Sample requirement alkaloids

In a further application of MI-SPE, theophylline could be separated from the structurally related caffeine by combining the specific extraction with pulsed elution, resulting in sharp baseline-separated peaks, which on the other hand was not possible when a theophylline imprinted polymer was used as stationary phase for HPLC. A detection limit of 120 ng mb1 was obtained, corresponding to a mass detection limit of only 2.4 ng [45]. This combination of techniques was also used for the determination of nicotine in tobacco. Nicotine is the main alkaloid in tobacco and is the focus of intensive HPLC or GC analyses due to its health risk to active and passive consumers. However, HPLC- and GC-techniques are time-consuming as well as expensive, due to the necessary pre-purification steps required because the sample matrices typically contain many other organic compounds besides nicotine. However, a simple pre-concentration step based on MI-SPE did allow faster determination of nicotine in tobacco samples. Mullett et al. obtained a detection limit of 1.8 jig ml 1 and a mass detection limit of 8.45 ng [95]. All these examples demonstrate the high potential of MI-SPE to become a broadly applicable sample pre-purification tool. 

The use of electrophotometry requires a sample preparation with a coloured solution. Together with an electrophotometer for alkaloid analysis, a constant light intensity and filter, as well as an electronic installation for measurement, must be used. The electrophotometry method is an application of both calorimetry and photometry in the same analysis. 

In 1995, the author and co-workers reported a comparison of the 13C-NMR spectra acquired for an 100 pg sample of the alkaloid cryptolepicarboline (13) using both a 3 mm micro-dual and heteronuclear Nano-probes.61 The two probe technologies gave roughly the same s/n ratios with the Nano-probe allowing the acquisition of the spectra in roughly one-third of the time required in a conventional 3 mm probe. Sample volumes were 40 and 140 pL, respectively. 

Fig. 19. Reversed-phase HPLC trace of a degraded 2.5 mg sample of the complex indo-loquinoline alkaloid cryptospirolepine (18) after storage in fi 6-DMSO for 10 years under uncontrolled conditions.243 No trace of the starting alkaloid remains. The two major impurities, labeled DP-1 and DP-2, constituted approximately 50% of the total sample. DP-1 was identified as the known alkaloid cryptolepinone (33) on the basis of 1H reference, COSY, and HSQC spectra. The elucidation of the structure of DP-2 required the utilization of a complete gamut of 2D-NMR spectra and the use of cryogenic NMR probe capabilities. (Reprinted with permission from Ref. 243. Copyright 2002, HeteroCorp.)...

Bush determined the four most important tobacco alkaloids (nicotine, nornicotine, anabasine and anatabine) using a 10 % DC 550 packed column on Chromosorb 60-80, and using isoquinoline as an internal standard. The alkaloids were extracted with benzene-chloroform (9 1) after treatment of the tobacco sample (1 g) with bariumhydroxide and water. The organic phase was concentrated and used for the gas chromatographic determination. Because of the great differences in the amounts of the minor alkaloids and nicotine in most tobacco samples, two extractions, each with an appropriate amount of internal standard, were required for a complete assay. The precision of the quantitative analysis on tobacco samples of different alkaloids is given in Table 5.6. 

A 10 mL sample of Ipecac was treated as in Experiment 15. For the titration, 5.00 mL of0.1500 N H2SO4 was added, which then required 31.60 mL of 0.025 N NaOH to reach the endpoint. The blank was 2.20 mL. How many mg of Ipecac alkaloids, calculated as emetine, were present This bottle had the same label as that in the example calculation. What are your conclusions ... 

Although lycium fruit has been reported to contain the alkaloid atropine up to 0.95% (Harsh 1989), the presence of tro-pane alkaloids has been disputed (Frohne and Pfander 1997 Merz and Stolte 1960), and a more recent analysis indicates that the atropine content of dried lycium fruit is very low, generally less than 10 parts per billion (ppb), with the highest level of analyzed fruit containing 19 ppb. Severe atropine intoxication with the examined lycium fruit samples would require the unrealistic consumption of several tons of berries (Adams et al. 2006). 

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