HPLC chromatogram profile after

Figure 2 HPLC chromatogram profile of a solution containing (-)-epicatechin, malvidin 3-O-glucoside and acetaldehyde recorded after 24 hours of reaction (up) and UV visible spectra of the major pigments detected in the solution (middle and bottom), (mv 3glc malvidin 3-0-glucoside). (Adapted with permission from reference 31. Copyright 2002 American Chemical Society.)...

Figure 4.18. Peak-size correlation in an HPLC-chromatogram. The impurity profile of a chemical intermediate shown in the middle contains peaks that betray the presence of at least two reaction pathways. The strength of the correlation between peak areas is schematically indicated by the thickness of the horizontal lines below the chromatogram. The top panel gives the mean and standard deviation of some peak areas (n = 21) the two groups of peaks immediately before and after the main peak were integrated as peak groups.

Fig. 1. Example of UV absorbence profiles (280 nm) of RP-HPLC chromatograms of human LVV-hemorphin-7 (LVVH7) products after 10 min of incubation with (A) rat brain homogenate and (B) rat brain microsomal fraction at 37°C. The figures show how degradation is more prominent in the microsomal fraction of brain tissue, i.e., how the original LVVH7 peak is reduced, while degradation products 1 and 3, PI and P3, increases in B compared to A. Control chromatograms with homogenate and microsomal fraction with no added human LVVH7 are represented in small windows (modified from ref. 27).

A reaction mixture containing IMP, aspartic acid, and GTP was prepared, and the reaction was started by the addition of purified sAMP synthetase. As the incubation proceeded, samples were removed and analyzed by HPLC. As shown in Figure 10.9, the chromatograms reveal the presence of the substrates and the formation of sAMP. After incubation for 20 minutes, the multienzyme system was reconstituted by the addition of a sample of sAMP lyase to the reaction. The reconstituted system was incubated for an additional 10 minutes, and a sample removed at that time was analyzed by HPLC. The profile (Fig. 10.9) illustrates a decline in the level of sAMP and the appearance of a new peak, AMP, confirming the successful reconstitution of this two-enzyme system. 

Figure 10.9 HPLC elution profiles of adenylosuccinate synthetase incubation mixtures. The reaction was initiated by the addition of 1.25 /xmol of aspartate (pH 7.4). At 5-minute intervals, 20 /xL samples were injected onto the HPLC reversed-phase column and eluted. After 10 minutes of incubation (arrow), sAMP lyase was added to the incubation mixture along with 10 nmol of EDTA. Inset Time-dependent utilization of IMP and the formation of sAMP, as determined by integration of the respective peaks from the HPLC chromatograms. (From Jahngen and Rossomando, 1984.)...

Figure 4 Reversed-phase HPLC elution profiles of tocopherols (panel A), retinoids (B), and carotenoids (C) present in human plasma (200 pL). Blood was collected 3 h after an oral dose of retinoic acid. The chromatogram was obtained by use of gradient elution (Table 3). Peak identification 2, 4-oxo-retinoic acid 4, retinoyl P-glucuronide 7, retinoic acid 8, retinol 9, retinyl acetate (internal standard) 15, butylated hydroxy toluene 16, y-tocopherol 17, a-tocopherol 18, free bilirubin 19, lutein 20, zeaxanthin 21, 2, 3 -anhydrolutein 22, P-cryptoxanthin 23, lycopene 24, a-carotene 25, P-carotene. (From Ref. 73.)...

HPLC-based DPPH activity profiling The sample is first analyzed by HPLC to obtain a screening of the compounds. Next, the sample reacts with DPPH and is injected into HPLC. The peak areas of antioxidant compounds are reduced or disappear in the HPLC chromatogram after their reaction with DPPH, and for those without antioxidant activities, the peak areas remain almost constant (Xie et ak, 2005 Zhang et ak, 2011 Shi et ak, 2012). In some works, different amounts of the sample are reacted with DPPH to calculate the ICjo, and then the wavelength selected in the HPLC detector is that corresponding to the DPPH absorption (Chandrasekar et ak, 2006 Helmja et ak, 2009). 

Is depicted the HPLC profile from a naturally contaminated peanut sample. This sample when analyzed contained 943 ppb (ug/kg) total aflatoxins. This chromatogram demonstrates that aflatoxins can be identified without any further deriv-atlzatlon by using a diode array detector after the affinity clean-up procedure and reversed phase HPLC. This detector obtains the spectrum of chromatographic peaks. Since as little as 2 ppb In the diet of rats (2) has been found to produce liver tumors following life time exposure, the levels of aflatoxins in the diets of people eating this level of contaminated foods would be of serious concern. 

The methods developed for this work allowed the direct analysis of the total reaction products by diode array HPLC. This was important since, during the development of procedures, it became apparent that the chromatograms obtained on injecting fresh model systems after 6 and 15 min heating varied when injections were repeated 70 min later (the HPLC run time) with the sample stored in the autosampler at room temperature. This suggested that any sample pre-treatment prior to HPLC would be likely to result in a modified reaction products profile. Chromatograms were obtained at 254 and 280 nm (for detection of colorless compounds), 360 nm (for detection of pale yellow components) and 460 nm (for colored material). 

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