Amino organic trace analysis

Microanalysis, the detection and identification of materials present in small size but relatively high concentration, is distinct from trace analysis, which is concerned with the characterization of small concentrations of material. Organic microanalysis is usually taken to mean elemental analysis (primarily C, H, O, N, P, S, Cl, Br, 1, and Si), and functional group analysis (acetyl, carboxyl, benzoyl, amino, nitro, hydroxy, etc.) on samples usually 1-10 mg in size. The semiquantitative results, accurate to about 10%, serve as a measure of impurities, or inhomogeneity, or for structure determination in solid organic substances. Accurate results of 1 % or better may be expected when large (1 g) samples are taken for analysis and the entire chemical apparatus is scaled upward in size. However, small samples take less time to analyze, so the micro methods are more popular than macro methods. 

Trace amounts of bromine in sodium diclofenac, sodium (2-[(2, 6-dichlorophenyl)amino] phenyl acetate, have been determined using XRF [82], since the drug substance should not contain more than 100 ppm of organic bromine remaining after the completion of the chemical synthesis. Pellets containing the analyte were compressed over a boric acid support, which yielded stable samples for analysis, and selected XRF spectra obtained in this study are shown in Fig. 7.19. It was found that samples from the Far East contained over 4000 ppm of organic bromine, various samples from Europe contained about 500 ppm, while samples from an Italian source contained less than 10 ppm of organic bromine. 

The collection of a reference material for trace metals could complement collection of samples for other priority analytes including DOM and DOC. Seawater used for DOM analysis can also be collected in Teflon , for example. Although samples for DOM are not normally stored in plastic bottles (as the iron reference material would be), releases of plasticizers are minimal and are not expected to interfere with the detection of individual organic compounds such as amino acids and sugars. 

On a relative basis, i.e. residues per 1000, there is virtually no one species like the other. In contrast, different shell samples from the same species and obtained from the same natural habitat yield identical amino acid patterns. It is of interest that (1) the structure of carbonates (aragonite-calcite-vaterite), (2) the content in trace elements, and (3) the stable isotope distribution are markedly effected by fluctuations in salinity, water temperature, Eh/pH conditions, and some anthropogenic factors. The same environmental parameters determine to a certain degree the chemical composition of the shell organic matrix. This feature suggests a cause-effect relationship between mineralogy and organic chemistry of a shell. In the final analysis, however, it is simply a reflection of the environmentally-controlled dynamics of the cell. 

Many different types of fruit and vegetable crops and other processed foods are analysed for a variety of trace organics both for impurities (such as pesticides) and for content (e.g. amino acids, lipids, etc.). As with soil, it is important to take a representative sample for analysis. 

---