UV-Vis Spectrophotometry
Also known as: UV-Vis spectroscopy, absorption spectroscopy, colorimetry
UV-Vis spectrophotometry is an optical analytical technique that measures the absorption of ultraviolet and visible light (wavelengths 190–900 nm) by substances in solution. Founded on the Beer-Lambert law (developed by August Beer and Pierre Bouguer), it is one of the oldest and most widely used quantitative analytical methods. UV-Vis spectrophotometry is economical, rapid, and applicable to a vast range of organic and inorganic compounds, making it indispensable in pharmaceutical, clinical, environmental, and research laboratories.
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When to use it
UV-Vis spectrophotometry is ideal for analyzing organic compounds (pharmaceuticals, vitamins, dyes, proteins) and transition metal complexes that absorb in the UV or visible range. Use this method for rapid, nondestructive analysis of solutions when high precision is not critical (relative standard deviation typically 1–5%), when cost-effective instrumentation is preferred, or when sample volume is limited. The method excels in pharmaceutical quality control, clinical chemistry (protein assays), and environmental monitoring of colored contaminants.
Strengths & limitations
- Rapid analysis with minimal sample preparation
- Cost-effective instrumentation with widespread availability
- Non-destructive detection allows sample recovery or further analysis
- High sensitivity for compounds with strong chromophoric groups
- Excellent for colorimetric assays using color-developing reagents
- Suitable for high-throughput analysis with multiwell plate readers
- Only applicable to compounds that absorb UV or visible light
- Spectral overlaps and interference from other absorbing species limit selectivity
- Requires sample to be in solution (transparent cuvette needed)
- Background absorption from the solvent and cuvette material limits detection sensitivity
- Non-selective (does not provide structural information like mass spectrometry or chromatography)
Frequently asked
What is the difference between absorption and transmission?
Transmission (T) is the fraction of light that passes through the sample: T = I/I0. Absorbance (A) is the logarithmic inverse: A = log(1/T) = -log(T) = log(I0/I). Absorbance is preferred in analytical work because it follows the linear Beer-Lambert law and has a wider useful range than transmission.
How do I choose the optimal wavelength for my analysis?
Scan the sample across the UV-Vis range (190–900 nm) to generate an absorption spectrum and identify the wavelength of maximum absorption (lambda max). For quantitative analysis, use this wavelength to maximize sensitivity. If interference exists at lambda max, use an alternative peak if present, or use derivative spectroscopy or principal component analysis to resolve overlapping spectra.
What causes nonlinearity in the Beer-Lambert law?
Deviations from linearity typically occur at high absorbance (A > 1.5–2), where instrumental errors become significant, or when the analyte associates (forms dimers or complexes) as concentration increases. Staying within the recommended absorbance range (0.1–1.0) ensures linearity. High concentrations can be remedied by diluting the sample.
Can UV-Vis spectrophotometry be used for kinetic measurements?
Yes. Kinetic spectrophotometry measures changes in absorbance over time, allowing determination of enzyme kinetics, reaction rates, and binding kinetics. A stopped-flow spectrophotometer rapidly mixes reagents and immediately measures the absorbance change, enabling analysis of fast reactions (millisecond timescale).
What is derivative spectroscopy, and when should I use it?
Derivative spectroscopy calculates the first (dA/dλ) or second (d²A/dλ²) derivative of the absorbance spectrum with respect to wavelength. This technique can resolve overlapping peaks, reduce background noise, and enhance selectivity when a single wavelength is ambiguous. It is particularly useful for analyzing complex samples with multiple chromophoric species.
Sources
- Beer, A. (1852). Bestimmung der Absorption des rothen Lichts in farbigen Flussigkeiten. Annalen der Physik und Chemie, 86(5), 78–88. DOI: 10.1002/andp.18521620505 ↗
- Skoog, D. A., West, D. M., Holler, F. J., & Crouch, S. R. (2014). Fundamentals of Analytical Chemistry (9th ed.). Cengage Learning. ISBN: 978-1133170960
- Knowles, A., & Burgess, C. (Eds.). (1989). Practical Absorption Spectrometry (2nd ed.). Chapman and Hall. ISBN: 978-0412273208
How to cite this page
ScholarGate. (2026, June 3). UV-Vis Spectrophotometry. ScholarGate. https://scholargate.app/en/analytical-chemistry/uv-vis-spectrophotometry
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
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