EOF marker

FIGURE 2 MEEKC APPI/MS analysis of five steroids. Total ion current (TIC) and extracted ion currents (XIC) of gestrinone (GES), canrenone (CAN), metolazone (MET), finasteride (FIN), and dexamethasone (DEX) and an EOF marker (N,N-dimethylformamide, DMF). 

Figure 4 presents an example of rapid pKa measurement using a pressure-assisted system in combination with a photodiode array (PDA) detector. The migration time of DMSO (EOF marker) was measured at 220 nm, whereas the migration time of the analyte, naphazoline, was measured at 270 nm. The CE run time as well as data analysis time was drastically reduced. Consequently, this system allows the analysis of more than 96 compounds in one day. The limitation of this method is the application to drugs without UV chromophore at more than 250 nm. In some cases, it was effective to remove DMSO by evaporation under vacuum followed by the addition of methanol or acetonitrile as a neutral marker. 

In MACE, the alteration of the ionic mobility as a factor of the tenside concentration in the background electrolyte solution is a measure of the strength of interaction, which may be evaluated graphically. In Fig. 1, a schematic representation of MEKC is given for the separation of micelle and EOF markers as well as drug solutes of different lipophilicity. If the substances are neutral, their position between the EOF marker and the micelle marker is given only by their lipophilicity, which controls their affinity to the micellar phase. This means that S3 in Fig. 1 has the lowest hydrophilicity. 

Fig. 7 Mobility-shift assay for the determination of dissociation constant of the complex between anti-DNP rat monoclonal IgG21) antibody and charged ligands that contained the A-dinitrophenyl group. Mesityl oxide (MO) served as EOF marker, bovine carbonic anhydrase (CAB) and bovine a-lactalbumin (LA) as internal references. The DNP ligands with a charge of —1 (A) und —9 (B), respectively, were used as additives to the running buffer. (Reprinted with permission from Ref. 30. Copyright 1995 American Chemical Society.)...

Dual LIF and amperometric detection are used to detect a five-component mixture (see Figure 7.24). The labeled amino acids (i.e., NBD-Arg, NBD-Phe, and NBD-Glu) are fluorescently detected. The EOF marker (DA) and internal standard (CAT) are amperometric ally detected. The fluorescent peaks are normalized to the internal standard, CAT. As a result, the RSD of migration time was improved from 2.7% to 0.8% [670]. 

FIGURE 10.22 Electropherograms of the products following on-chip tryptic digestion of bovine insulin B-chain at 37°C. The flow in the reaction channel was stopped for different times to study the effect on the reaction. Control runs (see the flat curves) without insulin B-chain were performed in the continuous flow mode and in a flow with a stop time of 6 min. The arrows indicate the migration time of benzylamine, which was added as an EOF marker. All electropherograms are plotted on the same scale with an offset for clarity [1058]. Reprinted with permission from Elsevier Science. 

What neutral molecules have been used as EOF markers [670,748]. 

The mobility of an inert, neutral EOF marker through the packed segment of a CEC column has been expressed in the literature [53] by the following relationship... 

It was quickly established that thiourea was retained on all unbonded phases, and could not be used as the EOF marker. A number of other analytes was tried, and biphenyl was selected. It can be seen from Figure 3.2 that the purer silicas (Hy-PURITY and Kromasil) give a lower EOF than the more acidic traditional Hypersil... 

Figure 15 Plots of the migration time of the EOF marker against the dimensionless length of the separating column, X. The conditions were 8 cm of separating column with varying lengths of (solid) open tubular or (dash) auxiliary columns packed with silica particles, pore size 300 A applied voltage, 10 kV. Eluent, (a) 2 mM, (b) 5 mM, (c) 10 mM Na-phosphate buffer, pH 7.0, in 7 3 ACN water. (Reprinted with permission from Ref. 77, copyright 2001, Wiley.)...

CEC. The separation performed by Fujimoto et al. was achieved on a polyacrylamide gel column in 17 min [90], Phenylthiohydantoin (PTH)-labeled amino acids were separated by Horvath s group by gradient CEC on a 3-pm Zorbax C18 column and, later, by employing an immobilized packed-bed capillary [91]. Alicea-Maldonado and Colon compared the separation of three dansylated amino acids by CE and CEC using a fluoropolymer as the stationary phase [92], Elution of positively charged amino acids after the EOF marker suggested the interaction of solutes with the fluoropolymer. 

FIGURE 5.16 Effect of the ACN content on EOF mobility in CEC. Electropak phenyl column, EP-75-40-3-PH [40 cm packed (47 cm total) 75 jjim i.d.] electrolyte Tris HCl (pH 8)-ACNmixture (ionic strength 5 mM) temperature 25°C applied voltage -E20 kV UV detection 220 nm electrokinetic injection 4 s (4-10 kV) EOF marker thiourea. (Reprinted from Cahours, X., et al., J. Chromatogr. A, 845, 203-216, 1999. With permission from Elsevier.)... 

Table 11.4 Comparison of EOF and migration times at different pH values for inorganic anions. Capillary 40 cm x 50 mm electrolyte 150 mM Li2S04, 0.05% PADDC, 20 mM borate for pH 8.5, or 20 mM sodium acetate for pH 5.0, or 20 mM HCI for pH 2.3 separation voltage -10 kV hydrostatic sampling 40 s at 10 cm height detection UV 214 nm EOF marker D.l. H2O.

Fig. 12 Effect of MeOH addition (in volume percentages) on the capillary electrophoresis separation of p-chloroamphetamine using 5 mM sulfated cyclofructan as the chiral selector. CE conditions buffer, 20 mM ammonium acetate +5 mM sulfated CF6 pH, 4.7 voltage, +25 kV capillary length, 35 cm capillary i.d., 50 p,m. First peak is EOF marker. The unit for the time axis (horizontal axis) is minute. Reprinted by permission of Wiley-VCH GmbH, Weinheim [44]...

The correct termination of lines by line delimiter characters and marks for an end of file have always been incompatible between DOS and its descendants, using carriage retum/linefeed (CR/LF) character pairs as end of line (EOL) markers and Z as end of file (EOF) marker, Macintosh systems (CR), and UNIX (LF, no EOF marker). Most... 

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