Atomic Absorption Spectroscopy

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

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

8. 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

10. 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

11. 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

12. 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

13. 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

14. 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

16. 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.

17. 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

18. 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

19. 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

20. 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

22. "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.