Скачать презентацию This HP GC MSD is comprised of a HP Скачать презентацию This HP GC MSD is comprised of a HP

9d19e98357879e965fb255a4d31d4976.ppt

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This HP GC/MSD is comprised of a HP 6890 GC interfaced to a HP This HP GC/MSD is comprised of a HP 6890 GC interfaced to a HP 5972 Mass Selective Detector Quadrupole Mass Spectrometer. The system uses electron impact (EI) ionization and is capable of performing full mass scans or selective ion monitoring (SIM).

REVERSED PHASE HPLC REVERSED PHASE HPLC

Gas Chromatography –The sample mixture is injected and vaporized. Next the mixture is transported Gas Chromatography –The sample mixture is injected and vaporized. Next the mixture is transported through the heated column by the flow of an inert, gaseous mobile phase. The column contains a thin coating of a liquid stationary phase which differentially retards the migration of the sample components. (Separated Components)

A. 25 mm ID column is commonly use for arson analysis (Liquid stationary phase. A. 25 mm ID column is commonly use for arson analysis (Liquid stationary phase. 25 um thickness) < Air Chromatogram

DYNAMIC PARTITIONING TAKES PLACE IN GAS (LIQUID) CHROMATOGRAPHY DYNAMIC PARTITIONING THE ANALYTES PARTITION BETWEEN DYNAMIC PARTITIONING TAKES PLACE IN GAS (LIQUID) CHROMATOGRAPHY DYNAMIC PARTITIONING THE ANALYTES PARTITION BETWEEN THE STATIONARY LIQUID PHASE AND THE MOBILE GAS PHASE.

N= # of theoretical plates N= # of theoretical plates

(Used for packed columns) Carrier Gases NITROGEN, HELIUM AND HYDROGEN HAVE DIFFERENT SLOPES (Used for packed columns) Carrier Gases NITROGEN, HELIUM AND HYDROGEN HAVE DIFFERENT SLOPES

“SELECTIVITY” IS DETERMINED BY THE STATIONARY PHASE CHEMISTRY (K’) IS OPTIMIZED BY TEMPERATURE PROGRAMMING “SELECTIVITY” IS DETERMINED BY THE STATIONARY PHASE CHEMISTRY (K’) IS OPTIMIZED BY TEMPERATURE PROGRAMMING

In order for the reaction (fire) to happen, there needs to be an ignition In order for the reaction (fire) to happen, there needs to be an ignition source (a spark or friction), oxygen (air) and a fuel source (such as ignitable liquids).

Normal Alkane Cycloalkane Branched Alkane (Isoparaffin) Thermo-Decomposition Normal Alkane Cycloalkane Branched Alkane (Isoparaffin) Thermo-Decomposition

THERMODECOMPOSITION IGNITABLE LIQUID MIXTURE THERMODECOMPOSITION IGNITABLE LIQUID MIXTURE

The retention (retention time) of a compound depends not only on the column length, The retention (retention time) of a compound depends not only on the column length, the type of stationary phase and flow rate, but also on the column temperature. As the temperature increases, compounds move through the column faster. Thus, one can reduce the analysis time by increasing (temperature programming) the column temperature. In this run the column temperature is increased from 40 C to 240 C at 10 C/ min during the analysis. All of the normal alkane components are completely separated into narrow symmetrical peaks. t

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Pattern recognition Pattern recognition

Peak (component) Co-elution Peak (component) Co-elution

In addition to a profile of the separated components (chromatogram), the mass spectrometer produces In addition to a profile of the separated components (chromatogram), the mass spectrometer produces a mass fragmentation pattern (mass spectrum) for each separated component (compound). < Mass Spectra

Control Panel Column Oven Ion Trap Control Panel Column Oven Ion Trap

Showing the different electrical potentials applied to the ion trap With additional wave form Showing the different electrical potentials applied to the ion trap With additional wave form manipulations applied to the End-cap electrodes, MS/MS can be used to further analyze fire debris containing matrices.

Special Note! Special Note!

(Ion Trap and Quadrupole Mass Filter) (Ion trap) (Ion Trap and Quadrupole Mass Filter) (Ion trap)

a q || qz a q q q m a q || qz a q q q m

The ions are scanned (stabilized) from the lowest mass to the highest mass (with The ions are scanned (stabilized) from the lowest mass to the highest mass (with unit resolution) through the quadrupole filter and detected by the detector.

DC and RF voltages (+) Rods (-) Rods DC and RF voltages (+) Rods (-) Rods

RF >DC RF >DC

^ ^

Ethylbenzene Ethylbenzene

Note the ions 43, 57 and 71 Normal Alkane Heptane n-C 7 Note the ions 43, 57 and 71 Normal Alkane Heptane n-C 7

Note the ions 39, 55, 67(& 69) and 83 Methylcyclohexane Cycloalkane Note the ions 39, 55, 67(& 69) and 83 Methylcyclohexane Cycloalkane

Note the ions 43, 57, 71 and 85 Normal Alkane Octane (n-C 8) Note the ions 43, 57, 71 and 85 Normal Alkane Octane (n-C 8)

Note the ions 39, 55, 67 and 83 Cycloalkane Ethylcyclohexane Note the ions 39, 55, 67 and 83 Cycloalkane Ethylcyclohexane

Alkene Polystyrene and Polypropylene Decomposition Alkene Polystyrene and Polypropylene Decomposition

Ion summed extracted ion profiling is also routinely used. But to illustrate how to Ion summed extracted ion profiling is also routinely used. But to illustrate how to differentiate between branched alkanes (Isoparaffins) and normal alkanes, the following slides are highlighted.

No Apparent Equally Spaced Intense Peaks No Apparent Equally Spaced Intense Peaks

Unknown Mixture Based on the position of the unknown mixture to the reference peak Unknown Mixture Based on the position of the unknown mixture to the reference peak (1, 2, 4 Trimethylbenzene) found in gasoline, the mixture is a medium range product.

Ion averaging of all the ions in the TIC Virtually no aromatic ions (91, Ion averaging of all the ions in the TIC Virtually no aromatic ions (91, 105, 119, 134) Unknown Mixture No dominant cycloalkane ions (55, 69, 83, 97) Not a Naphthenic Paraffinic Product (Isoparaffin Product? ) (Normal Alkanes? ? ) Note Ratio < Ratio of ion 57 to ion 43 is found in isoparaffins

Retention Time of 7. 97 min Unknown Mixture Note Ratio Has the ion ratio Retention Time of 7. 97 min Unknown Mixture Note Ratio Has the ion ratio of a branched alkane (isoparaffin) and has a molecular ion of 156 Daltons

Mass Spectrum Of Peak From the Unknown Mixture (Retention Time of 7. 97 min) Mass Spectrum Of Peak From the Unknown Mixture (Retention Time of 7. 97 min) Appears to be an Isoparaffin ! Library Search Results Of The Above Mass Spectrum Branched Alkane (Isoparaffin) (molecular ion of 156 Daltons)

Mixture contains n-C 11 Comparison of the unknown mixture in the previous slides to Mixture contains n-C 11 Comparison of the unknown mixture in the previous slides to a mixture containing n-alkanes Retention Time 10. 334 min The normal alkane n-C 11 (Undecane) has a molecular ion of 156 Daltons

Reference Reference

In summary, the unknown is a Medium Isoparaffinic Product. In summary, the unknown is a Medium Isoparaffinic Product.

Library Search Results Library Search Results

Weathered Gasoline Weathered Gasoline

In the following ignitable liquid classifications, the various ignitable liquids are compared to gasoline. In the following ignitable liquid classifications, the various ignitable liquids are compared to gasoline. 1, 2, 4 -Trimethylbenzene found in gasoline is the reference peak. 1, 2, 4 -TRIMETHYLBENZENE co-elutes or has a retention time similar to decane (n. C 10). A solvent or solvent mixture that is to the left of the reference peak is considered a light product or light mixture. A narrow range mixture that is centered relative to the reference peak (or is just to the right of) is a medium mixture. Any wide range mixture, whose center of peaks is to the right of the reference peak, is a heavy mixture. Light Petroleum Distillate Classification There are many commercial solvents and solvent mixtures available to the general public. Ignitable liquid classification schemes have been developed to group (classify) the various solvents and solvent mixtures. In addition, (if a mixture is light, medium or heavy) the composition will further determine the overall classification (see the classification scheme at the end of the presentation).

A solvent or solvent mixture that is to the left of the reference peak A solvent or solvent mixture that is to the left of the reference peak is considered a light product or light mixture. A narrow range mixture that is centered relative to the reference peak (or is just to the right of) is a medium mixture. Any wide range mixture, whose center of peaks is to the right of the reference peak, is a heavy mixture. The reference peak is 1, 2, 4 -TRIMETHYLBENZENE (n-C 10 has a similar retention time or may co-elute) found in the gasoline reference.

TIC (Total Ion Chromatogram) TIC (Total Ion Chromatogram)

A solvent or solvent mixture that is to the left of the reference peak A solvent or solvent mixture that is to the left of the reference peak is considered a light product or light mixture. A narrow range mixture that is centered relative to the reference peak (or is just to the right of) is a medium mixture. Any wide range mixture, whose center of peaks is to the right of the reference peak, is a heavy mixture. The reference peak is 1, 2, 4 -TRIMETHYLBENZENE (n-C 10 has a similar retention time or may co-elute) found in the gasoline reference.

A solvent or solvent mixture that is to the left of the reference peak A solvent or solvent mixture that is to the left of the reference peak is considered a light product or light mixture. A narrow range mixture that is centered relative to the reference peak (or is just to the right of) is a medium mixture. Any wide range mixture, whose center of peaks is to the right of the reference peak, is a heavy mixture. The reference peak is 1, 2, 4 -TRIMETHYLBENZENE (n-C 10 has a similar retention time or may co-elute) found in the gasoline reference.

A solvent or solvent mixture that is to the left of the reference peak A solvent or solvent mixture that is to the left of the reference peak is considered a light product or light mixture. A narrow range mixture that is centered relative to the reference peak (or is just to the right of) is a medium mixture. Any wide range mixture, whose center of peaks is to the right of the reference peak, is a heavy mixture. The reference peak is 1, 2, 4 -TRIMETHYLBENZENE (n-C 10 has a similar retention time or may co-elute) found in the gasoline reference.

Kerosene std Heavy Naphthenic Paraffinic Product Weathered Gasoline std Kerosene std Heavy Naphthenic Paraffinic Product Weathered Gasoline std

The n-aldehydes have been found in a number of suspected arson cases. The n-aldehydes The n-aldehydes have been found in a number of suspected arson cases. The n-aldehydes can be confused for n-alkanes under the right conditions.

< Trimer Alkenes < Trimer Alkenes

Polystyrene and Polypropylene Thermo-Decomposition . Polystyrene and Polypropylene Thermo-Decomposition .

GASOLINE POLYMER CONTAMINATION GASOLINE POLYMER CONTAMINATION

UNK 1 Gasoline std Extracted Ion 119 Extracted Ion 134 UNK 1 Gasoline std Extracted Ion 119 Extracted Ion 134

A number of the above classes of ignitable liquids are encountered in fire debris A number of the above classes of ignitable liquids are encountered in fire debris analysis (testing). An in-house library of ignitable liquids from the various classes should be built with chromatograms (TIC), extracted ion profiles and mass spectra.