Fingerprint derivative detection

Subjecting the total matrix to chemical treatment may be an effective method for detection of fingerprint derivatives, without actual isolation of the analytes. Thus, for example, colored yams can be tested for the presence of forbidden azo dyes by subjecting them to partial reduction with sodium dithionite, followed by FTIR of the reduced yam and detecting the characteristic peaks of restricted PAA. This method was applied to forensic testing of textiles which were dyed with forbidden azo dyes (Section n.B.5)196. 

Figure 13.20 HPLC of amino acid derivatives detected by 254 nm UV absorption (a) 200 pmol of PTC-amino acid standard, including pbospboserine (PH-S), pbospbothreonine (PH-T), bydroxy-proline (OH-P), galactosamine (Gal), norleucine (NLE, 1 nmol internal standard), excess reagent (Re), and other amino acids designated by one letter codes listed in Fig. 13.19 and (b) Analysis of a human fingerprint, taken up from a watchglass using a mixture of water and ethanol. (Courtesy of National Gallery of Art and the Andrew W. Mellon Foundation.) (Cazes, used with permission.)...

Rycroft et al. (1999) identihed the major components of plants from six locations in western Scotland and four from the Azores using nuclear magnetic resonance (NMR) fingerprinting and GC-MS. The terpene P-phellandrene [129], which may be responsible for the aroma of material crushed in the held, was detected in all specimens. The major components, which appear in Fig. 5.6, were shown to be methyl eveminate [444], the four methyl orcellinate derivatives [445 8], the two 9,10-dihydrophenanthrene derivatives [449] and [450], the newly described phthalide killamiensolide [451], and the bibenzyl [453]. Methyl eveminate was the major compound in all 10 specimens other compounds were more varied in their occurrence. Killamiensolide was not isolated as such but was detected when extracts were acetylated yielding, among other compounds, [452]. The presence of the bibenzyl compound [453] in more than trace amounts in P. killarniensis raises the possibility that it represents contamination from P. spinulosa with which it was growing at the one site. 

A major advantage of infrared absorption spectroscopy derives from the characteristic fingerprints associated with infrared-active molecules. On the other hand, interferences from common atmospheric components such as C02 and HzO are significant, so that the sensitivity and detection limits that can be obtained are useful primarily for polluted urban air situations. For atmospheric work, long optical path lengths are needed. 

Fingerprinting methods such as the anthocyanin methods and the Kirksey method for polyphenols (Kirksey el al., 1995) offer good ways to check for the addition of other fruits in a product. As the adulterators have become more sophisticated in the approaches that they use to extend juices, there has been a need for more complex methods of analysis. This means that it is now not uncommon to have to use fingerprinting techniques and isotopic methods to detect the most sophisticated forms of adulteration. These sophisticated analytical methods can even involve detection of the isotope ratios within a class of compounds such as sugars (Hammond el al., 1998). Using the RSSL 13C-IRIS approach, which was developed with financial support from the UK Food Standards Agency, it was possible to reduce the detection limit for the addition of C4-derived sugars to juices by about a factor of two. 

Carbonized coal products have a unique fingerprint by both GC and fluorescence analyses. Both these fingerprints confirm that sediments from the Elizabeth River are contaminated with carbonized coal products and allow for the detection of carbonized coal hydrocarbons, even in the presence of petroleum-derived hydrocarbons. Fluorescence allows for the rapid analysis of more samples and shows the contamination within the Elizabeth River to be widespread. Carbonized coal products in the sediments may constitute a chronic long-term source of PNA s to the water column. 

Moreover, a rapid diagnostic method for analysing the three new cytokinins (1 MeZ, its 9-P-D-riboside and 2 deOZR) was developed to detect them in complex samples. The natural cytokinins and some of their above-mentioned derivatives and analogues, were characterised by fast atom bombardment tandem mass spectrometry (FAB MS MS). The protonated molecular ions of the examined cytokinins could be fingerprinted from breakdown patterns of their gaseous unimolecular... 

Re appears as a distinct peak, indicates that derivatization took place in precolumn mode. The presence of altered or metabolized derivatives of the 20 essential amino acids is characteristic of actual biological samples. The top trace is of a standard mixture of 200 pM concentration amino acids, while the lower one is from fingerprint oils extracted by water and ethanol from a glass surface. This illustrates impressive sensitivity for HPLC with UV/VIS detection. Twenty-fold greater sensitivity is possible when using fluorescent detectors with OPA (cf. Table 13.2) derivatives of amino acids. 

The variation between individuals in such DNA profiles is so great that we are unlikely, in any reasonable sample size, to see the same pattern duplicated in unrelated individuals. Thus we cannot arrive empirically at an estimate of the low probability of two DNA profiles matching by chance. We have to use statistical models to estimate this probability, based on reasonable genetic assumptions and measurements that can be derived from the available data. The quantities normally used to measure DNA fingerprint information are x, the bandsharing, which is the proportion of bands shared by unrelated individuals in the population, and n, which is the mean number of scorable bands detected in the profiles. An inaccurate but generally statistically conservative assumption that is often made is that x is constant for all... 

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