Question

Why do we only record absorbance at a wavelength that gives the greatest absorbance value for Allura Red (wavelength max)?

a) To minimize the amount of light absorbed
b) To simplify the calibration curve
c) To enhance the sensitivity of the measurement
d) To speed up the spectrophotometer analysis

Answer 1

We record absorbance at the wavelength max, or Amax, to enhance the sensitivity of the measurement, which is crucial for accurately quantifying the concentration of a substance like Allura Red using the Beer-Lambert Law.

Step-by-step explanation:

The reason we record absorbance at the wavelength that gives the highest absorbance value for Allura Red, also known as the wavelength max or Amax, is to enhance the sensitivity of the measurement (option c). The maximum absorbance corresponds to the wavelength where the substance, in this case, Allura Red, most strongly absorbs light. This is crucial for quantifying the concentration of the substance accurately using the Beer-Lambert Law, which describes the linear relationship between absorbance and concentration within certain limits. At Amax, the value of absorbance provides the most sensitive and accurate representation of the sample’s concentration due to its high absorbance at this specific wavelength. Furthermore, since absorbance and concentration have a direct relationship, as described by the Beer-Lambert Law, measuring at Amax offers a more straightforward path to calculating the concentration using the molar absorptivity or extinction coefficient, which is unique to each compound at a given wavelength.