NO3)6作为氧化剂将Pb(Ⅱ)氧化为Pb(Ⅳ),Fe(CN)^3-6与Pb(Ⅳ)络合促进了Pb的氢化物发生。同时,体系中的(NH4)2Ce(NO3)6作为Cd氢化物发生过程中的增敏剂使荧光信号显著增强。在该体系中,Pb和Cd的氢化物发生不产生相互干扰。本实验据此建立了顺序注射-氢化物发生-双道原子荧光同时测定Pb和Cd的方法。所采用的实验条件包括NaBH4、HCl、K3Fe(CN)6和(NH4)2Ce(NO3)6的浓度分别为2%、3%、0.6%和0.3%。以125μL/s进样500μL,得到的线性范围分别为0.4-15μg/L(Pb)和0.5-20μg/L(Cd);对应的检出限分别为0.09μg/L(Pb)和0.17μg/L(Cd);方法的精密度为0.5%(6.0μg/L Pb,n=9)和1.0%(6.0μg/L Cd,n=9)。将本法应用于国家标准样品GBW08608中Pb和Cd的检测。检测值与标准值相符;对河水及海水中Pb和Cd进行了同时测定,加标回收率合格。
A novel hydride generation system was developed for the simultaneous hydride generation of lead and cadmium, i.e., the system of K3 Fe (CN) 6- ( NH4 ) 2 Ce ( NO3 ) 6-NaBH4-HCl, which no interfering effects from the hydride generation of the two species were identified. The mechanisms of the hydride generation process include the oxidation of Pb (Ⅱ) by ( NH4 ) 2 Ce ( NO3 ) 6, meanwhile, the K3 Fe (CN) 6 was used as a coordinating reagent to form a complex with Pb( Ⅳ ) which facilitates its ensuing hydride generation. Cadmium hydride generation follows the conventional process with (NH4 )2 Ce( NO3 )6 serves as a sensitizer. A sequen- tial injection-hydride generation-atomic fluorescence spectrometric procedure was developed for the simultaneous determination of lead and cadmium. When employing the following experimental parameters, i. e. , 2% NaBH4o3% HCl -0. 6% K3Fe(CN) 6-0. 3% (NH4) 2 Ce( NO3 )6, a 500-μL sampling volume at a flow rate of 125 μL/s, the obtained linear ranges were 0. 4 - 15 μg/L (Pb) and 0. 5 -20 μg/L (Cd) respectively, along with limits of detection of 0. 09 μg/L (Pb) and 0. 17 μg/L (Cd). The RSDs of the procedure were derived as 0.5% (6.0 μg/L Pb, n =9) and 1.0 % (6.0 μg/L Cd, n =9). The present procedure was applied for the determination of lead and cadmium in a certified reference material of water sample, GBW08608, a coastal sea water and a riverine water sample, with satisfactory spiking recoveries.