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Jorge Pinho Alfredo Fuentes.  It is used to identify molecules based on their masses and how molecules fall apart into fragments  The molecules are.

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Presentation on theme: "Jorge Pinho Alfredo Fuentes.  It is used to identify molecules based on their masses and how molecules fall apart into fragments  The molecules are."— Presentation transcript:

1 Jorge Pinho Alfredo Fuentes

2  It is used to identify molecules based on their masses and how molecules fall apart into fragments  The molecules are entered in a vacuum system in the vapor phase  The molecule is shot with a beam of high-energy electrons to split the molecule into ions  They pass a magnetic field used to deflect their straight path causing them to curve based on their mass  The molecules will collide with the detector at certain positions based on their mass  This method can be used to determine the chemical composition of an unknown found on the crime scene, making it relevant to forensics science and crime labs  The mass spectrometer is usually very fast, convenient, reliable, and often readily available in forensic labs

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4  Evidence that it analyzes are drug related samples, powders and crystals, and toxicology samples  Some pieces of evidence can be urine, blood, or powders like cocaine

5  A internal standard solution is prepared with methanol or acetonitrile, based on the solubility of the solute: the blood, urine or powder; then the internal standard is mixed with the samples  The solution is placed in a vacuum system, where it is converted into the vapor phase  The molecules then collide with a beam of high-energy electrons which, stripping off an electron making the molecule a positive ion  Electrical current is then applied to the ions to accelerate them along the tube  It then passes a magnetic field which curves the path of the ions, lighter ions having a higher degree of deflection than heavier ones  The ions then collide with the detector placed at the end of the tube, the mass is then determined by the position the ions land

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7  High Voltage  The mass spectrometer generates low levels of radio frequency energy, which could interfere with devices such as pacemakers or a radio receivers.  Wear gloves, goggles, and lab coats.  The hazardous chemicals identified by the Mass spectrometer can detrimental to one’s health.

8  Chemical leaks may present a hazardous safety concern.  Must be used indoors in appropriate conditions according to the instructions.  Avoid harmful chemicals from contact of the mass spectrometer that can potentially contaminate the instrument.

9 Advantages  The Mass Spectrometer is considered one of the most important tools in a crime laboratory.  It can separate complex mixtures with great precision.  Can distinguish small concentrations.  High Sensitivity Disadvantages  Usually is used together with a GC.  Not well suited for pulsed ionization methods.  Usually larger and higher cost than other methods of analysis.

10  High dynamic range  High sensitivity  High resolution  It can detect substances one-millionth of a gram.  High Precision

11  safety-guide-eng.pdf safety-guide-eng.pdf  https://www.princeton.edu/chemistry/macmillan/group- meetings/SL-mass%20spect.pdf https://www.princeton.edu/chemistry/macmillan/group- meetings/SL-mass%20spect.pdf   Spencer, T. James, “An Introduction to Forensic Science: The Science of Criminalistics”, Ch 12.5  10.pdf 10.pdf  file:///C:/Users/Alfredo/Downloads/540dc3d00cf2f2b29a3a054a.p df file:///C:/Users/Alfredo/Downloads/540dc3d00cf2f2b29a3a054a.p df  Slides 2-6 done by Alfredo, Pictures and slides 7-10 done by Jorge


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