Plant material analytical methodology

The relatively free-wheeling synthesis selection phase through the END gives way to a much more controlled development phase, wherein the quality of the Toxicology Batch (and especially impurity levels) dictates the quality of the API batches to be produced, slowing process change. Analytical methodologies and specifications for the API, intermediates, and raw materials become more refined. Impurity and stability profiles are established. Process control mechanisms are developed and plant SOPs incorporate the better controls. The NDA process slowly takes shape. 

For all analytical methods the quality of the results ultimately relates back to the chemical purity of the very best available SRM and to the linearity of the correlation curve for the experimentally measured property vs. the SRM concentration. For substances that are naturally chiral there is the additional very serious concern about enantiomeric purity. The determination of an enantiomer whether for an enantiomeric purity test, or for an enantiomeric ratio or excess test in the study of a partial racemic mixture, is one of the more difficult analytical problems. To actually report the enantiomeric purity of an enantiomer as better than 99% is truly beyond the capability of current analytical methodology [31], for after all few substances ever have a chemical purity that is guaranteed to be greater than 99%. So, as mentioned earlier, one has to accept the fact that the results are measured relative to an enantiopurity of an SRM that is defined to be 100%. This limitation of course impacts on the true meaning of a calculated enantioexcess, and to a much lesser degree perhaps, in assays of chiral substances extracted from plant materials using calibration data that were obtained for synthetic SRM s. 

Fahmy, T.M., Pulaitis, M.E., Johnson, D.M., McNally, M.E.P., Modifier effects in the supercritical fluid extraction of solutes from clay, soil, and plant materials. Anal. Chem., 65 (10), 1462-1469,1993. Langenfeld, J.J., Hawthorne, S.B., Miller, D.J., Pawliszyn, J., Role of modifiers for analytical scale supercritical fluid extraction of environmental samples. Anal. Chem., 66(6), 909-916,1994. Hawthorne, S.B., Methodology for off-line supercritical fluid extraction. In Supercritical Fluid Extraction and Its Use in Chromatographic Sample Preparation, Westwood S.A. (Ed.), Blackie Academic and Professional, 39-64, 1993. 

Naturally, these three approaches to developments in analytical techniques for plant materials cannot exclude some small overlap and repetition but careful selection of the authors of individual chapters, according to their expertise and experience with the specific methodological technique, the group of substances to be analyzed, or the plant material which is the subject of chemical and physical analysis, guarantees that recent developments in analytical methodology are described in an optimal way. 

It is with the topic of analyte determination in foods by the technique of analytical AAS that this chapter is concerned. Analyte quantitation (d above) by this technique is thus the main thrust of this treatment, but of necessity, the intimately related procedures of sample treatment (b) and analyte separation and manipulation (c) will also be discussed insofar as they bear on quantitative measurement by AAS. Food for human consumption is the main concern of this chapter. Peripheral discussion, however, of allied commodities such as plants and animal feedstuffs, is included to make the treatment more comprehensive, especially in areas where there is a dearth of publications relating to food-analysis applications of atomic spectrometry. For detailed accounts of methodologies bearing on such related materials, the reader is referred to the other chapters in this volume. 

As research progresses toward a commercial venture, there are points in time when the importance of the chemical substance, formulation or the fabricated item must he evaluated. Althou each company may have its own system for evaluation, more and more individuals become involved as the cycle progresses. Multi-disciplinary resources and talents are needed to deal with procurement, with the biological impact or potential hazards from the material, with the formulation or fabrication methodology that may he needed, and even with how it will he marketed and what segments of sociely will find it useful. Thus, industrial R D involves managing a broad range of resources — dollars, professional skills (people) and facilities (analytical equipment, pilot plants, etc.). 

Some plant science researchers have found it useful to compare activation analysis methodology with other analytical methods for example, Van Puymbroeck et al. (959) compared the determination of trace Sr in biological materials (plants and soils) by atomic absorption, dame spectrophotometry and activation analysis, and concluded that, although atomic absorption could be more economical, activation analysis was more sensitive. Barbe (52) also used a comparison of flame spectrophotometry and activation analysis in his determinations of Sr in vegetables and his conclusions were similar to those of Van Puymbroeck. Beyer-mann (63) showed that activation analysis was more sensitive than X-ray fluorescence analysis for the determination of nanogram amounts of Br in biological materials. 

The methodology used to analyze these compounds in plant-based materials, generally, includes a series of steps ranging from exhaustive solvent extraction, clean-up of extracts, and preconcentration procedures to simple filtration and centrifugation in liquid samples. After the extraction procedures, the phenolic compounds are characterized and quantified [7, 8]. Various complex analytical methods have been used for the determination of these compounds in natural samples and the most important of them are described in detail in this chapter. 

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