The experiments showed that a beam is stable over a
distance of at least 15 cm if its speed is higher than
about 12 m/s. Using a nozzle of 50 :m inner diameter,
a 1.42 mL/min flow rate is necessary to reach this
speed. The typical shape of a smooth jet nozzle is a
cylinder with a ratio length/diameter > 3. The pressure drop of such a nozzle is less than 0.5 bar which
allows the use of low-pressure pumps, for instance a peristaltic pump, for the beam generation.
The requirements for the material of the tube furnace include good stability and chemical resistance
against the corrosive conditions of an acetylene/air flame and water and acid vapors at temperatures higher
than 1000 /C.
Suitable tube materials are pure nickel, super alloys or non-porous Al2O3 ceramic. To increase the
temperature inside the furnace and to achieve a more reducing atmosphere, a tube with 4 or more
additional holes located on the bottom side is used.
Currently, 25 elements have been determined
using BIFF-AAS, of which 17 elements (Ag, As,
Au, Bi, Cd, Cu, Hg, In, K, Pb, Pd, Rb, Sb, Se,
Te, Tl, Zn) exhibit an improved power of
detection from 6 fold to 202 fold compared to
conventional FAAS [1]. The standard deviation
amounts to 1.7 - 4.0 % (N = 12; 50 :L
samples). Fig. 3 shows the signals of Cd sample
in the low :g/L range measured with BIFFAAS.