Question

The burner head in the atomic absorption experiment was perfectly aligned with the line of view of the detector (compare to tilting the burner head during the atomic emission experiment). If the burner head was left tilted, how would (1) the sensitivity of your calibration method and (2) the random error in the calculated concentrations of the unknown be affected? (i.e. think what would be affected in your calibration curve)?  

Answer 1

The burner head position (both vertical and horizontal positions ) must be so aligned so that cathode lamp light directly passes through the burner slit (no blocking permitted to avail maximum signal by the detector)

Gaseous atoms absorbs the incident radiation(of intensity,Io) passing through the slit,thus the final intensity of beam (I) being detected by the detector

According to Beer's law,

Absorbance=A=log (Io/I)=abc ,c=concentration of absorbing species,b=path length of light,a=absorptivity of light

1) If the burner head is tilted then,the detector does not detect the passing radiation properly.

Thus ,inal intensity of beam (I) being detected by the detector is less comparatively,thus % transmittance will be low, giving high absorbance value than actual,thereby giving high concentration value of the absorbing species.The callibration curve betwee A vs C will give erroneously high concentration values for unknown sample.

2) The callibration curve betwee A vs C will give erroneously high concentration values for unknown sample.