Varian SpectrAA Zeeman
The Zeeman effect
The Zeeman effect is the splitting and polarization of atomic spectral lines in
the presence of a magnetic field. Molecular species and particulates that can cause background absorption remain relatively unaffected by the magnetic field. The Zeeman technique uses a magnetic field to achieve accurate background correction. With the magnet off, the total absorbance is measured. With the magnetic field applied, splitting of the spectral profile occurs, and only the backgroun is measured. The atomic absorbance signal is determined by subtracting
the background absorbance (magnet on) from the total absorbance (magnet off).
The Varian solution
Zeeman background correction is a powerful tool, but requires correct design to deliver accurate answers. The SpectrAA Zeeman features the sensitive transverse AC modulated Zeeman configuration, which has the field applied across the atomizer. This avoids the sensitivity losses observed with a DC (permanent) magnet and maximizes light throughput compared with longitudinal designs where end caps restrict the light passing through the pole pieces
of the magnet. Varian’s patented magnetic- field waveform provides a delay time of
less than 5 ms between measurements and collects 100/120 data points (50/60 Hz) every second.
For accurate correction the instrument must determine the true background at the time the total signal was measured. Some instruments use simple linear interpolation of the background, which can result in erroneous calculations of the background signal if this signal is changing rapidly (a common occurrence with furnace analyses). SpectrAA Zeeman uses three- point polynomial interpolation to accurately track the actual shape of the peak and correctly calculate the background signal at the time the total signal was measured.
Varian GTA 110
Constant Temperature Zone design
Varian’s furnace research has demonstrated that the best graphite furnace performance is achieved using a Constant Temperature Zone (CTZ) graphite furnace. The CTZ is created by carefully matching the design
of the GTA-110 power supply to low thermal mass, end-heated graphite tubes. This ensures extremely fast atomization for the best signal-to-noise characteristics with difficult sample matrices.
The GTA-110 also features the most advanced furnace sampling systems. Analytical cycle times are reduced and performance is improved using hot injection and synchronized sampling.
Varian’s longitudinally heated GTA-110 CTZ graphite furnace with transverse Zeeman background correction provides outstanding performance at ppb levels with the flexibility to handle difficult samples speedily and effectively. This comes from the proven efficient furnace design,
the patented dynamic feedback temperature control and flexibility in gas and temperature programming.
Source: Varian SpectrAA 220/880 Zeeman