Peak chromatography

Consider the liquid chromatography peak shown in figure 1. 

FIGURE 10.13 The TLC profiles of labeled peaks isolated from [U- C]ascorbic-acid-modified calf lens protein obtained from Bio-Gel P-2 chromatography. Peaks 2 to 7 were spotted on a preparative silica gel TLC plate and developed with ethanol/ammonia (7 3, v/v). The fluorescence in each lane was detected by irradiation with a Wood s lamp at 360 nm, and the pattern of radioactivity was determined by scanning the plate with AMBIS imaging system. (Reprinted with permission from Cheng, R. et al., Biochim. Biophys. Acta, 1537, 14-26, 2001. Copyright (2001) Elsevier.)... 

P.J. Gemperline, A priori estimates of the elution profiles of the pure components in overlapped liquid chromatography peaks using target factor analysis. J. Chem. Inf. Comput. Sci., 24 (1984) 206-212. 

Figure 5 Separation of the plasticisers present in PVC cling film by size exclusion chromatography. (Peaks left to right, identified by their infrared spectra, obtained using LC-Transform equipment, as DEHA, ESBO and PVC.)...

A representative example of this process is shown in Fig. 2. The spectra of the analyte peaks can be measured at the upslope, the top, and at the downslope, or the whole spectrum of the chromatography peak can be compared. In the latter case, the term totalpeak purity is used, and a purity curve of the peak can also be recorded. These operations can be performed by a HPLC system equipped with a DAD detector [13], or for TLC a densitometer that can measure the UV-Vis spectrum of the analyte spot should be used. If the value of the purity is 0.000 0.8900, it is not pure, and a purity of 0.9000-0.9500 means that the peak is contaminated (Shimadzu Class-VP, Chromatography Data System). 

FIGURE 11.20 An illustration of how the area of an instrumental chromatography peak is determined by integration. The series of digital values acquired by the data system, represented by the vertical lines, are summed. 

Draw an example of an instrumental chromatography peak and show in your drawing and describe in words the specific method by which peak area is measured by integration. 

FIGURE 13.9 The HPLC diode array UV absorbance detector. When a mixture component elutes from the column, not only the chromatography peak but the entire UV absorption spectrum for that component can be recorded. 

We have already briefly described a popular application of amperometry in Chapter 13. This was the electrochemical detector used in HPLC methods. In this application, the eluting mobile phase flows across the working electrode embedded in the wall of the detector flow cell. With a constant potential applied to the electrode (one sufficient to cause oxidation or reduction of mixture components), a current is detected when a mixture component elutes. This current translates into the chromatography peak... 

Gas chromatography retention time of PCB congener relative to the retention time of the reference standard octachloronaphthalene on a capillary column of SE-54. Gas chromatography peak area response of PCB relative to peak area of 1 ng octachloronaphthalene. 

There are many methods used to calculate efficiency. All methods give the same results with ideal, Gaussian peaks. Real chromatography peaks tend to tail on the backside of the peak (away from the injection mark on the... 

Micro- and nano-HPLC systems (Fig. 15.11) rely on small-diameter and capillary columns packed with high-efficiency packing materials and very slow flow rates to produce concentrated solutions and sharp chromatography peaks to feed electrospray interfaces for mass spectrometers. 

Figure 7. Size Exclusion Chromatography peak average diameters for three batch runs with different emulsifier levels runs BIO — Bll are replications.

The methods of quantitative analysis are essentially tiiose inherited from gas chromatography. Peak hei t or pe area can be measured, either manually or with electronic devices. Peak height measiu-ements have the advantage of simplicity but are sensitive to changes in peak shape peak area measurements should always be used where peaks are broad and tailing. 

Figure 11. The GLC C20 region of a menhaden omega-3 PUFA concentrate (ethyl ester) (a) before and (b) after heat treatment at 220° C, and (c) the 20 5 region of an artifact concentrate isolated by AgN03 column chromatography. Peaks A-E refer to artifacts formed after heat treatment. Analysis on a SUPELCOWAX-10 fused-silica capillary column operated isothermally at 195X1. Note that components B-E fall into the region where several 22 1 isomers may be found (cf. Figs. 5 and 7). From (77).

Fig.l The effect of the background conductivity suppression on the monitored signal of the analyte anions, after separation by means of ion chromatography. Peaks 1 = fluoride, 2 = nitrate, 3 = sulfate. 

Villermaux, J. 1974. Deformation of chromatography peaks under the influence of mass transfer phenomena. J. Chromotogr. Sci. 12 822-831. 

The values correspond to effluent volumes of size exclusion chromatography peaks (column with CL-Sepharose 2B resin eluent - 0.2 M NaCl temperature - 20 °C). 

Nakatsu [213] described a fraction collector controller for separate collecting of liquid chromatography peaks. 

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