What Is UV-VIS Analysis?
A UV-VIS spectrophotometer measures how much light in the ultraviolet and visible region a solution absorbs. Absorbance is directly proportional to concentration, per the Beer-Lambert relationship.
Purpose of UV-VIS Analysis
The purpose is to determine the concentration of light-absorbing compounds quickly and at low cost. Combined with colour-forming reagents, substances that do not absorb on their own also become measurable.
Which Products Is UV-VIS Analysis Applied To?
- Parameters such as nitrate, phosphate, COD in drinking and wastewater
- Active ingredient assay in pharmaceutical products
- Colour and additive measurement in food and beverages
- UV filter concentration in cosmetics
- Enzyme and protein concentration measurements
In Which Sectors Is UV-VIS Analysis Used?
Standards Related to UV-VIS Analysis
- European Pharmacopoeia 2.2.25 (absorption spectrophotometry)
- ISO 7887 (water quality — determination of colour)
- ISO 6060 / ISO 15705 (chemical oxygen demand)
UV-VIS Analysis Conditions
- Dalga boyu
- Absorption maximum of the analyte; defined in the method
- Bathtub
- Quartz in the UV region, glass or plastic in the visible region
- linear range
- It is studied in the absorbance range where Lambert-Beer is valid.
- Blind
- Zeroing is done with solvent or reagent blank
Equipment for UV-VIS Analysis
- UV-VIS spectrophotometer
- Quartz and glass cuvettes
- Automatic cuvette changer
- Temperature-controlled cuvette holder (for kinetic measurements)
Sample Requirements for UV-VIS Analysis
- The sample must be a clear solution; turbidity distorts the result
- Filtration or centrifugation is applied if required
- Diluted if concentration is above the linear range
- A few millilitres of sample is generally sufficient
Duration of UV-VIS Analysis
A single measurement takes seconds. Sample preparation and the waiting times of colour-forming reactions determine the total duration.
UV-VIS Analysis Procedure
- 1The sample is dissolved, filtered if required, and diluted.
- 2A colour-forming reagent, if used, is added and the defined waiting time is observed.
- 3The instrument is zeroed with the blank solution.
- 4The absorbance of the calibration solutions is measured.
- 5Sample absorbance is read.
- 6Concentration is calculated from the calibration curve.
UV-VIS Analysis Acceptance Criteria
Acceptability of the result is determined by comparison with values in the pharmacopoeial monograph, discharge limits, or product specification.
Evaluation of Results
The measurement is valid only within the range where the Beer-Lambert relationship is linear. Deviation begins at high absorbance values; in that case a result taken without dilution is not reliable.
UV-VIS Analysis Report
- Sample description, receipt date and laboratory number
- Method applied and reference standard, if any
- Instrument and measurement conditions
- Sample preparation steps
- Measurement results and units
- Measurement uncertainty (if requested)
- A statement that the results relate only to the sample submitted for testing
Accreditation
EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.
Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.
Scope and authorisationsRelated Regulations
- Water Pollution Control Regulation
- Regulation on Water Intended for Human Consumption
- European Pharmacopoeia monographs
Pages Where This Method Is Used
Analytical Methods — What Does This Group of Methods Do?
The section below describes the field that the UV-VIS Analysis test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.
Analytical method pages are pages about a MEASUREMENT TECHNIQUE rather than about a test. The difference matters: "salt spray testing" is a test and answers one question; "ICP-MS" is a technique and is used in dozens of different tests. Sometimes the user is looking not for the test but for the technique — because the method name is what appears in their specification.
This distinction becomes decisive in choosing a laboratory. When a customer asks for "heavy metal analysis", the real question is by which technique it will be done: XRF is fast and non-destructive but does not distinguish compounds; AAS is economical for a single element; ICP-OES screens multiple elements; ICP-MS sees trace levels. The same sample gives results with different detection limits and different uncertainties across the four techniques.
Method selection is made against three criteria. DETECTION LIMIT: is the concentration sought within the range the method can see? MATRIX COMPATIBILITY: is the sample matrix (plastic, food, soil, metal) one the method can handle, and is pre-treatment required? SPECIFICATION LINK: does the product standard or legislation mandate a particular method? The third often overrides the first two — the specification binds the method.
Method pages build a CHAIN. A technique is linked to the test pages where it is used, to the standards those tests rest on, to the legislation those standards are tied to and ultimately to market access regimes. The example chain in the source document works like this: XRF → metal analysis → RoHS compliance → heavy metal restriction → coating pages. Whichever link the user enters from, they reach the others.
Sample preparation is the invisible half of the result in this family and is a greater source of error than the technique itself. The digestion method, degree of grinding, extraction solvent and dilution ratio change the result markedly. The same sample on the same instrument gives a different result with different preparation; the definition of the method therefore covers preparation too.
Calibration and verification are the third determining component. An instrument is calibrated with certified reference material, the calibration curve is verified periodically and a control sample is run in each batch. Without these steps, a number produced is not traceable even if the instrument is working correctly.
Method groups in this field
Elemental analysis
ICP-OES, ICP-MS, AAS and XRF. They differ in detection limit, matrix tolerance and multi-element capacity.
Chromatography
GC, GC-MS, HPLC, LC-MS/MS and ion chromatography. It separates a mixture into its components and measures each separately.
Spectroscopy
FTIR, Raman, UV-Vis and optical emission. For material identity, functional group identification and alloy composition.
Thermal analysis
DSC, TGA, DMA and dilatometry. Transition temperatures, composition, decomposition and dimensional behaviour.
Microscopy and imaging
Optical microscopy, SEM-EDS, radiography and tomography. Structure, defects and elemental distribution.
Classical (wet) chemistry
Titration, gravimetry and colorimetry. Used as a reference method and in confirming instrumental results.
Commonly confused in this field
- XRF is a screening tool; it sees elements and does not distinguish compounds. A decision on a restricted compound requires confirmation by wet chemistry.
- The phrase "not detected" is not proof of absence; it is read together with the detection limit of the method.
- The specification binds the method. A technically better method is not accepted if the specification calls for another.
- Sample preparation is part of the result; a report that does not state the preparation is not reproducible.
- Results obtained by different techniques cannot be compared directly; their detection limits and uncertainties differ.
- A method page is not a test page; which method applies to which test comes from the product standard.
Which decisions these results support
- Matching the method written in the specification to the laboratory's scope
- Method selection according to detection limit and matrix compatibility
- Confirming an instrumental result with a reference method
- Eliminating deviations arising from sample preparation
Related Tests
Frequently Asked Questions About UV-VIS Analysis
Can a turbid sample be measured?
No. Turbidity scatters light, artificially raising absorbance. The sample must first be filtered or centrifuged.
Can a single component be measured in a mixture?
Only if the other components do not absorb at the same wavelength. If there is interference, a chromatographic method is required.