Evaluation of a commercial electro-kinetically pumped sheath-flow nanospray interface coupled to an automated capillary zone electrophoresis system

Abstract

Capillary zone electrophoresis-electrospray ionization-mass spectrometry (CZE-ESI-MS) is attracting renewed attention for proteomic and metabolomic analysis. An important reason for this interest is the maturation and commercialization of interfaces for coupling CZE with ESI-MS. One of these interfaces is an electrokinetically pumped sheath flow nanospray interface developed by the Dovichi group, in which a very low sheath flow is generated based on electroosmosis within a glass emitter. CMP Scientific has commercialized this interface as the EMASS-II ion source. In this work, we compare the performance of the EMASS-II ion source with our in-house system. The performance of the systems is equivalent. We also couple the EMASS-II ion source with a PrinCE Next|480 capillary electrophoresis autosampler and an Orbitrap mass spectrometer, and analyzed these system’s performance with in terms of sensitivity, reproducibility, and separation performance for separation of tryptic digests, intact proteins, and amino acids. The system produced reproducible analysis of BSA digest; the RSDs of peptide intensity and migration time across 24 runs were less than 20% and 6%, respectively. The system produced linear calibration curve of intensity across a 30-fold range of tryptic digest concentration. The combination of a commercial autosampler and electrospray interface efficiently separated amino acids, peptides, and intact proteins, and only required 5 μL of sample for analysis.

On‐line capillary electrophoresis/laser‐induced fluorescence/mass spectrometry analysis of glycans labeled with Teal™ fluorescent dye using an electrokinetic sheath liquid pump‐based nanospray ion source

“…Although high reactivity and separation efficiency of the Teal™ dye in CE/LIF assays have been reported earlier, MS detection of Teal‐labeled glycans is highly desirable to generate accurate identification and minimize peak assignment ambiguity. The CE/MS method that we adopted for the analysis of Teal‐labeled glycans uses an electrokinetically pumped nanospray sheath liquid CE/MS interface design (Figure S1, supporting information) . The analytes are injected into the separation capillary from the capillary inlet, which is placed inside the CE system.…”

“…However, soon it was realized that the BGE of 0.7 M ammonia, 0.1 M ɛ‐aminocaprioic acid, 70% methanol as previously reported generated very high mass spectrometry background, preventing effective glycan identification. Taking into consideration that the previously reported CE/MS work was carried out using a much higher sheath liquid flow than that on the EMASS‐II ion source, it was decided to remove ɛ‐aminocaprioic acid from the formulation, and only use ammonium hydroxide and methanol in the BGE buffer. Figure shows the CE/MS result of a mixture of Teal‐A2F and unlabeled A2F using 0.5 M ammonium hydroxide, 50% methanol.…”

“…The CE/ MS method that we adopted for the analysis of Teal-labeled glycans uses an electrokinetically pumped nanospray sheath liquid CE/MS interface design (Figure S1, supporting information). [16][17][18][21][22][23] The analytes are injected into the separation capillary from the capillary inlet, which is placed inside the CE system. The capillary outlet was, instead of being placed inside the CE unit, taken out and placed through a CE/MS interface tee, pointing towards the mass spectrometer.…”

Recent developments and applications of capillary and microchip electrophoresis in proteomics and peptidomics (2015–mid 2018)

“…The latter can be divided into coaxial sheath flow and liquid junction interfaces. Even though some commercial interfaces for coupling CZE with ESI-MS [82][83][84] are available, many interfaces employed in CE-MS applications are laboratory-built [85][86][87][88][89]. While ESI interfaces are usually coupled on-line, MALDI interfaces are generally combined in off-line mode.…”

Recent advances in protein analysis by capillary and microchip electrophoresis

“…The same group performed CZE-ESI-MS in a LPA-coated capillary for proteomics and intact protein analysis. 83 In this work, the authors compared the performance of a commercial electrokinetically pumped sheath flow nanospray interface (EMASS II) with their homemade instrument. 81, 82 The two systems produced nearly identical numbers of protein and peptide identifications: 399 protein identifications/1372 peptide identifications vs 388 protein identifications/1258 peptide identifications.…”