Gc ms

Gas chromatography-mass spectrometry (GC MS) is an analytical method in which GC is coupled with MS to identify different substances within a test sample.

1. Gas Chromatography–Mass Spectrometry (GC-MS) Presented by Anusiya G 30-Apr-19 1

2. INTRODUCTION Gas chromatography–mass spectrometry (GC MS) is an analytical method in which GC is coupled with MS to identify different substances within a test sample. 30-Apr-19 2

3. PRINCIPLE The sample solution is injected into the GC inlet where it is vaporized and swept onto a chromatographic column by the carrier gas (usually helium ). The sample flows through the column and the compounds comprising the mixture of interest are separated by virtue of their relative interaction with the coating of the column ( stationary phase ) and the carrier gas (mobile phase ). - the stationary phase is either solid (GSC) or liquid polymer (GLC). The latter part of the column passes through a heated transfer line and ends at the entrance to ion source where compounds eluting from the column are converted to ions . The mass spectrometer identifies and quantifies the compounds according their mass-to-charge ratio (m/z) . 30-Apr-19 3

4. Sample Nature :- Samples must be volatile or semi volatile thermally stable mixtures State :- Organic compounds must be in solution for injection into the gas chromatograph. The solvent must be volatile and organic ( for example , hexane or dichloromethane ). Amount :- Depending on the ionization method, analytical sensitivities of 1 to 100 pg (0.001 to 0.1ng) per component are routine . Preparation :- Sample preparation can range from simply dissolving some of the sample in a suitable solvent. 30-Apr-19 4

5. INSTRUMENTATION 30-Apr-19 5 Figure 1 schematic diagram of GC-MS

6. In GC Gas supply - Carrier gas from the cylinder is fed to the instrument through the regulators and tubing. Generally the gases must be purified in order to ensure the gas supply pressure and high gas purity. Pneumatic controls : The gas supply is regulated to the correct pressure (or flow) and then fed to the required part of the instrument. Modern GC instruments have Electronic Pneumatic pressure controllers –older instruments may have manual pressure control via regulators. Injector - The entrance valve is connected to the chromatographic column with the help of injector. Here the liquid samples get volatilized. 30-Apr-19 6

7. Column- Capillary GC columns are helpful in analyzing the individual chemical compounds present in a sample. These columns are typically 10- 120 m long with of 0.10-0.50 mm internal diameter. Packed GC columns are 1-5 meters in length with 2 or 4mm internal diameter. Oven - Ovens present in GC are temperature programmable, which ranges from 50˚C to 400˚C and with cryogenic cooling can go as low as -25˚C. Interface : After separation in the GC system, analyte species have to be transported to the mass spectrometer to be ionised , mass filtered and detected. The interface in modern instruments is heated to prevent analyte condensation. 30-Apr-19 7

8. Mass spectrometer The separation of gas phase ions is according to their mass to charge ratio within the mass spectrometer using magnetic and/or electric fields to differentiate ions . Ion source - used to create molecular ions - the products are ionized in favor to analysis in the mass spectrometer. Mass analyzer : seperates the ions produced from ion source. Vacuum system : GC-MS requires high levels of vacuum for operating in more effective way. 30-Apr-19 8

9. Detector: The ionic beam which emerges from the mass analyzer, must be detected and transformed into a signal. The detector is an important part of the mass spectrometer that records the charge induced or the current produced when the ion hits the surface and then generates a signal. Control Electronics The necessary parameters of Mass Spectrometer can be selected and controlled from this panel. MS parameters can be controlled from a computer in modern instruments by using specially designed software 30-Apr-19 9

10. ADVANTAGES high sensitivity -excellent detection limits. Typically low ppb to high ppb. high selectivity -identification is based on two parameters not one -(retention time and mass spectrum must match standard). - selects analyte of interest with very high confidence Speed - typical analysis takes from 1/2 hour to approx. 1 hour analysis. 30-Apr-19 10

11. DISADVANTAGES higher capital cost. higher maintenance (time, expertise and money) for optimum results requires analyst knowledgeable in both chromatography and mass spectrometry. Improper condition of GC- results in mass spectrum with background noise Optimization of GC and MC based on types of chemicals involved. 30-Apr-19 11

12. APPLICATIONS Environmental monitoring and cleanup Criminal forensics Industrial application (analysis of inorganic gases and aromatic solvents, etc) Sports antidoping analysis Security Chemical warfare agent detection Food, beverage and aroma analysis Medicine 30-Apr-19 12

13. CASE STUDY In a case study of phytochemical profiling of chloroform of Caulerpa racemosa GC-MS analysis is done in order to confirm the presence of phytochemicals that were quantitatively and qualitatively analyzed. GC-MS analysis of chloroform extract of Caulerpa racemosa revealed 19 chemical compounds that are represented in the GC-MS chromatogram (Figure 2) ( Sivakumar et al., 2018). 30-Apr-19 13

14. CASE STUDY 30-Apr-19 14 Figure 2 : GC-MS chromatogram of chloroform extract of Caulerpa racemosa ( Sivakumar et al., 2018 )

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