1 Introduction 4 Schlieren Study 5 Modified Source 6 TLC Plate … · Presented here is a DAPCI...
Transcript of 1 Introduction 4 Schlieren Study 5 Modified Source 6 TLC Plate … · Presented here is a DAPCI...
A Modified Direct Sample Analysis (DSA) Ionization Source for the Direct Analysis of Thin-Layer Chromatography (TLC) Plates
Gregory T. Winter; Joshua A. Wilhide; William R. LaCourse
Molecular Characterization and Analysis Complex, University of Maryland, Baltimore County, Baltimore, MD 21250
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2 Previous Strategies
Introduction 5
Conclusion
Figure 1. A) Schematic of the DSA ionization source. B) Overall view of the DSA
attached to the AxION TOF. C) Close up view of the DSA with covers off
D) Close up view of the DSA sample tray inlet to the AxION TOF.
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Mesh Sample Tray
Nebulization Gas Inlet
Liquid Inlet
Auxiliary Gas Inlet
Corona Needle
Capillary
Extender
Heater
N2(g)
N2(g)
N2(g)
Commercial Setup A
D
C B
Figure 4. A) Modified source B) Nozzle adapter front view C) Nozzle adapter side view D) Adapted glass
nozzle E) Capillary extender side view F) Capillary extender front view G) Capillary extender, nozzle and
TLC plate on sample carrier H) Capillary extender, nozzle, TLC plate, camera I) Instrument schematic J)
Camera view and computer software control
Modified Source
Figure 6. A) TLC plate under white light 1) Victoria Blue dye from a blue Sharpie 2) Caffeine ( spot not
visible under white light) 3) Acetaminophen 4) Salicalymide B) TLC plate under UV (254nm) light C)
Extracted ion chromatogram of analyzed TLC plate. D) Mass spectra of each compound from the TLC plate
Presented here is a DAPCI source for the direct analysis of TLC plates and other surfaces. The
source was modified from a commercial DSA (Direct Sample Analysis) source made by
PerkinElmer. Modifications were made to the heater and nozzle assemblies as well as the capillary
extension. While only one application is shown, this source configuration has far reaching utility.
While TLC plates offer rapid analyte separation, detection can often be time consuming and
non-specific. Strategies include retention factor comparison with a standard, specific reagent
binding or spectroscopy. Additionally, spots of interest can be scraped off the plate and dissolved in
a solvent for separate analysis. Ambient mass spectrometry has the potential to improve the analysis
of TLC plates by offering direct sampling strategies. The goal of this project was to create an
automated system to analyze TLC plates using a modified DSA source.
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E x t r a c t e d I o n C h r o m a t o g r a mP a i n B u s te r T a b l e t w i t h V i c t o r i a B l u e M a rk e rs
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Figure 2. A) Schlieren experimental setup
B) Nozzle internal diameter 1) 4.8 mm 2) 3.2 mm 3) 1.5 mm 4) 0.5 mm
TLC Plate Analysis B
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Mirror
Nozzle
Heater
Nebulizer Gas Inlet
Solvent/Reagent
Inlet
Auxiliary Gas Inlet
Corona Needle
Solvent/Reagent
Probe
Razor
Blade
MS Inlet
A
Figure 3. Schlieren photographs and corresponding water cluster mass spectra produced by
each nozzle. A) Nozzle 1 B) Nozzle 2 C) Nozzle 3 D) Nozzle 4
Decreasing nozzle internal diameter produced higher intensity water clusters.
Despite this trend the intensity decreased with the smallest nozzle. This decrease is
attributed to gas leaks within the system (circled in red above).
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Mass spectrometry has been applied previously to the analysis of TLC plates. The
techniques are divided into two categories, direct and indirect. Indirect techniques involve the
removal of the spot in question for separate analysis. Ambient mass spectrometry falls into the
direct category where the plate remains intact.
Indirect Direct
MALDI MALDI
FAB AP-MALDI
ESI-MS LD-APCI
APCI-MS LIAD-ESI-MS
GC-MS DESI
LC-MS DART
A B
C D
E F
G H
Capillary Extender
Mass Spectrometer Inlet Capillary
Nitrogen Gas Inlet
TLC Plate
X
Motor Y
Motor
High Voltage
Line
Corona Pin
I J
Figure 5. Complete assembly
The initial desire to better understand the DSA led to a study using schlieren
photography. This study illustrated how nozzle size can affect reagent ion spectra and gas
flow patterns. The knowledge gained from the study assisted us in constructing a
multidimensional platform for the analysis of TLC plates.
The new prototype platform successfully combines an automated sample stage with the
modified source. TLC plates as well as other samples have successfully been studied using
this configuration. The improvements to the heater and nozzle assembly reduce the amount
of gas leaks and improves gas flow. The smaller nozzle provides more precise sampling
over the stock design.
To fully utilize the potential of this system additional developments are required.
These developments include:
• More efficient heat transfer to the nitrogen gas
• Improve the gas flow path to further reduce leaks
• Develop more compact design
• Develop computer program to integrate all aspects of the software controls
• Improve capillary extension design to better capture desorbed ions
• New more rugged heater assembly
• Heater provides more gastight fit
• Smaller nozzle
• Improved spatial resolution
• Made of glass to prevent
electrical arching
• Automated sample xy stage
• Manual vertical source adjustment
• Camera to monitor sample position
• 254/365nm UV lamp
• External high voltage and nitrogen
control
• Longer capillary extension
Modifications made to Commercial Source
Patent Pending
2014-015WL
Schlieren Study