A simplified multidimensional approach for analysis of complex biological samples: on-line LC-CE-MS

Abstract

Information on protein expression, disease biomarkers or surrogate markers and genetic disorders can nowadays be achieved from analysis of complex biological samples by liquid separation coupled to mass spectrometric (MS) detection. This paper describes fast multidimensional separation by on-line liquid chromatography (LC) and capillary electrophoresis (CE), followed by electrospray ionization (ESI) Fourier transform ion cyclotron resonance (FTICR) MS detection. This detector provides ultrahigh resolution of the detected ions, mass accuracy at the ppm-level and high sensitivity. Most of the challenge of this system lies in the development of a new interface for the on-line coupling of LC to CE. The interface developed in poly(dimethylsiloxane) provides a RSD for injection repeatability of <3.5% and surface control for unspecific binding by deactivation with a cationic polymer, PolyE-323. We have evaluated the interface, as well as the overall system, with respect to robustness and deconvolution ability. Sequence coverage for bovine serum albumin (BSA) of 93% showed a high recovery of sample in the different transfer steps through the system. The detection limit for identification is 277 ng mL(-1) (or 280 nM) on average for peptides. In the future, we expect LC-CE-MS to be a novel strategy for elucidating the chemistry of biological matrices.

Trends in CE‐MS 2005–2006

“…Only a few publications have been found between 2005 and 2006, may be because the interface is in the most cases house made and needs expertise in the handling. Recently, Bergström et al [48] developed and evaluated an online LC-CE interface made of PDMS followed by ESI-FTICR-MS detection. This interface had the ability to transfer sufficient amount of peptides from LC to CE [48][49][50].…”

Capillary electrophoresis‐electrospray‐mass spectrometry in peptide analysis and peptidomics

“…This sequence coverage has been also explored by the direct HPLC-CE-ESI-FTICR-MS coupling [43]. In that work, authors performed the on-line LC-CE-MS coupling in a similar way as previously described by the same group [116,117].…”

“…Using the whole optimized procedure LOD down to 0.3 mM for methionine-enkephalin were achieved. The same group had previously developed a coating, based on a similar polycationic polymer that was shown to work in a shorter pH range (from 4 to 8) [43,84].…”

“…An electric field for the CE separation is achieved between the negative potential at the inlet electrode, incorporated in the CE pressure chamber, and the grounded ESI emitter. Analytes are continuously sampled into the FTICR-MS detector [43].…”

“…Concerning the analysis of peptides by CE-MS, a high variety of mass analyzers have been used, mainly single quadrupole (Q), triple quadrupole (QqQ), IT, and TOF, as well as other more expensive systems as quadrupole-TOF MS [38][39][40], Hadamard transform TOF MS [41], Fourier transform ion cyclotron resonance MS (FTICR-MS) [17,[42][43][44], etc. However, the employment of these advanced MS analyzers is not so common, obviously due to their high price and more difficult operation routine.…”