UV-Visible spectroscopy Presentation.

This presentation introduces the principles, components, and applications of UV-Vis spectroscopy. It demonstrates the significance of UV-Vis spectroscopy in science and industry through real-world examples. This work has been prepared as a first-year university assignment.

1. Ultraviolet–visible spectroscopy Tibet Ş. - Yeditepe University Your personal information (full name, school number, school name, etc.)

2. TITLES 1- Introduction to UV-Vis Spectroscopy 2- Historical Background 3- Principles & How It Works 4- Components of a UV-Vis Spectrophotometer 5- Applications and Observations in Science & Industry 6- Conclusion & Future Perspectives ●

3. Introduction to UV-Vis Spectroscopy ● Definition: UV-Vis spectroscopy measures the absorption and transmittance of light in the ultraviolet and visible range. ● Importance: Used in chemical analysis, pharmaceuticals, environmental science, and material studies. ● Objective: Understanding its principles, instrumentation, and real-world applications.

4. Fundamental Discoveries and Theoretical Foundations - 1666 – Isaac Newton’s Prism Experiment - 1801 – Johann Wilhelm Ritter and the Discovery of UV Light - 1814 – Joseph von Fraunhofer and Absorption Lines - 1852 – Gustav Kirchhoff & Robert Bunsen’s Flame Spectroscopy - 1852 – Beer-Lambert Law

5. ● The Birth of Modern UV-Vis Spectroscopy 1941 – First Commercial UV-Vis Spectrophotometer - Arnold O. Beckman 1947 – First Recording UV-Vis Spectrophotometer - Applied Physics Corporation 1954 – First Double-Beam Spectrophotometer - Howard Cary 1963 – Advances in Double-Beam Spectrophotometers - JASCO

6. 1969 – First Variable-Wavelength HPLC Detector - Cecil Instruments 1979 – First Diode-Array UV-Vis Spectrophotometer - Hewlett-Packard (HP) 1980 to present – Microprocessor Integration - UV-Vis spectrophotometers started incorporating computers and software , enhancing data processing and automation. - AI-driven software and advanced analytics improved spectral interpretation and accuracy

7. Principles Light Absorption: Molecules absorb UV/Vis light, causing electronic transitions. ●

8. UV-Vis Spectroscopy in the Electromagnetic Spectrum: "Only UV-Vis light carries enough energy to move electrons to higher molecular orbitals — that's why electronic transitions occur only in this region. "

9. Electronic Transitions: π → π* (Conjugated double bonds), n → π* (Lone-pair transitions), σ → σ* ( very high energy, in the UV region) "Only π → π* and n → π* transitions are typically detected in standard UV-Vis spectroscopy."

10. Beer–Lambert Law: " "Beer's Law describes the relationship between absorbance and concentration." "It is a fundamental principle for quantitative analysis in UV-Vis spectroscopy." ●

11. How It Works ● I ₀ : Incident light intensity ● I: Transmitted light intensity

12. From Light to Data (What Do We Measure): 1. What is Measured First? → Transmittance (T%): 2. First Graph: Transmittance vs. Concentration "This graph shows how the percentage of light passing through the sample (transmittance) decreases as the concentration increases."

13. 3. Then Transmittance is Converted to Absorbance: “We convert transmittance to absorbance because absorbance has a direct, linear relationship with concentration. This makes it ideal for quantitative analysis using Beer’s Law.” ● 4. Final Graph: Absorbance vs. Concentration: -This graph is used to create a calibration curve to determine unknown concentrations.

14. 5. Other Graph Types in UV-Vis Spectroscopy: Absorbance vs. Wavelength (λ): Absorbance vs. Time: “In the spectrophotometer, the wavelength is selected by a monochromator, which isolates a specific wavelength from the light source before it reaches the sample.” Used for reaction monitoring (kinetics)

15. Components of a UV-Vis Spectrophotometer

16. Light Source: deuterium lamps (UV) region: 200–400 nm tungsten-halogen lamps (visible) region: 400–800 nm ● Why Not Just One Lamp? ● ● Because no single lamp can cover both UV and visible regions efficiently . That's why UV-Vis spectrophotometers often use two lamps and switch between them depending on the selected wavelength.

17. Monochromator: "The monochromator selects a single wavelength from the broad spectrum of light emitted by the source." 1 - Entrance Slit: "Narrows the incoming beam to improve resolution."

18. 2 - Dispersing Element (Prism or Grating): 3 - a) Wavelength Selector (Rotating System): "Separates the incoming light into its component wavelengths." "Older UV-Vis instruments used prisms, but most modern spectrophotometers use diffraction gratings in their monochromators due to better wavelength resolution and accuracy." "The wavelength selector is a rotating system that adjusts the angle of the grating or prism to isolate a specific wavelength for measurement."

19. 3- b) Filters: 4 - Exit Slit: "The light that passes through the exit slit is called monochromatic light — a single, narrow wavelength selected by the monochromator." "Filters do not require a dispersing element because they already transmit only a specific wavelength or narrow band of light. Unlike gratings or prisms, filters isolate wavelengths directly without separating the full spectrum."

20. Beam Splitter: "A beam splitter is an optical device that divides a single beam of light into two separate paths, usually for simultaneous reference and sample measurements."

21. Sample Holder (Cuvette): "The cuvette holds the liquid sample. Light passes through it to measure absorbance." "Quartz cuvettes are required for UV measurements because regular glass absorbs UV light." "The 1 cm path length is standard and directly affects absorbance according to Beer’s Law." Different materials are used depending on the wavelength range: ● ● Quartz → for UV light (190–400 nm) Glass or Plastic → for visible light (400–800 nm)

22. Detector: "The detector measures the intensity of transmitted light and converts it into an electrical signal. Different types of detectors are used depending on the system." 1.Photodiode ● ● ● Used in traditional systems Works with a rotating wavelength selector to scan one wavelength at a time Stable and cost-effective 2. Photodiode Array (PDA) ● ● ● ● Used in modern instruments Measures all wavelengths simultaneously Often part of an integrated unit with the monochromator Enables fast and full-spectrum analysis 3. Photomultiplier Tube (PMT) ● ● ● Extremely sensitive to low light levels Ideal for low-concentration samples Converts light to signal with amplification

23. Modern Detection: PDA-Based UV-Vis Systems: "Unlike traditional UV-Vis systems that scan one wavelength at a time, PDA-based spectrophotometers can measure all wavelengths simultaneously. This makes them much faster, more efficient, and better for real-time analysis."

24. Applications and Observations in Science & Industry 1. Pharmaceutical Analysis ● ● ● ● Purpose: To identify and quantify drug compounds. Application: Used for quality control and stability testing. Observation: Absorbance changes with concentration; λmax confirms identity. Common Graph: Absorbance vs. Concentration (Beer’s Law) 2.Environmental Monitoring ● ● ● ● Purpose: To detect and measure pollutants. Application: Used in water quality testing and environmental analysis. Observation: Higher absorbance indicates higher pollutant levels. Common Graph: Absorbance vs. Concentration

25. 3. Food & Beverage Industry ● ● ● ● Purpose: To control color and detect additives. Application: Used in quality control and dye identification. Observation: Color intensity correlates with absorbance. Common Graph: Absorbance vs. Wavelength 4. Chemical & Biochemical Research ● ● ● ● Purpose: To study molecular behavior and reactions. Application: Used for kinetics, enzyme activity, and DNA/protein analysis. Observation: Absorbance changes over time and at λmax. Common Graph: Absorbance vs. Time

26. 5.Industrial Quality Control ● ● ● ● Purpose: To ensure product consistency. Application: Used in color matching and impurity detection. Observation: Spectral changes reveal defects or deviations. Common Graph: Absorbance vs. Wavelength Absorption spectrum of malachite green (λ max 617 nm).

27. Conclusion & Future Perspectives Conclusion: ● "UV-Vis spectroscopy is a versatile, accessible, and widely used technique for analyzing chemical substances. Whether for identifying compounds, quantifying concentrations, or monitoring reactions, it offers fast, reliable, and non-destructive analysis." ● "Through various applications in pharmaceuticals, environmental monitoring, food science, and industry, UV-Vis plays a critical role in both research and quality control." Future Perspectives: ● "As technology advances, UV-Vis systems are becoming more compact, automated, and integrated with AI and cloud-based data analysis." ● "Future developments may allow real-time environmental monitoring, portable diagnostics in healthcare, and more precise detection of complex mixtures through advanced detector arrays and hybrid systems."