A Microfabricated Dialysis Device for Sample Cleanup in Electrospray Ionization Mass Spectrometry

Abstract

A laser microfabricated device was constructed for rapid microdialysis cleanup of biological samples for analysis by electrospray ionization mass spectrometry (ESI-MS) in both off-line and on-line modes. A microdialysis membrane was sandwiched between two chips having micromachined serpentine channels. The total volume of the sample serpentine channel used for the microdialysis was 1 microL. Efficient desalting was demonstrated for both DNA and protein samples using ESI with an ion trap mass spectrometer after microdialysis against a counter flow of ESI-compatible buffer. Signal-to-noise ratios were also greatly enhanced compared to direct infusion of the original nondialyzed samples. Importantly, the microfabricated device allowed use of sample flow rates 1 order of magnitude smaller than previous designs based on a microdialysis fiber, allowing reduced sample utilization and improved sensitivity with ESI-MS. The effectiveness of the cleanup was attributed to the size difference between the sample channel and the buffer channel and the fact that the sample is continuously refreshed by the buffer counterflow. The results indicate substantial potential for construction of highly compact and rugged devices enabling field applications of ESI-MS.

Development of new methodologies for the mass spectrometry study of bioorganic macromolecules

“…On the other hand, it must be emphasized that the LC step significantly increases analysis time and decreases throughput. As an alternative to LC purification, several laboratories have used on-line dialysis prior to mass spectral analysis (Huber & Buchmeiser, 1998;Xu et al, 1998). However, that procedure is also time-consuming.…”

A eole for the MS analysis of nucleic acids in the post-genomics age

“…Indeed, the negative charges afforded by these functional groups confer nucleic acids a strong tendency to form unwanted cation adducts that can deteriorate the attainable resolution and signal to noise ratio. Over the years, alternative strategies have been devised to replace metal cations with the more volatile ammonium [42,177], which employ ion-exchange [178], reversed-phase high-performance liquid chromatography [179], metal chelation [180,181], ethanol precipitation [177], ultrafiltration, and microdialysis [182][183][184]. Although separationbased desalting is very effective for these types of biomolecules, it may also result in the unwanted dissociation of their noncovalent assemblies, either through excessive reduction of the solution ionic strength, or through direct perturbation of binding equilibria.…”

Microfluidic technologies for MALDI‐MS in proteomics

“…In particular, the integration of microfluidic systems and MS has received substantial attention following the demonstration of the first microfluidic ESI-MS interfaces in 1997 by the groups of Karger [4], Ramsey [5], and Aebersold [6]. Extensive studies on ESI-MS interfacing for coupling microfluidics to mass spectrometry have been reported, including the use of tips fabricated in glass [4,5], bulk etched silicon [7,8], and various polymers [9][10][11][12][13][14][15][16][17], as well as the integration of silica capillary tips directly into microchannel exits [18][19][20][21][22][23][24][25][26] or through a liquid junction [16]. Overall, online ESI-MS offers a simple approach for directly interfacing microfluidic analyses with MS, while providing good sensitivity and mass accuracy, and reproducible signals for effective analyte quantitation.…”