Lecture 2_Emission Spectroscopy PDF

Biomedical Techniques CLSB-222  EMISSION SPECTROSC OPY Emission Spectroscopy A method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample....

Biomedical Techniques CLSB-222  EMISSION SPECTROSC OPY Emission Spectroscopy A method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. - Atoms are thermally excited to higher electronic Energy The principle of levels using exciting source (e.g. Flame) , and then relax back to lower electronic energy levels by emitting radiation in the Atomic Emission UV-visible region. Spectroscopy - The emitted radiation is detected and used to determine which elements are present, and their concentration. Used as standard method for the metal analysis tp://www.pci.tu-bs.de/aggericke/PC4/Kap_I/aes.htm Atoms excitation and emission  Emission Spectroscopy: Applications Flame photometry is used mainly for the determination of alkali metals and easily excited elements (Na, K, Li, Ca, etc.) particularly in biological fluids and tissues Useful in determination of alkali and alkaline earth metals Used in determination of lead in petrol Used in determination of calcium and magnesium in cement Emission Spectroscopy: Disadvantages EQUIPMENT IS PROCEDURE IS MORE TIME HIGHER MORE EXPENSIVE MORE CONSUMING OPERATING COMPLICATED COSTS Luminescen ce  What is luminescence? Luminescence is a general term for the emission of light from a cool object. (In contrast to, e.g., incandescence – the emission of light from a hot piece of metals such as the filament in a light bulb.) There are many examples of naturally occurring luminescence. Most of these fall into one of 3 categories: Phosphorescence: Absorption and slow re-emission of light. Most commonly observed in minerals. Fluorescence: Absorption and fast re-emission of light. Seen in deep sea organisms and some insects and plants. Chemiluminescence: Emission of light driven by a chemical reaction. The most common form of natural luminescence (often called “bioluminescence”). Seen in aquatic organisms, insects and plants.  Phosphorescence Certain minerals will glow in the dark when exposed to ultraviolet (UV) light. Some of them continue to glow even after the ultraviolet light is turned off. This “slow” re-emission of light is known as phosphorescence. The first phosphorescent mineral was reported in the early 1600s. These minerals, or “inorganic phosphors” have many interesting uses – for example, they are used in making the cathode ray tubes still used in older color televisions.  Fluorescence Like phosphorescence, fluorescence involves absorbing and re-emitting light. However, fluorescence is very fast, and is disappears as soon as there is no more light to absorb. An interesting example of natural fluorescence is the exoskeleton of scorpions – scorpions glow under UV light! People are still arguing about whether this fluorescence has a biological role, or if it is just a coincidence. For people who like to collect scorpions, it makes them easy to find at night with a portable UV lamp  Chemiluminescence Chemi-luminescence is the generation of light by a chemical reaction. This is the most common form of luminescence in living organisms. Insects like fireflies use chemi-luminescence to attract their mates, Deep sea fish like the Anglerfish use it to lure prey close to their mouth Microorganisms use it to signal distress. Recent studies suggest that humans may give off light too, although this is controversial.  Spectrofluorometers Measures the fluorescence signature of an analyte in a sample based on its specific excitation and Emission wavelengths. Fluorescence signature can be correlated to the concentration level of the analyte in the sample A Spectrofluorometer can be used in : Basic and Applied Research Biofuels Analysis Medical Diagnostics Plasma\Monitoring and Polymer Analysis Spectrofluorometer Versus spectrophotometers Spectrofluorometer measures fluorescence. Spectrophotometer measures absorbance/transmittance. https://www.youtube.com/watch?v=HMfcFYNRidc