For a biology experiment titled Spectrophotometry 1 Describe

For a biology experiment titled \"Spectrophotometry\"

1.) Describe the steps to clean cuvettes when you finish lab procedures

2) What are the two reasons for measuring the absorbance of a sample at its max?

3) What is the purpose of using a blank specimen in calibrating the spectrophotometer (to autozero the machine) ?

Solution

1) Wash with water and ethanol twice let it dry then keep it in UV for 20 min

2)

A) When taking the absorbance at max, a small change in absorbance will only cause a small error. However, if the measurement is taken at a different value, a small shift can cause a large error.

B) Absorbance at max will give most accurate result because small change in the concentration leads a large change in max.

3 .To make baseline absorbance zero it will give more accurate result. you are not actually measuring the absolute absorption of the sample, but the sum of all light loss between the light source and the detector. Some of that light is simply not aimed directly at the detector, some of it is scattered by the cuvette, some is absorbed by the cuvette, so blank reading insure the absolute reading of your sample.