Determination of Cd and Pb at microg/L levels by HHPN-beam injection flame furnace-AAS

Flame-heated tubes are widespread in flame-AAS, mainly for the determination of hydride-forming elements. Instead of the introduction of gaseous compounds liquids can also be introduced continuously in such an absorption cell. With the aid of an HPLC pump the liquid is forced through a very fine nozzle, generating an aerosol beam less than 0.5 mm in diameter. This beam travels a distance of 10cm as a "free-flying aerosol jet" into the sample introduction hole of a metal tube furnace placed in the flame. Both introduction of the entire sample and the long residence time lead to a considerable improvement in power of detection. The detection limit for 100 microL samples amounts to 7 microg/L (Pb) and to 0.2 microg/L (Cd), which means an increase in power of detection of between one and two orders of magnitude compared to conventional flame-AAS. The relative standard deviation (100 microL sample volume, N = 10) was found to be 1.3% (signal area) for 600 microg/L Pb and to be 1.5% (signal-area) for 15 microg/L Cd. RSD values from measurements in peak-height amounted to 2.2% (Pb) and to 1.7% (Cd).