Packed capillary column liquid chromatography coupled to mass spectrometry by a simple modification of an electrospray interface

When packed capillary columns are coupled to electrospray mass spectrometry, care must be taken to reduce the dead volumes of the detector connections. In this work, the coupling between the column and the detector was made with a 20-μm i.d. fused silica capillary which was inserted in the electrospray steel needle of the probe for pneumatically assisted electrospray. Electrical contact was made at the tip of the surrounding steel needle where the liquid was eluting to the spray. The probe was then used in pure electrospray mode by turning off the assisting nitrogen gas flow. Thus, a few simple modifications of a commercial interface for pneumatically assisted electrospray made it compatible with the low flow rates from packed capillary columns. The analysis could be performed with high separation efficiency due to the low-dead-volume detector coupling.