ESI Chip

S. Zhang, C. K. Van Pelt, G. A. Schultz Rapid, fully automated nano-ESl/MS/MS analysis of excised 2D gel spots by the nanomate robot and ESI chip, in Proceedings of the 50th ASMS Conference on Mass Spectrometry and Allied Topics, Orlando, 2002, ThPB 025, 1549.pdf, available at www.advion.com. 

J. Xie, J. Shih, Q. He, C. Pang, Y.C. Tui, Y. Miuo, T.D. Lcez, An integratedLC-ESI chip with electrochemical-based gradient generation, New York IEEE. 

Chip Design Flow MS Mode Analytes Single-Channel ESI Chip Sample Treatment Separation Ref. 

PDMS chip with no tip EOF ESI-triple Q Psilocin (50 pmol) Buprenorphine (20 pmol) Multi-Channel ESI Chip Nil Nil 162... 

What are the functions of the sheath liquid and sheath gas used in an ESI chip for interfacing with a mass spectrometer (Figure 7.30) [290,808] (2 marks)... 

A microfabricated dialysis device was used to clean up the sample (i.e., protein) by removing the matrix interference in an ESI chip before carrying out MS analysis (see Figures 5.10 and 5.11). What substances from the matrix are removed [811] (2 marks)... 

Fig. 2. Advion s ESI Chip is an array of 100 independent nano electrospray nozzles etched in silicon. Image 1 the 10x10 array ESI Chip (chip dimensions=3.9x3.9 cm). Image 2 magnification of 10x10 array. Image 3 magnification on one nanoelectrospray device. Image 4 magnification on one nano electrospray nozzle. Reprinted with permission from Advion Bio-Sciences, Inc...

The development of a chip-based electrospray device from microfabricated nozzles has been reported [54], and was later commercialized [55] as the Nanoinate- - (Advion BioSciences, Ithaca, New York). There have been several reports of the applications of ESI chips for front-end analysis. The application of this technique has been reported in several different areas, which include quantitative bioanalysis [56,57], metabolite identification [58,59], and proteomics [60]. The Advion Nanomate 100 chip-based ESI-MS system has integrated the entire autosampler platform sans LC into an area the size of the ion source. 

A Silicon-based ESI Chip with Integrated Counter Electrode and its Applications Combined with Mass Spectrometry... 

The ESI Chip is fabricated from a double-side polished silicon wafer of 500 pm thickness. Double-side polished silicon wafers enable an inlet feature to be etched opposite the nozzle making the delivery of liquids to the nozzle possible... 

Figure 3.1 ESI Chip consisting of a 20 by 20 array of microfabricated nozzles etched from a silicon wafer. The inset shows scanning electron micrographs showing a nozzle with annular space and a nozzle prior to dielectric coating of the wafer. Nozzle dimensions in the inset are 10 pm i.d., 22 pm o.d. by 55 pm height.

Figure 3.2 Schematic of the fabrication sequence used to etch the silicon structure of the ESI Chip using a double-side polished silicon wafer. (A) The wafer after completion of photolithography and RIE of the silicon oxide on sides one and two. (B) The wafer after etching of the inlet structure on side two (bottom side on the figure). (C) The wafer after spinning resist on side one (top side on the figure), photolithography and development to define the through-channel structure. (D) The wafer after DRIE of the through-channel structure to the inlet structure. (E) The wafer after DRIE of the annular space to define the nozzle. (F) The wafer after removal of the resist and silicon oxide from the wafer.

Using Equation (3.1), the electric field at the tip of a 2 pm capillary is calculated to be 2.1 x 108 V m 1 with a solution voltage of 1 kV at a distance of 3 mm from a counter electrode. In the design of the ESI Chip, the distance between the solution and counter electrode voltages is a few micrometers and Equation (3.1) cannot be used to estimate the electric field. 

SIMION 6.0 was used to model the electric field of a pulled capillary, the ESI Chip and a chip without the integrated counter electrode to gain insights into the... 

Figure 3.4 Graph plotting the changes in the electric field calculated at the tip of the Taylor cone as the distance between the sprayer and counter electrode varies using Equation (3.1) and the SIMION models shown in Figures 3.3A and B. The ESI Chip model (Figure 3.3B) shows that the electric field is independent of the sprayer distance from the counter electrode.

Figure 3.6 Pipette tip aligned and sealed around the inlet to a nozzle of the ESI Chip using the NanoMate system that automates nanoelectrospray infusion. Spray voltage and backing pressure are optimized based on the solution solvent composition to obtain a stable spray. The NanoMate system loads a new sample into a new pipette tip and automatically positions it to a new nozzle. The chip is automatically moved to the optimized spray position.

Lipids analysis has benefited from nanoESI with the ESI Chip.24 27 Lipids isolated from cells using liquid-liquid extraction can be quantified and separated using MS-MS scans such as multiple precursor and neutral loss scanning to identify head groups and side chain information.26... 

Small-molecule quantification by automated infusion using the ESI Chip has been demonstrated to be able to provide comparable precision, accuracy and linear dynamic range compared to traditional LC-MS-MS.28 32 A linear dynamic range greater than five orders of magnitude was demonstrated which enabled validation of bioanalytical assays without the carryover limitations of LC-MS.32... 

Figure 3.7 First coupling of a nanoLC column to the ESI Chip using a liquid electrode to apply spray voltage to the effluent exiting a capillary positioned at the inlet to the ESI Chip. Make-up flow was optionally applied to adjust solvent composition to enhance ionization.

---