Electropherograms

Caffeine in tea and coffee is determined by CZE using nicotine as an internal standard. The buffer solution is 50 mM sodium borate adjusted to pH 8.5 with H3PO4. A UV detector set to 214 nm is used to record the electropherograms. 

Fig. Electropherogram of a) catechin standards, b) green tea sample prepared in 50 % methanol using liquid extraction...

Fig. 2. Electropherogram of real sample (homogenize of Drosophila flies heads). Electrolyte solution 7 mM sodium tetraborate, pH 8.14...

A practical application of SEE-CEST coupling is shown in Eigure 6.13, which displays the electropherogram obtained for a tomato sample contaminated with a pesticide, i.e. carbaryl. The sample was placed in the SEE cell, extracted with CO2... 

Figure 6.13 SEE-MEKC electropherogram of the pesticide carbaryl in a tomato sample the peak assigned number (4) coiresponds to the migration time of carbaryl. (from ref. 58).

Electropherograms of a urine sample (8 ml) spiked with non-steroidal anti-inflammatory drugs (10 p-g/ml each) after direct CE analysis (b) and at-line SPE-CE (c). Peak identification is as follows I, ibuprofen N, naproxen K, ketoprofen P, flurbiprofen. Reprinted from Journal of Chromatography, 6 719, J. R. Veraait et al., At-line solid-phase exti action for capillary electrophoresis application to negatively charged solutes, pp. 199-208, copyright 1998, with permission from Elsevier Science. 

Figure 7-11. Normal and pathologic patterns of lactate dehydrogenase (LDH) isozymes in human serum. LDH isozymes of serum were separated by electrophoresis and visualized using the coupled reaction scheme shown on the left. (NBT, nitroblue tetrazolium PMS, phenazine methylsulfate). At right is shown the stained electropherogram. Pattern A is serum from a patient with a myocardial infarct B is normal serum and C is serum from a patient with liver disease. Arabic numerals denote specific LDH isozymes.

Capillary electrophoresis offers several useful methods for (i) fast, highly efficient separations of ionic species (ii) fast separations of macromolecules (biopolymers) and (iii) development of small volume separations-based sensors. The very low-solvent flow (l-10nL min-1) CE technique, which is capable of providing exceptional separation efficiencies, places great demands on injection, detection and the other processes involved. The total volume of the capillaries typically used in CE is a few microlitres. CE instrumentation must deliver nL volumes reproducibly every time. The peak width of an analyte obtained from an electropherogram depends not only on the bandwidth of the analyte in the capillary but also on the migration rate of the analyte. 

FIGURE 16.2 Representative base peak electropherograms from CZE runs of RPLC fractions, (a) Fraction 15 (5 peptide identifications) and (b) fraction 20 (19 peptide identifications). Column, bare fused silica capillary, 60 cm x 180 pm ODx30pm i.d. separation voltage, 15 kV observed CZE current, 1.91 p.A running electrolyte, 200 mm acetic acid + 10% isopropanol temperature, 22°C injection time, 10 s at 2 psi ( 4 nL total injection volume) supplementary pressure, 2 psi flow rate, 25nL/min spray voltage, 1.5 kV (reprinted with permission from Electrophoresis). 

A similar analysis of cochineal can be performed with the use of CE with ESI MS detection. The results are similar to those obtained with HPLC MS.[20] In the lac dye extract, the signal of laccaic acid A is found in the mass spectrum as the dominant one at m/ z 536. However, a second peak is observed on the electropherogram, and the eluted substance can be identified as laccaic acid E, on account of the mass spectrum which consists of the following signals at m/z 494 [M H], 476 [M H20 H] and 450 [M C02 H]. ... 

Figure 13.3 Electropherogram (total ion current) of the madder lake extract and ESI mass spectra taken at the apex of the peaks. Identified colourants alizarin, m/z 239 purpurin, m/z 255. Reproduced from M. Puchalska, M. Orlihska, M.A. Ackacha, K. Pofec Pawlak and M. Jarosz. J. Mass Spectrom., 38, 1252 1258 (2003). By permission of John Wiley ...

Figure 11 Electropherogram of a mixture of five amino acids using indirect CL detection. Conditions 21-kV separation voltage, and 2 s at 21 kV for sample injection sample concentration 0.5 mM of each amino acid. Peak identities (1) arginine (2) leucine (3) serine (4) cysteine (5) aspartic acid. (From Ref. 86, with permission.)...

Figure 13 Electropherogram of selected amino acids with end-column addition of 1 mM Ru (bpy)32+. Separation conditions 20 kV with injection of analytes for 8 s at 20 kV. Capillary, 75 im id, 62 cm long with a 4-cm detection capillary. Buffer 15 mM borate, pH 9.5. The electrode used for in situ generation of Ru(bpy)33+ was a 35-jlm-diameter carbon fiber, 3 mm long held at 1.15 V versus a saturated calomel electrode. The PMT was biased at 900 V. Peak identification (1) 100 fmol TEA, (2) 70 fmol proline (3) 1.6 pmol valine, (4) 50 pmol serine. Injection points. (From Ref. 97, with permission.)...

Electropherogram of blood serum on cellulose acetate. (Buffer 0.50 M barbitone, pH = 8.6)... 

Eq. 17.42 is the expression of the resolution for CE in electrophoretic terms. However, the application of this expression for the calculation of Rs in practice is limited because of D,. The diffusion coefficient of different compounds in different media is not always available. Therefore, the resolution is frequently calculated with an expression that employs the width of the peaks obtained in an electropherogram. This way of working results in resolution values that are more realistic as all possible variances are considered (not only longitudinal diffusion in Eq. 17.42). Assuming that the migrating zones have a Gaussian distribution, the resolution can be expressed as follows ... 

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