Off‐line integration of CE and MALDI‐MS using a closed–open–closed microchannel system

Abstract

In this work, a new technique for off-line hyphenation between CE and MALDI-MS is presented. Two closed fused-silica capillaries were connected via a silicon chip comprising an open microcanal. The EOF in the system was evaluated using mesityloxide or leucine-enkephalin as a sample and with a running buffer that rendered the analyte neutrally charged. Comparison was made between the EOF in a closed system (first capillary solely included in the electrical circuit) and in a closed-open system (first capillary and microcanal included in the electrical circuit). It was concluded that the experimental values of the EOF agreed with the theory. The influence of the capillary outer diameter on the peak dispersion was investigated using a closed-open-closed system (first capillary, microcanal and second capillary included in the electrical circuit). It was clearly seen that a capillary with 375 microm od induced considerably higher peak dispersion than a 150 microm od capillary, due to a larger liquid dead volume in the connection between the first capillary outlet and the microcanal. Mass spectrometric analysis has also been performed following CE separation runs in a closed-open-closed system with cytochrome c and lysozyme as model proteins. It was demonstrated that a signal distribution profile of the separated analytes could be recorded over a 30 mm long microcanal.

DNA methyltransferase expression in the mouse germ line during periods of de novo methylation

“…Capillary electrophoresis can readily be coupled off‐line with MALDI‐MS (for reviews see Kolch et al, 2005; Stutz, 2005; Huck et al, 2006; Mischak et al, 2009), since the nanoliter sample amounts handled in CE are inherently compatible with the microscale sample preparation characteristic of MALDI‐MS. Separation channels can even be incorporated into MALDI target plates; for example, Jacksén et al (2007) used an open microchannel on a silicon chip to separate polypeptides and proteins by CE, followed by evaporation of the CE buffer, matrix deposition, and MALDI‐MS analysis at different positions along the channel. A similar on‐plate separation method was presented by Liu et al (2001) with the exception that the MALDI matrix was directly mixed with the CE separation buffer.…”

Lab‐on‐a‐plate: Extending the functionality of MALDI‐MS and LDI‐MS targets

“…Separation channels can even be incorporated into MALDI target plates; for example, Jacksén et al (2007) used an open microchannel on a silicon chip to separate polypeptides and proteins by CE, followed by evaporation of the CE buffer, matrix deposition, and MALDI-MS analysis at different positions along the channel. A similar on-plate separation method was presented by Liu et al (2001) with the exception that the MALDI matrix was directly mixed with the CE separation buffer.…”

Peptide mapping using capillary electrophoresis offline coupled to matrix‐assisted laser desorption ionization time of flight mass spectrometry

“…Alternative detection modes include electrochemical [22], amperometric [23], potentiometric [24], conductometric [25][26][27], and laser-induced fluorescence [28,29] detection. The hyphenation of CZE to mass spectrometric techniques such as matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) allows, in addition to identification, the elucidation of the chemical structure of the separated analytes [30][31][32][33][34][35][36].…”