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Microchip atmospheric pressure chemical ionization source for mass spectrometry
Pekka Ostman1, Seppo J Marttila, Tapio Kotiaho
1Viikki Drug Discovery Technology Center, Faculty of Pharmacy, P.O. Box 56, FIN-00014 University of Helsinki, Finland.
Analytical Chemistry
|November 13, 2004
Summary
A new microchip heated nebulizer enhances atmospheric pressure chemical ionization mass spectrometry. This novel device offers improved sensitivity and cost-efficiency for chemical analysis.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Microfluidics
Background:
- Atmospheric pressure chemical ionization (APCI) is a widely used ionization technique in mass spectrometry.
- Existing APCI sources often require high flow rates and can be bulky.
- There is a need for miniaturized and more sensitive APCI systems.
Purpose of the Study:
- To develop and characterize a novel microchip heated nebulizer for APCI mass spectrometry.
- To evaluate the performance of the microchip APCI source in terms of sensitivity, stability, and quantitative repeatability.
- To compare the performance of the microchip APCI source with a commercial macro-scale APCI source.
Main Methods:
- Fabrication of the microchip using anisotropic wet etching on silicon and sputtering of an integrated heater on glass.
- Assembly of the microchip via anodic bonding to create a two-dimensional APCI source.
- Ionization initiation using an external corona-discharge needle.
- Performance evaluation using acridine as a test analyte, measuring limit of detection (LOD) and mass flow sensitivity.
Main Results:
- The microchip APCI source operates at low flow rates (down to 50 nL/min) with stable long-term analysis (chip lifetime of weeks).
- Achieved good quantitative repeatability (RSD < 10%) and linearity (r(2) > 0.995) over 4 orders of magnitude.
- Demonstrated a limit of detection of 5 nM for acridine at 6.2 μL/min flow rate, with a mass flow sensitivity of 0.52 fmol/s.
- Outperformed commercial macro-APCI in mass flow sensitivity by a factor of ~160.
Conclusions:
- The developed microchip heated nebulizer represents a significant advancement in APCI technology.
- The microchip APCI source offers superior mass flow sensitivity and operates at significantly lower flow rates compared to conventional systems.
- This cost-efficient, miniaturized APCI source is highly attractive for various microfluidic applications and analytical detection.