Unmatched Optical Performance

04-Optics

Optics

The optical design is the heart of any spectrometer, and at GBC we have a long history of quality optical systems.
The large, self-calibrating 333 mm (focal length) monochromator has been specifically designed to provide the high light throughput and stability needed for atomic absorption.
Spectral bandwidth is continuously adjustable between 0.1 and 2 nm (in 0.1 nm inctrements) and, for furnace work, reduced slit height is available with all slit widths. A wide-range photomultiplier tube covers the full wavelength range (175–900 nm).

The SavantAA range provides unmatched optical performance by:

  • The use of the most ecient all-reflective optics (not inferior lenses).
  • The use of minimal optical components (to ensure maximum light throughput).
  • The monochromator is designed for maximum effciency for all wavelengths.
  • The unique Asymmetric Modulation to improve signal to noise ratio.

Conventional double beam instruments measure the light in both the sample and reference beams for equal duration, Asymmetric Modulation allows the light in the sample compartment to be measured for twice the duration of the sample beam measurement. As the sample compartment is the area in which all the noise is generated in any AAS, Asymmetric Modulation improves the signal-to-noise ratio by as much as 40%. This results in unmatched performance in both sensitivity and detection limit.

Hyper-Pulse background correction

The Hyper-Pulse background corrector, available on the SavantAA and SavantAA Σ – one of the fastest systems available, has been further improved by pulse interpolation. This allows for more accurate interpolation of “Transient Signals” such as GF signals. High intensity deuterium arc lamp provides 175–425 nm correction range. With all background correction systems, there is a small time delay between the measurement of background and total absorbance.

When the Background is changing very rapidly, as is often the case with graphite furnace work, this delay can lead to an error in the background corrected reading. Systems with slower sampling rates and longer delay times show greater errors.

Most background correctors measure the background absorbance 50 or 60 times per second and the delay between the measurement of background and total absorbance can be as much as 10 milliseconds.

The GBC Hyper-Pulse system takes 200 (50 Hz) or 240 (60 Hz) sample measurements per second and the delay between the measurement of background and total absorbance is about 1 millisecond. This produces a dramatic reduction in background correction errors. Accuracy is further improved by interpolating between background measurements to calculate the background when the atomic signal is measured.
This system also allows correction for higher background levels than most systems – up to 2.5 total absorbance.