Analysis of chromatograms

Area analysis of chromatograms is familiar to the chromatographer. The assumption is made that the area of a peak is proportional to the mass of the component present. The spectrophotometric detector is set at about 280 nm to detect the aromatic residues or at 210 to 230 nm to detect the peptide bond. The absorbance at 280 may be influenced by peptide composition, while the absorbance near 220 nm is more closely correlated to mass. 

The analysis of chromatograms has disclosed that the maximum chemiluminescent activity corresponds to the spot of dianthrol (DA, with retention index Rf = 0.25) rather than to that of peroxide species (Rf = 0.37), whose intervention into the anthrone photochemiluminescence process was suggested in the literature. Thus, DA, which exists in two isomeric forms (Scheme 3), furnishes the relevant high-energy... 

Petroleum Industry Gas chromatography is ideally suited for the analysis of petroleum products, including gasoline, diesel fuel, and oil. A typical chromatogram for the analysis of unleaded gasoline is shown in Figure 12.25d. 

Examples of the application of HPLC to the analysis of (a) acetaminophen, salicylic acid, and caffeine (b) chlorinated pesticides (c) tricyclic antidepressants and (d) peptides. (Chromatograms courtesy of Alltech Associates, Inc. Deerfield, IL). 

This experiment describes the quantitative analysis of the asthma medication Quadrinal for the active ingredients theophylline, salicylic acid, phenobarbital, ephedrine HGl, and potassium iodide. Separations are carried out using a Gi8 column with a mobile phase of 19% v/v acetonitrile, 80% v/v water, and 1% acetic acid. A small amount of triethylamine (0.03% v/v) is included to ensure the elution of ephedrine HGl. A UV detector set to 254 nm is used to record the chromatogram. 

A typical TIC chromatogram from an analysis of peptides resulting from enzymatic digest of myoglobin. The peaks represent individual peptides eluting from an LC column and being mass measured by a spectrometer coupled to it through a dynamic-FAB inlet/ion source. 

Table 9,4 Data for the Analysis of the Gel Permeation Chromatogram of a Poly disperse Polymer Used in Example 9.7...

Specifications, Analysis, and Toxicity. Dicyandiamide is identified quaHtatively by paper chromatography and quantitatively by ultraviolet spectrometry of the chromatogram. More commonly, total nitrogen analysis is used as a purity control or the dicyandiamide is converted by hydrolysis to guanylurea, which is determined gravimetrically as the nickel salt (50). Methods based on the precipitation of silver dicyandiamide picrate are sometimes used (51). Dicyandiamide can also be titrated with tetrabutylammonium hydroxide ia pyridine solution. Table 4 gives a typical analysis of a commercial sample. Dicyandiamide is essentially nontoxic. It may, however, cause dermatitis. 

Recently the Ar /He — Ne lasers have been employed for the analysis of thin-layei chromatograms [259 — 261]. However, instruments of this type have not yet comt into general use. 

It is only since this method has come into use that the precise quantitative analysis of thin-layer chromatograms has become possible. For the increased... 

Every chromatographic investigation begins with the preparation of the sample and the chromatographic system. This is followed by the crux of the separation process (development of the chromatogram) which is in turn followed by the visualization of the separated substances and the preservation of the chromatogram and finally by the analysis of the results. 

In situ quantitation The fluorimetric analysis of monoterpene glucosides could be performed with advantage at 2exc = 313 nm and 2 > 390 nm. The detection limits of arbutin and L-menthylglucoside were 1 — 5 ng and 15 ng substance per chromatogram respectively (Fig. 1). 

The result was that light blue fluorescent zones were visible under long-wavelength U V light (2 = 365 nm). Before fluorimetric analysis the chromatogram was dipped for 1 s into liquid paraffin — n-hexane (1 + 2) to enhance (by a factor of 2 to 8) and stabilize the intensity of the fluorescence and then dried for 1 min in a stream of cold air. The quantitation (2e,c = 365 nm An > 430 nm) was carried out after 1 h since it was only then that the fluorescence intensity had stabilized. 

FIGURE I 1.3 Analysis of poly(l, 4-butylene terephthalate) usinga Waters Alliance narrow-bore GPC system. Columns 4.6 X 300 mm Styragel HR 2, HR 3, and HR 4. Mobile phase hexafluoroisopropanol. 0.35 ml/min at 30 C. (Chromatogram courtesy of Peter Alden, Waters Corp.)... 

FIGURE I 1.7 Chromatogram of an amine-based epoxy resin. The analysis of an amine-based epoxy resin was obtained on a column bank of 7.8 x 300 mm Styragel HR O.S, HR I, HR 2, and HR 3 columns. (Courtesy of Waters Corp.)... 

The above theoretical analysis of the total number of resolvable components in a complex mixture has shown that in LC, relative to the maximum peak content or peak capacity for closely spaced peaks, a random chromatogram will never contain more than about 37% of its potential peaks and furthermore that only 18% of such components will emerge as single-component peaks having a minimum specified resolution with respect to the neighbouring peaks. 

Figure 10.3 Gas cliromatograms of a cold-pressed lemon oil obtained (a) with an SE-52 column in the stand-by position and (b) with the same column showing the five heart-cuts (c) shows the GC-GC chiral chromatogram of the ti ansfeired components. The asterisks in (b) indicate electric spikes coming from the valve switcliing. The conditions were as follows SE-52 pre-column, 30 m, 0.32 mm i.d., 0.40 - 0.45 p.m film tliickness cairier gas He, 90 KPa (stand-by position) and 170 KPa (cut position) oven temperature, 45 °C (6 min)-240 °C at 2 °C/min diethyl-tert-butyl-/3-cyclodextrin column, 25 m X 0.25 mm i.d., 0.25 p.m film thickness cairier gas He, 110 KPa (stand-by position) and 5 KPa (cut position) oven temperature, 45 °C (6 min), rising to 90 °C (10 min) at 2 °C/min, and then to 230 °C at 2 °C/min. Reprinted from Journal of High Resolution Chromatography, 22, L. Mondello et al, Multidimensional capillary GC-GC for the analysis of real complex samples. Part IV. Enantiomeric distribution of monoterpene hydrocarbons and monoterpene alcohols of lemon oils , pp. 350-356, 1999, with permission from Wiley-VCH.

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