Difficulty Beyond 5.0 ABS

We're trying to get a reading from a Cary 5000 above a 5.0 absorption between 200-400nm. Specifically, we want to measure between 7 and 8 ABS, but we're getting erratic readings starting around 5.8-6.2 ABS, and cannot get any workable data once we are outside of visible ranges.

Any help, manuals or guides you can point me to would be greatly appreciated!

  • Hello

    Are you using a Rear beam attenuator? This is recommended when measuring at high absorbances. The reason for this is because the Cary compares how much light gets through the sample beam, and then through the reference beam and then calculates the absorbance or transmittance based on the difference in light throughput between the two (this happens very quickly). At high abs, very little light gets through the sample path (5abs is only .00001% T), and a very high amount of light through the reference path (typically 100%T). It’s hard on the detector to see so little light, followed by lots of light, and make a stable reading. 

    A rear beam attenuator is basically a screen in the reference path that blocks some light in order for the instrument to give better readings at high absorbance values.

    Please contact your local Agilent Molecular spectroscopy representative about Agilent’s Rear Beam Attenuator options. Hope that helps and have a great day


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