4. How to mount the emitters
Select an appropriate union to connect your analytical column to the bare capillary emitter. Common union/fitting options: Valco 360 metal union, Valco reducing union, IDEX plastic union.
1. Background:
Electrospray Ionization (ESI) gently converts molecules in solution into gas-phase ions using a high-voltage spray. This process generates multiply charged ions, making it ideal for analyzing large or fragile molecules.
ESI is widely used in proteomics, metabolomics, and pharmaceutical analysis. Its performance relies on the emitter forming a stable Taylor cone and consistent spray for efficient, reproducible ionization.
Emitters can face clogging, poor wetting, or unstable spray. These issues can reduce sensitivity and lead to intermittent signals.
2. MicrOmics' History with Emitters:
MicrOmics pioneered advanced ESI emitter technology. In 2005, Dr. Ryan Kelly introduced the original Stinger Constant-ID Etched-Tip (CET) emitter at PNNL to address instability and clogging.
In 2024, MicrOmics launched Pulled-Etched-Tip (PET) emitters with narrower openings, expanding their application across LC-MS platforms.
3. CET and PET Comparison:
Constant id. Etched-Tip ESI Emitter (CET)
- No clog-prone internal taper, providing uninterrupted operation
- Thousands of LC–MS analyses performed with a single emitter
- Taper-free chemically etched emitters last up to 4× longer than pulled silica emitters¹
- Fabricated using a proprietary chemical etching process with a near-zero-degree end taper¹, ensuring outstanding spray stability and robustness
Pulled- Etched-Tip ESI Emitter (PET)
- Flexible opening options with various inner diameter sizes
- More rigid structure achieved through pulling process
Shared Features:
Sharper tip, less than 4 degree angle, lower voltage required down to maintain stable spray
Ultra-smooth surface achieved through chemical etching for a uniform, clean finish
Low back pressure with minimal additional resistance despite smaller orifice size
Superior spray stability due to thin-wall design, preventing wetting and enabling ultra-stable sprays
Polished inlet ensuring optimal connection and sealing, minimizing dead volume
Learn more about Emitter Technologies:
Note that for the PEEK union voltage must be applied at the column inlet.
After connecting the column and emitter, place the union in the cradle of the Flex source arm and secure it in position. If applying voltage at this junction, you may need to connect the voltage applicator before or after securing the union, depending on your setup.
And other adapters, e.g., ESI adapter, and other emitter adapters.
5. Constant i.d. Etched-Tip (CET) Details
Detailed Features
A. Why small ID and low flow rate ESI?
Using a small ID (inner diameter) emitter and a slow flow rate can significantly improve the efficiency of Electrospray Ionization (ESI) in mass spectrometry.
Small ID Emitter: (1) Higher Electric Field Strength, (2) Smaller Droplet Size (3) Reduced Coulombic Explosions (more stable spray) Slow Flow Rate: (1) Better Desolvation (2) Reduced Ion Suppression (3) Improved Ionization Efficiency and (4) Enhanced Stability.
Overall, a small ID emitter is used in conjunction with a slow flow rate would lead to
Higher Sensitivity: The combination of smaller droplets and better desolvation results in higher ionization efficiency, leading to increased sensitivity for detecting analytes. Improved Resolution: The stability of the electrospray and the reduced ion suppression effects contribute to better resolution and more accurate mass measurements.
Lower Detection Limits: The enhanced ionization efficiency and reduced background noise allow for the detection of analytes at lower concentrations.
In the following graph, we can see lowering the spraying flow rate from 300 nL/min to 20 nL/min lead to over 10 x more signal per analyte molecule.
B. Stable spray flow across wider range of flow rate (10-µm-i.d. emitter showing here)
C. Unprecedented flow stability across a wide range of flow rates. Scans below were obtained using a 10-µm-i.d. emitter.
D. Proven result with stable sensitivity down to single cell level.
Truong, T.; Webber, K. G. I.; Madisyn Johnston, S.; Boekweg, H.; Lindgren, C. M.; Liang, Y.; Nydegger, A.; Xie, X.; Tsang, T.-M.; Jayatunge, D. A. D. N.; et al. Data-Dependent Acquisition with Precursor Coisolation Improves Proteome Coverage and Measurement Throughput for Label-Free Single-Cell Proteomics. Angew. Chem. Int. Ed. 2023, 62 (34), e202303415. DOI: https://doi.org/10.1002/anie.202303415.
6. Pulled-Etched-Tip (PET)
Our PET emitters combined the advantage of traditionally pulled emitter with our unique etch method to give you the flexibility on orifice size.
7. Common Dimensions and Customization available (Thermo, Bruker, Waters and SCIEX)
| MS System (Vendor) | Emitter Configuration |
|---|---|
| Thermo MS | 20 µm ID, 360 µm od, 5 cm long |
| Waters MS | 20 µm ID, 360 µm od, 6.25 cm long |
| Brukers MS | 20 µm ID, 360 µm od, 2 cm long |
| SCIEX MS | 20 µm ID, 360 µm od, 7 cm long |
Other configurations available:
- Inner diameters: 5 - 250 µm
- Lengths: as short as 2cm, as long as 100 cm
8. Related Products
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Standard - Pulled-Etched-Tip (PET) ESI Emitters - 20µm x 50mm (5pk, EMPA)
Regular price $300.00Sale price $300.00Unit price per -
Other - Constant i.d. Etched-Tip (CET) ESI Emitters - 5pk
Regular price $300.00Sale price $300.00Unit price per -
Other - Pulled-Etched-Tip (PET) ESI Emitters - 5pk
Regular price $300.00Sale price $300.00Unit price per
9. FAQ (frequently asked questions)
Our most popular emitter is Constant i.d. Etched-Tip (CET) ESI Emitters - 20µm x 50mm (5pk, EMCA), our users choose this to maximum the robustness while still get excellent spray stability.
Absolutely, we do custom emitter for both etched and pulled emitter, different ID, opening as well as end fitting, just shoot us an email at info@micromicstech.com, we will provide the best we can for you.
No worry, MicrOmics is a scientists own and run company, we understand the frustration of getting something that not work as good as it should. We will try our best to satisfy your need, if not we offer 30 days money back guarantee, see our satisfaction guarantee here.
10. Related Documents
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11. Testimonials and References
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“We are truly impressed by the performance of MicrOmics products. MicrOmics emitters outperformed the ones we had relied on for nearly 20 years—lasting longer and delivering far greater stability.” Yanbao YuDirector of Proteomics, University of Delaware, PA, USA -
Reference: Ribosome-inactivation by a class of widely distributed C-tail anchored membrane proteins https://doi.org/10.1016/j.str.2024.09.019 Njenga et. al. -
High-quality, lightweight, and thoughtfully designed Author name -
Reference: Recombinant production of spider silk protein in Physcomitrella photobioreactors https://doi.org/10.1007/s00299-025-03485-y Ramezaniaghdam et. al. -
Reference: Multicolumn nanoflow liquid chromatography with Accelerated offline gradient generation for robust and sensitive single-cell proteome profiling https://doi.org/10.1021/acs.analchem.4c00878 Xie et. al. -
Reference: Data‐dependent acquisition with precursor coisolation improves proteome coverage and measurement throughput for label‐free single‐cell proteomics Truong, etc.
