| After CSI technicians have recovered suspicious | | | | substance and compare it to another. |
| material evidence like a possible accelerant at a crime | | | | The mass spectroscope is a machine that showers a |
| scene suspected as arson, they bring it back to the | | | | compound with a beam of high-energy electrons that |
| crime lab and look at the evidence more closely. The | | | | cause the separation of that compound. The resulting |
| scientific procedures used in an actual crime lab are | | | | individual fragments then pass through an electric or |
| similar to those you see on the CSI TV shows. In | | | | magnetic field that separates them according to their |
| this article, we will discuss some of the procedures | | | | individual masses. The pattern of fragmentation of |
| used when CSI technicians examine evidence in | | | | the unknown compound is then compared via |
| closer detail. | | | | computer to known patterns of fragmentation on |
| In a scientific crime lab, the following procedures are | | | | record and scrutinized by a technician with the hope |
| used to analyze compounds up close: | | | | of determining a consistency that unveils the |
| - Gas chromatography | | | | composition of the unknown compound. |
| - Mass spectroscopy, and | | | | The GC and MS can be used together. This |
| - Infrared spectrophotometry | | | | conglomerate is called a gas chromatograph-mass |
| No doubt, you may have heard of these | | | | spectrometer. The GC feeds each separated |
| terminologies when watching your favorite CSI | | | | gaseous substance into the MS which in turn |
| program. | | | | determines the substance's mass spectrum. Just |
| Gas chromatography (GC) is a method used to | | | | about any substance can be identified using this |
| identify what a compound is and how far each part | | | | combination. |
| of it moves through an inert gas, or noble gas. GC | | | | Finally, infrared spectrophotometry (IR) is a technique |
| very quickly separates mixtures of compounds into | | | | used to identify the absorption spectrum of a |
| individual parts in this way. | | | | compound since each compound has a unique infrared |
| The way GC is performed is that a lab technician | | | | absorption spectrum. This method determines the |
| injects a liquid sample into one end of the column | | | | amount of infrared light absorbed by the compound |
| that is heated and vaporized. The vapor enters the | | | | of interest and results in a chemical fingerprint of that |
| column and flows with the moving inert gas until it | | | | same compound. |
| reaches another gadget called a detector. Different | | | | IR can also be used in conjunction with GC, and the |
| compounds move at different speeds and thus | | | | GC-IR combination very quickly gives results that are |
| separate from each other. During this change, the | | | | just as accurate as the ones given by the GC-MS |
| individual compounds arrive at the detector at | | | | combination. |
| different times. It is a scientific marathon for individual | | | | Interpreting the Results |
| compounds. The detector then signals another | | | | Even though technicians can not always determine |
| gadget called a recorder that prints a graph, called a | | | | the exact manufacturer of a given compound, a |
| chromatograph, that denotes each of the | | | | comparative analysis between the unknown |
| compounds detected. Many times, the result of the | | | | compound and those taken from suspected areas |
| GC are needed by technicians to determine the | | | | may help them trace the unknown sample to a |
| composition of the unknown substance. If they need | | | | particular gas station or hardware store that sells the |
| more information, technicians can combine the results | | | | accelerant. |
| of the GC with the results of either infrared | | | | Though this particular investigative technique is not |
| spectrophotometry or mass spectroscopy. | | | | totally reliable, the investigative criminal scientist may |
| Mass spectroscopy (MS) is another technique used in | | | | be able to say that it came from a particular source. |
| a crime lab to determine a substance's chemical | | | | The next time you watch any of the CSI shows, |
| makeup. Since no two substances have the exact | | | | you will have better knowledge of what some of |
| same chemical makeup, or chemical fingerprint, this | | | | these techniques are used for whenever you hear |
| gadget can be used to determine the makeup of one | | | | the terminologies we have discussed. |