Gc Presentation 6a1514

GAS CHROMATOGRAPHY (GC) Mobile Phase (N2)

Separation of individual components from a sample mixture through the repeated distribution of the components between the stationary phase (column) and a gaseous mobile phase (Nitrogen). Stationary Phase (column)

AA C AC C C C AABC B B B AB B BC Sample

AA A A AA

B BB B B B

CCC C CC C

separated components

GAS CHROMATOGRAPHY-FLOW DIAGRAM Flame Gases (H2 & Air)

FlameIonization Detector (FID)

Carrier Gas (N2)

Flame

Injector (Sample Injection)

Column

Oven

Columns Used :-

NETEL GC 10%FFAD/CHROMWHP –S.S. 15%DLES/CHROMWHP –GLASS NUCON GC

S.S. Column/PORAPAK-Q ()

Specifications :-

As Per Reference

NETEL GC – MICHRO9100

CRITERIA FOR GC •

Technique of choice for separating thermally stable and volatile compounds

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Basics --

• Distribution of sample between two phases, • Stationary bed of large surface area (COLUMN) • Second is mobile phase – a gas that percolates through the stationary phase (Nitrogen)

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GLC: stationary phase is a liquid coated on a inert solid

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GSC: solid adsorbent as a stationary phase

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Versatile and selective

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Large range of liquid phases with usable temp upto 450°C

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Can be used to analyze gaseous, liquid and solid samples

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Sample MUST be volatile at temperatures BELOW 350°C

ADVANTAGES OF GC  Speed – Very fast, run can be completed in minutes

 Resolution – High resolution of closely related compounds  Qualitative analysis – Identification of substance by retention time  Quantitative analysis – Quantification of identified substance by area under peak

 Sensitivity – Highly sensitivity (can be quantified in ppm range)  Simplicity – Relatively simple to operate and understand

COLUMN TYPES • Capillary (open tubular)  Inner wall modified with thin (1 m) film of liquid  0.3 - 0.5 mm ID; 10 - 50 m length  Can load few g analyte only  WCOT, SCOT, PLOT, FSOT

• Packed  Solid particles either porous or non-porous coated with thin (1 m) film of liquid  1 - 8 mm ID; 1 - 10 m length  Can load upto few hundred g analyte

IMPORTANCE OF TEMPERATURE IN GC ANALYSIS Injection Port Temperature Hot enough to vaporize the sample rapidly Low enough to avoid thermal decomposition or rearrangement of the sample Column Temperature High enough so that analysis is accomplished in reasonable time Low enough that separation is achieved Retention time approx. doubles for every 30°C decrease in temperature Lower the temperature, higher the ratio of partitioning coefficients in stationary phase Temperature programming for effective separation Detector temperature Type of detectors – Flame-ionization detectors (FID), Thermal Conductivity Detector (TCD) etc. Hot enough to prevent condensation of sample, peak broadening and loss of component peaks TCD is more sensitive to temperature than FID

ADVANCEMENTS IN GC  Headspace GC  To detect volatile components in sample  To analyze vapours above the sample (liquid)  Multiple headspace extraction

 Gas Chromatography – Mass Spectrometry (GC-MS)  Detection of residual solvents in pharmaceutical  Study of constituents of essential oil  Determination of fatty acids

GC-MS Process

ANY QUESTIONS