In-line sample trap columns with diatomite for large-volume injection in CZE–IM–MS

The analysis of low-abundant compounds with capillary zone electrophoresis–drift-tube ion mobility spectrometry–mass spectrometry (CZE–DTIMS–MS) is compromised due to the low injectable sample volumes in CZE and low duty cycle in DTIMS. Fritless packed in-line trap columns, using solid-phase extraction sorbent particles, have been used to increase injection volumes in CZE, but these columns are difficult to prepare and exhibit rapidly increasing back pressures. To provide smooth and complete filling of trap columns as well as to ensure higher and sustained flow rates though the columns, blends of cation and anion exchange particles with diatomite were used. The application of diatomite blends ensured the use of trap columns for at least 100 injections, with maximum injection volumes over 10 µl, which corresponds to an enrichment factor of more than 1000 over conventional injections in CZE–MS, enabling the detection of low nM concentrations of N-glycans with CZE–IMS–MS.