Caffeine HPLC chromatogram

Obtain HPLC chromatograms of the calibration standards by injecting 20 jTL of each. There should be two peaks. The benzoate peak will be much smaller than the caffeine peak, and the detector attenuation will need to be changed after the caffeine has eluted. Record the peak size vs. concentration data. 

Fig. 2.62. HPLC chromatogram of (a) jasmin (green) tea, (b) Fujian Oolong tea, (c) pu-erh tea and (d) black tea at 280 nm. Peak identification 1 = gallic acid (GA) 2 = (-)-epigallocatechin (EGC) 3 = (-)-epigallocatechin gallate (EGCG) 4 = epicatechin (EC) 5 = (-)-epicatechin gallate (ECG) 6 = caffeine (CA) 7 = ( — )-catechin gallate (CG). Reprinted with permission from Y. Zuo et al. [178].

Figure 2. HPLC chromatogram of caffeine standard (top), coffee (middle) and Honeybush (bottom). The chromatograms for all of the African herbal teas also were devoid of the caffeine peak.

As catechins are good UV chromophores with absorption maxima at 210 and 270-280 nm, UV and diode array detectors (DAD) are traditionally the most popular detectors employed for their determination in tea infusions. A typical HPLC chromatogram for green tea extract with low caffeine content is shown in figure 6.1. 

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). 

FIGURE 16 The chromatogram of an injection of a caffeine solution without the column showing the instrumental bandwidth of a Waters Alliance HPLC system with a 966 PDA detector with a standard flow cell. 

FIGURE 8 Example of HPLC-FTIR chromatograms for three drugs, acetaminophen, caffeine and dodecanolactam (top). Corresponding FTIR spectra are shown at the bottom (reproduced with permission from Bourne, I998). 

FIGURE 10.3 Comparison of mass spectra obtained from online HPTLC-MS and HPTLC-HPLC-MS analysis (a) HPTLC-MS chronogram and mass spectrum of the suspected zone of Sudan 1 and (b) HPTLC-HPLC-MS chromatogram of the suspected zone of Sudan I and mass spectra of the chromatographically separated peaks on the monolithic RP 18e column, indicating caffeine and Sudan I. 

The HPLC determination of A -methylnicotinic acid has been reported by Trugo et al. (49). Chromatograms of a reference mixmre of A -methylnicotinic acid, theobromine, theophylline, and caffeine and of an extract of instant coffee are shown in Figure 17. 

Figures Chromatograms on MIL-53(Al)-packed column (7-cm longx4.6-mm i.d.) for RP HPLC separation using CHjCN/HjO as mobile phase at l.OmLmin b (a) ethylbenzene and toluene (b) PAHs (c) thiourea (1), phenol (2), aniline (3), benzaldehyde (4), bromobenzene (5), naphthalene (6) (d) o-benzenediol, m-benzenediol, and p-benzenediol (e) aniline, N,N-dimethylaniline, and m-nitroaniline (f) xanthine, theophylline, and caffeine. Mobile phase composition (CHjCN/HjO, v/v) (a) 7 3 (b) 10 0 (c) 6 4 (d) 1 9 (e) 9 1 (f) 5 5. UV detection at 210 run (a, c), 256 run (b), 70 run (f), and 280 nm (d, e). (Reproduced from Ref 69 with permission of The Royal Society of Chemistry. DOI 10.1039/C2AN15925B.)...

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