1 / 22

Atomic Absorption Spectroscopy

Atomic Absorption Spectroscopy. Yash Purohit Block 4. AAS Uses. Measures the light absorbed by the atoms of a sample then compares it to a set of known standard concentration It used in different ways for different fields of work Mining:

bdwyer
Télécharger la présentation

Atomic Absorption Spectroscopy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Atomic Absorption Spectroscopy Yash Purohit Block 4

  2. AAS Uses • Measures the light absorbed by the atoms of a sample then compares it to a set of known standard concentration • It used in different ways for different fields of work • Mining: • Measure the concentration of metals such as gold to know whether to mine there • Food and drug inspections • To measure concentration of certain harmful things in food and drugs

  3. AAS Uses Continued • Environmental: • It is also used in air samples to see if lead or mercury is present • Petrochemical: •  analyzing products for metals and other substances that can have adverse affects such as oil and gas • Pharmaceutical: • For quality control so not to much of a substance is put into the drug

  4. How It Works • Sample is introduced into the machine • Nitrous oxide flows into the machine where the solution is, in the nebuliser, and creates a vacuum • The solution in that vacuum is converted into a gas • With the gas is forced into the flame, which is a really high temperature (2000°C) • This atomizes it and separates the particles • Now a light usually a hollow cathode lamp is shined into the center of the flame • Any light not absorbed is passed into the monochromator and detector

  5. Atomizers • Flame • Electro thermal • Vapor generation (cold and heated) • Plasma • Arc and spark

  6. Types of Data • Even with small amounts of the element over 65 different elements can be detected • Using the wavelengths absorbed and set absorbance spectrum we can find out the element (qualitative) • The concentration of an element can also be determined by using known standard concentration solutions (quantitative) • You would use 5 known concentration solutions and get their absorbance then make a calibration curve • Next put the unknown to find the absorbance • Beer-Lambert law A=abc

  7. Relation to Forensic Science • Used in a variety of analyses in forensics science • Like in food poisoning cases you could us AAS to check of toxic material. • For example chocolate it is used to find toxic cadmium • You would take small but representative sample of the food would need to be turned it into gas by heating it then put in the machine • Different wavelengths of light will be shined at the gas and flame

  8. Relation to Forensic Science continued • Also gunshot residue some one suspected of shooting could have there hand and clothes swabbed to check for high amounts of lead and other elements found in gun powder • Similar to the food the gun powder would have to be turned into a gas then put in the machine • Different wave lengths will be sent to see which is absorbed • Since each element is different based on which are absorbed you can figure out the element

  9. Relation to Forensic Science continued • Very important for forensics science is soil samples. • If soil is found on a person AAS can be used to find the elements that are most abundant in the soil • Then it will be traced to a location with similar amounts of the element in the soil. • Obviously done through comparing the sample you have to others taken

  10. Real Life Case Use • Suicide case of a 52 year old women • She took some poison that was said to have arsenic trioxide (As2O3) • Blood, bile and liver samples were taken from the dead women • Then using AAS the samples were analyzed to find the elements in the samples • After that, reference sample solutions were made with known amounts of arsenic trioxide in them • Calibration curve was made to then find concentration of the unknown

  11. Chemical Principles • The solution is put into the machine where it under goes a phase change and only the elements remain • After they are forced into the flame a light is shined at the center where the free atoms are • The electrons then absorb certain wavelengths and go from the ground state to higher states • Since every element has a different absorption spectrum that is just for that element you can figure out which element or elements are present

  12. Safety • When starting the flame be careful it is extremely hot and make sure to close the latch in front of the flame • Gases being used in vacuum like nitrous oxide when broken down can help start fires • Do not view the flame directly or you could go blind • Make sure vents are properly working so the gas can removed • When using AAS starting fires and causing explosions are the biggest safety issues.

  13. Interference • Machine interference could be the spectral lines of two or more elements are over lapping one another • In this case you would not be able to find the elements present • Chemical interference occurs when analyte do not atomize completely • For example an analysis for a sample of calcium you have Calcium Chloride and Calcium Sulfate in a sample one atomizes but the other does not, the absorbance reading is worthless

  14. Limitations • Basically is only good for metals, non-metals have to be analyzed indirectly • Only a bit over 60 elements on the periodic table will be rapidly detected • Multiple elements cannot be detected at once • For most flame atomic absorption the detection is between 1microgram per liter and 3000microgram per liter • Do not seem like to much but compared to others the samples are big • There is really no bias for this

  15. Advantages • Machine is fairly easy to use after the sample has been put in • Very few interferences • Since there are different atomizers different types of sample can be taken • Solids, liquids, and gases • Some machines are fasters than other and other get more accurate data • High precision data regardless of which type is used

  16. Disadvantages • For flame atomic absorption only solutions can be analyzed • Graphite furnace atomic absorption has low precision • For all types a calibration curve needs to be formed for quantitative analysis • One element has to be determined at a time because each requires a special light source

  17. "AAS Theory." AAS Theory. N.p., n.d. Web. 31 Mar. 2015. • "Atomic Absorption Spectroscopy." Atomic Absorption Spectroscopy. N.p., n.d. Web. 31 Mar. 2015. • "Atomic Absorption Spectroscopy." Chemical & Engineering News 60.8 (1982): 18. Web. 31 Mar. 2015. • "Atomic Absorption Spectroscopy Learning Module." Atomic Absorption Spectroscopy Learning Module RSS. N.p., n.d. Web. 31 Mar. 2015. • Norheim, Gunnar. Arsenic Determination in Autopsy Material Using Atomic Absorption Spectroscopy. N.p., n.d. Web. 31 Mar. 2015. • "Tecmec Ltd - How Does Atomic Spectroscopy Work?" Tecmec Ltd - How Does Atomic Spectroscopy Work? N.p., n.d. Web. 31 Mar. 2015.

More Related