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Table of Contents
An Introduction to Beer-Lambert Law
Analytical chemistry is based on the Beer-Lambert Law, sometimes referred to as Beer's Law. It creates a linear connection at a certain wavelength between a solute's concentration in a solution and light's absorption. It is named after two scientists who helped shape it in the 19th century: August Beer and Johann Lambert.
Formula
- The equation: represents the Beer-Lambert Law.
- A = ε * c * l
- A: Light absorption (unitless)
- E (epsilon) Molar absorptivity (L mol 1 cm 1), often known as the molar absorptivity coefficient
- c: Solute concentration (mol/L)
- l: The sample's path length (in cm)
Key points
Absorption (A)
- Represented by the unit: A
- It is the measurement of the quantity of light that a sample absorbs.
- Spectrophotometer is the instrument used to measures the intensity of light. It measures the intensity of light before & after passing through a material or substance.
- The relationship between absorbance and path length and the solute concentration is linear.
Molar absorptivity:
- A substance's innate ability to absorb light at a certain wavelength is known as its molar absorptivity ().
- Greater absorption is indicated by higher readings.
- is particular to the substance and the measured wavelength of light.
Concentration
- The amount of solute present in a specific volume of solution is known as concentration, or c.
- unit: moles per liter (mol/L).
- With a constant path length and, absorbance increases along with concentration.
Path length
- The length of the path that light takes through a sample is denoted by the letter l.
- It is a key component of the Beer-Lambert Law and is often measured in centimeters (cm).
- Given constants and c, a longer path length causes a larger absorbance.
Applications of beer Lambert law
Quantitative Analysis
- The Beer-Lambert Law is usually used for quantitative analysis, in analytical chemistry.
- It calculates a substance's concentration in a solution by measuring its absorbance by using this law.
Spectrophotometry
- Spectrophotometers (instrument used to measure light intensity) are required in analytical chemistry laboratories.
- They determines the absorbance of light at a specific wavelengths and the concentration of analytes using this law.
Biochemistry & Pharmaceuticals
The beer Lambert law is widely used in pharmaceutical as well as biochemical studies in order to determine the concentration of medicines, proteins and its constituents and other biomolecules, it helps with research and quality control.
Limitations or Drawbacks
Linearity
According to the Beer-Lambert Law, absorbance and concentration have a linear relationship. Due to things like chemical interactions & instrumental constraints, deviations from linearity may happen at very high or very low concentrations. Since the rule depends on wavelength, various compounds may have different values at various wavelengths. For precise measurements, the right wavelength must be carefully chosen.
Conclusion
With its simple mathematical relationship, the Beer-Lambert Law is a crucial tool in chemistry (analytical chemistry). It is involved in precise measurements of the substance concentration in solutions. This law is important to contemporary analytical procedures, whether in pharmaceuticals, or environmental monitoring as well as biochemistry, as it advances both research and industry.
Hand Written Notes
Find hand written notes to the beer-lambert law below.