A chemometric study of active parameters and their interaction effects in a nebulized sheath-liquid electrospray interface for capillary electrophoresis - mass spectrometry

• A chemometrics approach has been used for evaluating the effect of four experimental parameters when coupling capillary electrophoresis (CE) to electrospray ionization-mass spectrometry (ESI-MS). Electrospray voltage, sheath-liquid flow rate, nebulizing gas flow rate, and spray needle position in respect to the MS orifice were varied according to a full factorial design. In addition to main effects, two interaction effects could be identified as significant when measuring the peak intensity of the analytes, from a sample mixture containing peptides and pharmaceuticals. The first interaction effects, between the nebulizing gas flow rate and the sheath-liquid flow rate, and the second interaction effect, between the nebulizing gas flow rate and the spray poisition, could further explain the impact that these variables have on the spray performance. The number of theoretical plates and the baseline noise were also measured. The sheath-liquid flow was found to significantly affect the separation efficiency, while the noise level mainly was controlled by the nebulizing gas flow. The same factorial design was also used for a CE capillary with lower internal diameter (ID) and the effects of the same variables were compared on those capillaries using equal injection volume for both capillaries. Similar trends were obtained in both capillaries but capillary ID was shown to be a significant variable when evaluating both capillaries in a single model. It was found that a capillary with 25 um ID provided improved CE-MS performance over than corresponding 50 um ID capillary. Enhanced sensitivity was obtained using the narrow-bore capillary, and at lower sheath-liquid flow rat the 25 um ID capillary also gave rise to more efficient peaks.

Nyckelord

Capillary electrophoresis

Chemometrics

Electrospray

Interaction effects

Mass spectrometry

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