The use of sol-gel frits to minimize suction effects in capillary electrophoresis-nebulizer interfaces for plasma spectrometry

A major experimental consideration, and often a difficulty when interfacing capillary electrophoresis (CE) with plasma mass spectrometry via a pneumat ic nebulizer, is the suction effect caused by the natural aspiration of the nebulizer. This has a marked affect on the CE experiment, since it may lea d to peak overlap and, ultimately, a completely degraded separation. Placin g a sol-gel frit in the sample introduction end of the capillary in a CE sy stem, interfaced with a pneumatic nebulizer at the outlet end of the capill ary, minimizes the suction effect. A two-tube oscillating capillary nebuliz er (OCN) was used in this study because of its very low liquid flow capacit y and potential for interfacing to ICP-MS. To test the fritted capillary fo r possible application to CE-ICP-MS, standard ultraviolet (UV) absorbance d etection was used for the CE separation of metallothionein and ferritin wit h a grounded nebulizer interface at one end of the capillary. With the capi llary frit and OCN interface, reasonably true electropherograms were obtain ed when compared to the CE separation performed in the traditional mode wit hout a frit and with a buffer reservoir in place at the outlet. Also, durin g this study it was found that a make-up buffer was necessary to maintain e lectrical contact to the outlet of the fritted electrophoretic capillary wh en using the OCN.