Qualitative Profiling

Gas chromatography coupled to mass spectrometry is a widely used analytical method [31] but does require prior reduction of the involatile N-oxides. Additionally, there are problems associated with some alkaloids that require prederivatization to enhance the GC characteristics. These requirements for prederivatization can adversely affect the GG-MS interpretation, especially at trace levels of alkaloids [32]. Gombined SPE-LC-MS approaches have provided methods for qualitative profiling and quantitative analysis of pyrrolizidine alkaloids and their N-oxides. 

Extraction of the pyrrolizidine alkaloids and their N-oxides from plant sources is a critical first step in LG-MS analysis. Some methods of extraction already described (Section 13.2) consist simply of treatment with aqueous methanol and, following microfiltration (0.45 p.m), immediate LC-MS analysis with no further treatment. However, the aqueous methanol treatment will extract more than just the alkaloids. 

Plant samples (e.g. leaves, flowers, pollen) are first extracted into methanol or dilute aqueous sulfuric add. In the case of the methanol extracts, the solvent is evaporated and the residue re-extracted with dilute aqueous sulfuric acid. The aqueous add 

13 LC-MS of Alkaloids Qualitative Profiling, Quantitative Analysis, and Structural Identification 

All of the following examples involved HPLC separation of the alkaloids on a reversed phase (C18 or C8) column (150 x 2.1mm i.d.) that was tolerant of high aqueous phases. The alkaloids were eluted using a combination of isocratic fiow and gradient flow (200 p,L/min) of 0.1 % formic acid in water (mobile phase A) and 0.1 % formic acid in acetonitrile (mobile phase B). The first isocratic stage (5 min) consisted of 93 % A and 7 % B. Then, over 15 min, the proportion of A B was altered in a linear fashion to 30 70. 

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Fig. 1.14. The qualitative profile of dependencies of equilibrium values of electric conductivity (curve /) and the tangent of inclination angle of VAC Ps (curves 2, 3) as a function of concentration of chemisorbed acceptors 2 - Inoj) 4co > a/2 3 - Inob co < o/2...

Since E depends itself on Ch,l. which in turn depends on the intrinsic kinetics, its value is not obvious to compute. For first-order reactions, the system formed with Eqs. (24) to (26), and with the given boundary conditions and corresponding to the qualitative profiles of Figure 45.2, must be solved. 

The setup of a calibration curve is not always feasible because pure standards of many clinically significant organic acids are not available commercially. This limitation underscores the importance of qualitative profile interpretation as the primary means by which to report organic acid results in clinical practice, rather than generating extensive lists of quantitative measurements of individual analytes. 

Thomas, A., Hopfgartner, G., Giroud, C., and Staub, C. (2009). Quantitative and qualitative profiling of endocannabinoids in human plasma using a triple quadrupole linear ion trap mass spectrometer with liquid chromatography. Rapid Commun. Mass Spectrom. 23, 629—638. 

The titration of Na2C03 with HC1 has the following qualitative profile ... 

The various operating modes used for an electron microprobe are qualitative analysis, qualitative profiles. X-ray mapping and quantitative analysis. 

This is a system based on the identification of microorganisms by the analysis of the culture medium for unique byproducts of that specific group of organisms. The advantages of this approach is that the sensitive, automated chemical systems, like glc or hplc, could be used. The disadvantages to this approach are obvious, i.e., that a tremendous database on the qualitative profile of those metabolic products would have to be available. Given the complexity of that analysis, it is unlikely that this is a practicable solution. 

Delicious taste and aroma are synonyms to fresh and good quality of almost any foodstuff and, undoubtedly, affect the consumer s final opinion and choice. Sensory characteristics of olive oil, a major component in the Mediterranean diet, represent the sum of the sensory parameters that integrate its complex and specific qualitative profile including various intrinsic and extrinsic factors such as cultivar (genetic), weather conditions, stage of ripeness, methods and/or system of harvest and storage (Table 5.13). Regulations and standards related to olive oil sensory evaluation include... 

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