Partial-filling technique

Koezuka, K., Ozaki, H., Matsubara, N., and Terabe, S. (1997). Separation and detection of closely related peptides by micellar electrokinetic chromatography coupled with electrospray ionization mass spectrometry using the partial filling technique.. Chromatogr. B 689, 3—11. 

Amini, A., Pettersson, C., and Westerlund, D. (1997). Enantioresolution of disopyramide by capillary affinity electrokinetic chromatography with human alphal-acid glycoprotein (AGP) as chiral selector applying a partial filling technique. Electrophoresis 18, 950—957. 

Grard, S., Morin, P., Dreux, M., and Ribet, J. P. (2001). Efficient applications of capillary electrophoresis-tandem mass spectrometry to the analysis of adrenoreceptor antagonist enantiomers using a partial filling technique. /. Chromatogr. A 926, 3 — 10. 

Rudaz, S., Cherkaoui, S., Gauvrit, J. Y., Lanteri, P., and Veuthey, J. L. (2001). Experimental designs to investigate capillary electrophoresis-electrospray ionization-mass spectrometry enantioseparation with the partial-filling technique. Electrophoresis 22, 3316—3326. 

A Amini, N Merclin, S Bastami, D Westerlund. Determination of association constants between enantiomers of orciprenaline and me thy 1-/3-cyclodextrin as chiral selector by capillary zone electrophoresis using a partial filling technique. Electrophoresis 20 180-188, 1999. 

Further information regarding the composition of mixed micelles can be obtained by coupling to mass spectrometry. However, the use of surfactants in electrospray ionization will always be fraught with difficulties because contamination of the interface with nonvolatile tensides causes undesirable effects. Stable mixed micelles can be measured only by employing nonequilibrium conditions (only buffers without micellar components). Two further variants of MEKC-MS have been developed and successfully used in recent years, but these are not readily employed for the electrophoretic characterization of micelles, since either a partial filling technique or surfactants of high molecular mass have to be used (37). 

The partial-filling technique is a modification of ACE that has been shown to be very suitable for measuring binding constants. The methodology and interesting examples of application of this technique are summarized in... 

A Amini, U Paulsen-Sorman, D Westerlund. Principle and applications of the partial filling techniques in capillary electrophoresis. Chromatographia 50 497— 506, 1999. 

A Amini, D Westerlund. Evaluation of association constants between drug enantiomers and human aracid glycopotein by applying a partial-filling technique in affinity capillary electrophoresis. Anal Chem 70 1425-1430, 1998. 

Y Tanaka, S Terabe. Separation of the enantiomers of basic drugs by affinity capillary electrophoresis using a partial-filling technique and cq-acid glycoprotein as chiral selector. Chromatographia 44 119-128, 1997. 

Y Tanaka, Y Kishimoto, S Terabe. Separation of acidic enantiomers by capillary electrophoresis-mass spectrometry employing a partial filling technique. J Chromatogr A 802 83-88, 1998. 

E DeLorenzi, G Massolini, M Quaglia, C Galbusera, G Caccialanza. Evaluation of quail egg white riboflavin—binding protein as a chiral selector in capillary electrophoresis by applying a modified partial-filling technique. Electrophoresis 20 2739-2748, 1999. 

A number of CE/MS applications have been published in the field of chiral separations, mostly using cyclodextrins as chiral selectors. In some cases the partial-filling technique was used (see earlier). The importance of... 

A Amini, U Paulsen-Sorman. Enantioseparation of local anaesthetic drugs by capillary zone electrophoresis with cyclodextrins as chiral selectors using a partial-filling technique. Electrophoresis 18 1019-1025, 1997. 

J Heintz, M Hernandez, FA Gomez. Use of a partial-filling technique in affinity capillary electrophoresis for determining binding constants of ligands to receptors. J Chromatogr A 840 261-268, 1999. 

EM Javerfalk, A Amini, D Westerlund, PE Andren. Chiral separation of local anaesthetics by a capillary electrophoresis/partial-filling technique coupled online to micro-electrospray mass spectrometry. J Mass Spectrom 33 183-186, 1998. 

The loss in the detection sensitivity can be avoided by using the partial filling technique, in which only a small ping of the BGE containing the protein, or another UV-absorbing receptor, is... 

Hence, as previously mentioned, interfacing chiral CE with ESI/MS is severely hampered by the presence of nonvolatile additives, such as CD, which often leads to a significant loss of electrospray efficiency and ion source contamination. In order to circumvent these limitations, several approaches have been investigated, such as fhe combined column coupling with voltage switching and the partial-filling technique. 

In fhe first approach, Lamoree et al. chose a coupled capillary system in which fhe chiral separation occurred in the first capillary containing both chiral selectors and analytes. This technique was used to achieve CE-MS analysis with DM-P-CD for fhe stereoselective separation of ropivacaine. The latter was transferred via a PTFE union located in a plexiglass connection vial to a second capillary hyphenated to ESI-MS. A relatively complex sequence of timing events was necessary to ensure fhe complete analyte transfer and prevent the chiral selectors from entering fhe electrospray chamber [24]. On the other hand, the partial-filling technique has emerged as a simpler, straightforward and efficient valuable alternative to avoid potential interference of the chiral selector with MS detection. 

CD). The partial-filling technique (PFT) proved to be a suitable and efficient approach to avoid MS source contamination, as well as signal suppression due to nonvolatile additives. Therefore, fhe PFT technique is particularly adapted with chiral selectors added into fhe electrolyte solution. Because of fhe counter-current contribution, charged chiral selectors were found to be more suitable for the online MS detection of separated enantiomers. Capillary electrochromatography with chiral stationary phases has also been developed, but to a lesser extent. 

Alpha-1-acid glycoproteins (220,221), bovine serum albumin (222-224), pepsin, and cellobiohydrolase I (223) have been used as chiral selectors. In general, enantiomeric separation increases with increased protein concentration however, this results in a sensitivity loss due to high background signal. The use of a partial filling technique for the capillary injection to overcome this limitation has been reported (220,221). 

Molina, M., Wiedmer, S. K., Jussila, M., Silva, M., and Riekkola, M. L., Use of a partial filling technique and reversed migrating micelles in the study of A -methylcarhamate pesticides hy micellar electrokinetic chromatography-electrospray ionization mass spectrometry, J. Chromatogr. A., 927, 191, 2002. 

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