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P4CIFICO

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posted by P4CIFICO on 10/2/2008 8:39:39 PM | status: Live

Spectrophotometry Q please help

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Question Details:

Why must the spectrophotometer be rezeroed with the blank every time the wavelength is changed?

Tags: Biology

Answers:

licy

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posted by licy on 10/15/2008 2:02:02 AM | status: Live

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Response Details:

In a reaction mixture , it is important to first “zero out’’ the spectrophotometer so that only the absorbance of the substance of interest is measured . This is done with a blank, a cuvette which contains all the carrier solvents except the substance of interest. A separate blank is needed for every unique reaction mixture.

When taking several measurements at the same wavelength over a short time period, we do not reblank for each. Over longer times, the unit may drift and recalibrations to the blank will be necessary. How ever, you change the wave length you must re- zero the instrument. If you are taking the readings over an extended period or sharing the instrument, re-zero for each measurement.

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