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GC-APCI/IMS-QTOF for the Analysis of Diesel
Sheher Bano MohsinDavid WongRob Ley
Why EPA Regulates Diesel Fuel
The amount of sulfur in diesel fuel is directly linked to the amount of pollution produced when the fuel is burned in an engine. Higher levels of sulfur increase pollutants.
Practical Advances in Petroleum
Processing, Volume 1
edited by Chang Samuel Hsu, Paul Robinson
• Instrumentation – IM-QTOF with GC1. Instrument Overview
2. Benefits of IM
• Results
Things to Cover
•Increases MS flexibility by enabling both GC and LC MS
•Analysis of wider range of compounds
•Proven QTOF LC/MS platform
•Proven 7890 GC performance
G3212A- GC APCI Interface
Page 5
0
IM-QTOF Instrument Overview
6
• System sensitivity optimized using electrodynamic ion funnels to focus and transmit ions
• Ion Mobility resolution optimized while maintaining QTOF performance (mass resolution and accuracy)
• Ion Fragmentation can be selected using standard QTOF collision cell (CID)
• Bandwidth of QTOF data acquisition and processing channel was increased by 10 fold to match the ion mobility data rates
Ion Mobility System Design
7
Ionization source: Ion generation (ESI, AJS, Nano ESI, ChipCube, GC-APCI etc.)
Front ion funnel: Efficient ion collection, desolvation and excess gas removal
Trap funnel: Ion accumulation and introducing ion packets into drift cell
Drift cell: Uniform low field ion mobility allows direct determination of accurate CCS (Ω)
Rear funnel: Efficient ion refocusing and introduction into mass analyzer
Benefits of Adding Ion Mobility to GC/Q-TOF/MS
• Adds Additional Separation Power • A new dimension of separation for increased mass spectral
purity especially for complex mixture analysis
• Improves Detection Limits • Helps to eliminate interference from other analytes and
background in the sample mixture
• Efficient ion focusing and transfer through the ion optics maximizes sensitivity for the overall system
• Enhances Compound Identification
• Improves confidence in compound identification and ion
structure correlation through accurate collision cross section
measurements
8
Excellent in Resolution and Separation Power
9
Chromatography Ion Mobility Mass
~ minutes ~ 60 milli-seconds ~ 100 m seconds
IMS fits between LC and TOF MS on the separation time scale
Adding Ion Mobility Spectrometry
An Additional Dimension of Full Spectral Specificity
Mass Spectrum
Signal Response
Agilent Restricted Page 10
Chromatogram ~ minutes
Drift Spectrum ~ 60 msec
Mass Spectra ~ 100-200 usec
tdrift
Detector
AnalyteIons
GatingOptics
Ion Mobility Cell
t0
VH VL
Electric Field
Stacked ring ion guide gives linear field
Basic Operational Principle of Ion MobilityFor Conventional DC Uniform Field IMS
June 27, 2016 11
𝑣 = 𝐾 𝐸 ∝𝑒 𝐸
𝑃 𝑇 Ω
Resolving Structural Sugar Isomers C18H32O16
June 27, 2016 12
Melezitose
Raffinose
Resolving two isobaric trisaccharides
Conformational Space Occupancy of Biomolecules
Co
llis
ion
Cro
ss S
ecti
on
(Å2)
Mass (Da)
Hypothetical Ordering ofBiomolecular Classes
lipids
carbohydrates
peptides
oligonucleotides
Lipid Analysis
Tetraalkylammonium Salts+2 ions
+3 ions
+1 ions
+4 ions
Ion
Mo
bilit
y D
rift
Tim
e (
ms)
Mass (Da)
0
0
20
40
50
500 1000 1500 2000
10
30
60
70
L-α-phosphotidylethanolamines (PE)
TAA-3
TAA-16
TAA-12
TAA-10
TAA-8TAA-7
TAA-6TAA-5
TAA-4
GC-APCI-IMS of Diesel
C12H8S
C14H12SC13H10S
C15H14S
C16H14S
Extracting the dibenzothiophenes(Mass defect below 0.1 amu)
Diesel B
Diesel C
Kendrick Mass Defect Plot showing series of related compounds with
same Kendrick mass Defect
184 198 212 226 240 254
Dibenzothiophenes in Diesel Sample before HDS
Comparing Diesel B to C
Comparing elution profile in the same retention time window for the treated and untreated samples
Chromatogram of Diesel sample before HDS
Focusing on one area of the map
Kendrick Plot showing Background and 4,6-DBT with their respective different mass defects
Species separated out by different drift times
Sulfur and Desulfurized Compounds
C13H10S
Ring Structures with Sulfur
Drift Spectra
Drift Spectra of a series
C9H8S
Complexity around 149 m/z
Deisel Sample after HDS
Focusing on a small area
Kendrick Mass Defect for a series of related Compounds with KMD of 0.1008
C12H8, C13H10, C14H12, C15H14, C16H16, C17H18 etc
C15H18
C15H16
C15H20C15H22
IMS map for molecular weights from m/z 178 - m/z 232
Addition of methyl group within a C15 series
C15H18C15H20
C15H22
C15H16
C15H14
C15H12
Extracting a thin slice of the chromatogram
Several Possible Structures
4.4 minutes
3.4 minutes
• IM-QTOF with the GC-APCI interface can be used to study HDS
Conclusions• IM-QTOF with the GC-APCI interface can be used to study HDS
Acknowledgements
• Ken Imatani
• David Wong
• Rob Ley