Multiple Choice
Which of the following best describes the relationship between the concentration of allura red dye solutions and their absorbance, according to Beer-Lambert Law?
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17. Fundamentals of Spectrophotometry
Measuring Absorbance
Multiple Choice
In UV-Vis spectrophotometry, what is the primary purpose of constructing a calibration curve when measuring absorbance?
A
To verify that the cuvette path length is exactly for all measurements
B
To remove instrumental noise by subtracting the blank absorbance from every sample automatically
C
To relate measured absorbance to analyte concentration so an unknown concentration can be determined from its absorbance
D
To determine the wavelength of maximum absorbance () for the analyte
Verified step by step guidance1
Understand that in UV-Vis spectrophotometry, absorbance (A) is related to the concentration (c) of the analyte by the Beer-Lambert Law, which is expressed as \(A = \varepsilon \times b \times c\), where \(\varepsilon\) is the molar absorptivity and \(b\) is the path length of the cuvette.
Recognize that the calibration curve is constructed by measuring the absorbance of a series of standard solutions with known concentrations under the same conditions.
Plot the absorbance values on the y-axis against the known concentrations on the x-axis to create a calibration curve, which should ideally be a straight line if Beer-Lambert Law is obeyed.
Use the linear equation derived from the calibration curve (usually in the form \(A = m \times c + b\), where \(m\) is the slope and \(b\) is the intercept) to relate absorbance to concentration.
Apply this calibration curve to determine the concentration of an unknown sample by measuring its absorbance and then using the curve equation to find the corresponding concentration.
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