[Instrumentation (SOURCES OF RADIATION AND MNOCHROMATOR)]

1. CALCUTTA INSTITUTE OF PHARMACEUTICAL TECHNOLOGY & ALLIED HEALTH SCIENCES INSTRUMENTATION (SOURCES OF RADIATION, MONOCHROMATOR) PRESENTED BY:- NAME:- BINAY PATHAK CLASS:- B.PHARM SEC:- B ROLL:- 15901919106 SUBJECT:- PHARMACEUTICAL ANALYSIS SUB. CODE:- PT711 REG. NO.:- 012889 OF 2019-20

2. INTRODUCTION Spectroscopy is the study of interaction between matter(ie. Molecule, atoms, nuclei) and radiated energy(ie. Electromagnetic radiation). The most important thing of such interaction is that the energy absorbed or emitted by the matter in fixed amounts called “Quanta”. The types of spectroscopy further carried out as:- 1. Atomic Spectroscopy 2. Molecular Spectroscopy UV Visible Spectroscopy (UV-Vis or UV/Vis) refers to absorption spectroscopy or reflectance spectroscopy in the ultraviolet-visible spectral region. Ultraviolet-Visible (UV-VIS) Spectroscopy is an analytical method that can measure the analyte quantity depending on the amount of light received by the analyte. Ultraviolet / Visible Area (UV-VIS) measurements span wavelengths from around 200 nm to 800 nm. UV-vis spectroscopy is a cost-effective, simple, versatile, non-destructive, analytical technique suitable for a large spectrum of organic compounds and some inorganic species. As a function of wavelength, UV-vis spectrophotometers measure the absorption or transmission of light that passes through a medium.

3. INSTRUMENTATION A Spectrophotometer is a device which detects the percentage transmittance of light radiation when light of certain intensity and frequency range is passed through the sample. • This instrument compares the intensity of the transmitted light with that of the incident light. • The modern ultra-violet–visible spectrometers consist of light source, monochromator, detector, amplifier and the recording devices. • a) Tungsten Filament lamp (Tungsten filament lamp is particularly rich in red radiations i.e., radiations with wavelength 375 mμ). b) Hydrogen-deuterium discharge lamp (The intensity of the deuterium source falls above 360 mμ) which cover the whole of the UV- Deuterium Lamp The most suitable sources of light are : -- • discharge visible region.

4. SOURCES OF RADIATION There are two classes of radiation sources used in spectrometry :- 1. Continuum Sources:- Emit radiation over a broad wavelength range and the intensity of the radiation changes slowly as a function of wavelength. a) Deuterium Lamp is the common UV source. b) Tungsten Lamp is the most common Visible source. c) Glowing inert solids are common sources for IR instruments. 2. Line Sources:- Emits a limited number of lines or bands of radiation at specific wavelengths. It is used in atomic absorbtion spectroscopy. Types of Line sources are:- a) Hollow cathode lamps b) electrodeless discharge lamps. c) Lasers – Light amplification by stimulated emission of radiation.

5. I. Continuum Sources a) Deuterium lamp:- A deuterium arc lamp (or simply deuterium lamp) is a low-pressure gas-discharge light source often used in spectroscopy when a continuous spectrum in the ultraviolet region is needed. •Electrical excitation at low pressure (<0.5 torr) , low voltage (~40V DC). •Forms molecular excited state that undergoes dissociation and Photoemission. •Provides continuum from ~160 -380 nm. • It requires separate power supply. • It has shorter life time and expensive to replace.

6. b) Tungsten Lamp :- Types of lamp- a) Tungsten filament lamp Advantages - inexpensive, reliable and stable sources of visible radiation (350-8—nm), longer life Limitations - Evaporating tungsten on the glass envelope reducing the output. b) Tungsten halogen lamp – It is same as tungsten filament lamp but the filament in a halogen fitted quartz envelope. Advantages – It prevents tungsten evaporation but more expensive than filament lamp.

7. 2. Line sources :- a). Hollow Cathode Lamp – Cathode is coated with atom of interest – Tube is filled with Ar or Ne – High voltage ionizes gas, charged ions are accelerated toward electrodes • Produces sputtering of atoms (ground and excited) • Excited atoms emit light at atomic lines – Design of HCL results in redepostion of metal atoms onto electrodes – recycling – Need to avoid excessively high potentials. • Line broadening (Doppler) • Self–absorption

8. b). Electrodeless Discharge Lamp • A small amount of the metal or salt of the element for which the source is to be used is sealed inside a quartz bulb. This bulb is placed inside, self-contained RF generator. When power is apllied to the driver, an RF field is created. • The coupled energy will vaporize and excite the atoms inside the bulb, causing them to emit their characteristic spectrum. • They are typically much more intense and, in some cases, more sensitive than comparable hollow cathode lamps. Hence better precision and lower detection limits where an analysis is intensity limited. • EDL are available for a wide variety of elements, including Sb, As, Bi, Cd, Cs, Ge, Pb, Hg, P, Rb, Se, Te, Th, Sn and Zn. • Construction Of An EDL

9. c). Lasers :- • Light amplification by stimulated Emission of Radiation. • Produce specific spectral lines. • Used when high intensity line source is required. Types Solid state lasers :- Ex - Ruby laser, Neodymium: YAG laser Gas lasers :- Types- Neural atom lasers(He & Ne) Ion lasers(Ar+ & Kr+) Molecular lasers(CO2& N2) Excimer lasers.(ArF & XeCl) Tunable lasers Semiconductor lasers • • • • Tunable laser Semiconductor laser

10. MONOCHROMATOR Monochromator is a device which is used to resolve polychromatic radiation into its individual wavelength and isolates these wavelengths into a very narrow band. This device produces light radiation of only particular(single) wavelength. Thus, light of single or only one wavelength is called monochromatic radiation. A monochromator consists of:- • An entrance slit which admits polychromatic radiation from the source. • A collimating device which is either a lens or a mirror. • A dispersion device, prism or grating which resolve the radiation into its individual components. • A focusing lens or mirror; and an exit slit.

11. TYPES OF MONOCHROMATOR a) Prism Monochromator • Dispersion by prism depends on refraction of light which is wavelength dependent. Violet color with higher energy(shorter wavelength) are diffracted or bent most while red light with lower energy(longer wavelength) are diffracted or bent least. • As a result, the polychromatic white light is dispersed to its individual colors. •

12. b) Grating Monochromator :- • A fine beam of the light from the source falls on a concave mirror by an entrance slit. These rays fall on a reflection grating where different wavelengths are reflected at different angles. • The dispersed radiation is then directed to an exit slit. • The range of wavelengths isolated through the monochromator is determined through the extent of dispersion through the grating and the width of the exit slit. • The orientation of the reflection grating directs only one narrow band wavelengths, λ2to the exit slit of the monochromator. • Rotation of the grating within a predetermined way could be used to acquire the desired wavelength λ1to pass through the exit slit. •

13. REFERENCE ❑ Sharma Y.R. Ultraviolet and visible spectroscopy in; Elementary Organic spectroscopy, 1 ed., S.Chand & Company Ltd ., New Delhi, 2004; 9-60. ❑ Dr. Manish Kumar, Uv-Visible spectroscopy and fluorimetry; A Textbook of Instrumental Methods of Analysis, SIA publishers & Distributors Pvt. Ltd, Hyderabad 2020; 1.23-1.24. ❑ https://documen.site/download/lecture-2-uv-instrumentation_pdf ❑ https://www.slideshare.net/sanashaikh106/spectroscopy-sources ❑ https://www.slideshare.net/tejasrigopi/atomic-absorption-spectrophotometer-38678151