GC-MS
Screening for any specific drug requires that it be separated from many more others. This exercise requires a specialized facility. GC-MS machine was introduced to take care of this situation. As a way to consider how the GC-component is set up we shall consider how it works in detecting the presence of some of the substances which can be termed as steroids. These are believed by athletes to improve their performance when used in combination with good diet. For instance we will look into how it operates to detect its presence by use of the ratio of testosterone (T) called epitestosterone (E). The ratio of T to E is measured to observe if it conforms to the normal 1:1. This ratio determination is done using the GC-MS. The ratio for T/E increases temporarily when T is taken, then it is used to determine whether T was abused. The users of T can be determined against those who don’t use by plotting T/E as a function of time over weeks or months. The values for non users should be stable. For users the value shoots up when T is used and then drops back down. The carbon skeleton of T is focused on by testers as a way of tightening T/E loopholes. This is because there exists a difference in Carbon content between synthetic and natural T.
Gas chromatography difference is detected is detected by a the technique of Carbon Isotope Ratio (CIR). The anabolic steroids which are present in urine are gotten and separated by GC. With the exit of T from GC, it passes through the combustion oven. At this stage pyrolysis converts every carbon atom into 13CO2 or 12 CO2.
The real GC system is very fast. It provides literally everything someone needs for the GC to be fast. These include an injection that is fast and at the same time automatic, it has inlets that are split as well as splitless. It has a 0.1mm columns of capillary and a detector that has very high speed, and the rate of data handling is very fast. It also has method translation software. One can switch easily to GC.
The setup and operation 2D GC is more reliable and used easily by combination of micro-fluidic and EPC technologies. It minimizes the efforts of the operator by calculating restrictions and pressures automatically. Improved accuracy and reliability is enhanced by reproducibility of retention time. The 2D GC is made available fully pre-configured by Agilent as the option that is standard.
Agilent columns and supplies can be optimized to enhance greater confidence in your GC results. Many GC columns and other accessories are manufactured and tested to rigorous Agilent specifications, under a quality system.
Mass spectrum (MS)
Mass spectrum charges the specimen molecule electrically in order to identify the substances. It accelerates them through a magnetic field where the molecules are broken into charged fragments hence facilitating detection of different charges. The mass of each fragment is displayed by a spectral plot. The person doing the test can use the mass spectrum of the compound to identify them qualitatively. These fragment masses are used by technicians as puzzle pieces to regroup the original mass of the molecule. From the mass of the fragments and the molecular mass, the identity of the specimen is determined from the reference data. The mass spectrum of each substance is unique. Provision of the correct output determines the parent mass.
Description of MS process
This description will largely concentrate on the use of large magnet mass spectrometer. These instruments contain a sample inlet, source of ionization, accelerator for molecule and a detector.This process requires a pure sample of gas. The inlet of the sample is maintained at very high of about 4000 C. This is to ensure that the sample stays at the gaseous state. After this the sample enters the ionization chamber. A high voltage beam of electrons is accelerated. Each fragment is charged and moves towards the accelerator individually. At the acceleration chamber the velocity of the charged particles increase as a result of the accelerating voltage. The voltage that is accelerating varies so as to cover a range of masses in order for the entire fragments to reach the detector.
When charged particles collide with the surface of the detector some electrons come from the surface of the detector accelerating towards the second surface resulting to generation of more electrons which bombard another surface. At the point of amplification of the original charge the charge is measured by the instrument and recorded.
The MS instrument produces an output by drawing peak arrays on a chart, called the mass spectrum. Whereby fragment mass is represented by each peak. The height of the peak increases with the increase in the number of fragments detected with a particular mass.
History of development of MS section
Over a period of time MS has benefited in nearly all segments of products. Key laboratory and applications have made it to grow fast. The single and triple quad segments of MS market show how wide the market is and the many opportunities it has brought forth. The first distinction between single and triple quad is that the nature of sensitivity. The triple quad are more improved than single quad and therefore they have higher sensitivity in addition it has higher resolution. Triple quad provides data on both the mass and the sample structure unlike the single quad. The triple quad is more popular nowadays due to its improved features.
Reference
Bahrke, M.S., Yesalis, C.E., Performance enhancing substance in sport and exercise; Eds.; Human kinetics: Champaign, II, 2002; pp33-46
Zaia J. Biemann K. Comparison of charged derivatives for high energy collisions induced dissociation tandem mass spectrometry. Journal of the American Society for mass spectrometry 6, 428-436
