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 (As 2 O 3 )  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

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