Capillary electrochromatography/mass spectrometry (CEC/MS) has so far only been performed using electrospray or microspray ionization. CEC has, to date, not been reported coupled online to nanospray ionization, due to practical difficulties in coupling the CEC column to the nanospray emitter. However this combination is ideally suited, as the flow rates for CEC (100nL/min, approximately) are directly compatible with larger orifice (10μm) nanospray emitters. A CEC unit has been designed and engineered in-house, to enable the use of short columns and high field strengths, facilitating fast electro-osmotic flow and short retention times. This device was initially coupled via a 50 μm × 37 cm C18/SCX column, and then by a C6/SCX 50 μm × 45 cm column, to microspray and nanospray interfaces, also designed and built in-house. CEC/microspray-MS and CEC/nanospray-MS were successfully evaluated on an ion-trap mass spectrometer using five corticosteriods with the addition of thiourea as a flow marker. Limits of detection (S/N = 3) were found to be 500 fg (1–2 mol) for CEC/microspray-MS and initial studies using the nanospray interface have predicted detection limits in the region of 50 fg (∼100 amol).
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Warriner et al. (1998) studied this question.