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1、Gas Chromatography and Mass Spectrometer uses,Definitions:,Gas Chromatograph-a machine used to separate mixtures into each component using various detectors. Mass Spectrometer-an analysis that identifies and measures the particles mass Isotope-any of two or more species of atoms of a chemical elemen
2、t with the same atomic number and nearly identical chemical behavior but with differing atomic mass or mass number and different physical properties GC/MS-Gas chromatography and Mass spectrometry,Uses for GC/MS:,Did you know that mass spectrometry is used to. Detect and identify the use of steroids
3、in athletes Monitor the breath of patients by anesthesiologists during surgery Determine the composition of molecular species found in space Determine whether honey is adulterated with corn syrup Locate oil deposits by measuring petroleum precursors in rock Monitor fermentation processes for the bio
4、technology industry Detect dioxins in contaminated fish Determine gene damage from environmental causes Establish the elemental composition of semiconductor materials Check monitor wells to determine where the gas contamination came from. Was it naturally occurring from the earth or did some outside
5、 source contaminate it?,More GC/MS uses:,In the U.S. TV show CSI for example, GCs are used to rapidly identify unknown samples. medical, pharmacological, environmental, and law enforcement fields all use GC/MS,What a GC does:,Sample is prepared Sample is injected Carrier gas pushes the sample throug
6、h columnsI use 3 different type of columns on the GCs I run. Molecular Sieve, Capillary column, Hay Sep A column Sample is pushed to the detector and the components are identified.,GC Info:,Detectors used on our GCs: Thermal Conductivity Detector (TCD) and Flame Ionization Detector (FID) Computer so
7、ftware is used to quantize the peaks from the chromatography trace.,MS overview, cont.,The isotope-ratio mass spectrometer (IRMS) allows the precise measurement of mixtures of stable isotopes. The two most common types of IRMS instruments are continuous flow and dual inlet both done at Isotech. In d
8、ual inlet IRMS, purified gas (CO2 from prep benches or H2O converted to H+) obtained from a sample is alternated rapidly with a standard gas (of known isotopic composition) by means of a system of valves, so that a number of comparison measurements are made of both gases. The reference pulses of the
9、 same voltage is what makes the dual inlet more accurate and precise than conflo. In continuous flow IRMS, sample preparation occurs immediately before introduction to the IRMS, and the purified gas produced from the sample is measured just once. The standard gas may be measured before and after the
10、 sample or after a series of sample measurements (reference pulses). While continuous-flow IRMS instruments can achieve higher sample throughput and are more convenient to use than dual inlet instruments, the yielded data is of approximately 10-fold lower precision- but not ours because we rock :D,T
11、his is a picture describing how the IRMS works both on dual inlet and conflo. The purified component of interest is introduced to the MS where it hits the ion source. A tungsten filament in the source bombards the gas with electrons knocking off an electron and producing a positively charged ion. Th
12、e positively charged ion is then focused out of the source and down a flight tube where a magnet is used to bend the ions separating them into their different masses. The lighter mass ( mass 44 in this picture) will bend the most, whereas the heavier mass (mass 46) will bend the least. Faraday collectors are used to quantify the masses and Isodat software provides a ratio of Mass 44/45.,Mass Spec overview:,GC trace from FID,GC trace TCD,
