Degradation products, analysis

The precision of the Padley and Timms (1980) and Young s (1984) procedures has been improved by the incorporation of data derived from sterol degradation product analysis which helps to identify the type of fat present and therefore narrows the range along the C54-C50 band in which the fat falls (Macarthur el al., 2000). These improvements to the method have been proposed for adoption into the Codex standard (Codex Alimentarius Commission, 2001). 

The ion source creates analyte ions from the neutral species in the vapor phase. Several designs of ion sources have been used for CWA degradation product analysis in recent years including thermospray ionization (TSP), atmospheric pressure chemical ionization (APCI), and electrospray ionization (ESI). These soft ionization techniques generally produce [M-H] or [M+H]" " fragments for the alkyl phosphonic acids and some other CWA degradation products. The inductively coupled plasma (ICP) is a hard ionization source and has been described in the literature. HPLC-ICP-MS has been reported for the detection of alkyl phosphonic acids.In recent years, ESI has become the most common ion source in HPLC-MS analysis in general with the APCI source a close second. The thermospray source has fallen out of favor in HPLC-MS systems since the introduction of ESI. 

COMMON STRATEGIES OF HPLC-MS IN CWA DEGRADATION PRODUCT ANALYSIS... 

Environment. Detection of environmental degradation products of nerve agents directly from the surface of plant leaves using static secondary ion mass spectrometry (sims) has been demonstrated (97). Pinacolylmethylphosphonic acid (PMPA), isopropylmethylphosphonic acid (IMPA), and ethylmethylphosphonic acid (EMPA) were spiked from aqueous samples onto philodendron leaves prior to analysis by static sims. The minimum detection limits on philodendron leaves were estimated to be between 40 and 0.4 ng/mm for PMPA and IMPA and between 40 and 4 ng/mm for EMPA. Sims analyses of IMPA adsorbed on 10 different crop leaves were also performed in order to investigate general apphcabiflty of static sims for... 

For organic toxic chemicals and their degradation products the number of possibilities is very high. The environmental samples composition usually is very complicated. Unambiguous identification needs serial-pai allel strategy of analysis with many-stage crosschecking of data. 

Tannins may be found bound up with magnetite in waterside tube deposits. Degradation products of amines, glycols, polymeric dispersants, chelants, and other organics may also be found and usually are reported in the deposit analysis as a loss on ignition. 

Figure 3.30 TIC trace obtained from the LC-MS analysis of atrazine and its degradation products. Reprinted from J. Chromatogr., A, 915, Steen, R. 1. C. A., Bobeldijk, I. and Brinkman, U. A. Th., Screening for transformation products of pesticides using tandem mass spectrometric scan modes , 129-137, Copyright (2001), with permission from Elsevier Science.

The TIC trace from the LC-MS analysis of an extracted river water sample, spiked with 3 p.g dm of atrazine and three of its degradation products, is shown in Figure 3.30. The presence of significant levels of background makes confirmation of the presence of any materials related to atrazine very difficult. The TIC traces from the constant-neutral-loss scan for 42 Da and the precursor-ion scan for m/z 68 are shown in Figure 3.31 and allow the signals from the target compounds to be located readily. 

Reliable analysis of endosulfan residue concentrations in environmental samples usually involves detection of the a- and p-isomers plus endosulfan sulfate (a degradation product of endosulfan). 

An enzyme immunoassay technique has been employed for measuring endosulfan and its degradation products (i.e., endosulfan diol, endosulfan sulfate, endosulfan ether, and endosulfan lactone) in water at 3 ppb (Chau and Terry 1972 Musial et al. 1976). However, this technique is not currently in use in environmental residue analysis. Further research into this technique could produce a rapid, rehable, and sensitive method for identifying contaminated areas posing a risk to human health. No additional methods for detecting endosulfan in environmental media appear to be necessary at this time. However, methods for the determination of endosulfan degradation products are needed. 

Analyses for the Saxitoxins. Early methods for analysis of the saxitoxins evolved from those used for toxin isolation and purification. The principal landmarks in the development of preparative separation techniques for the saxitoxins were 1) the employment of carboxylate cation exchange resins by Schantz et al. (82) 2) the use of the polyacrylamide gel Bio-Gel P2 by Buckley and by Shimizu (5,78) and 3) the development by Buckley of an effective TLC system, including a new solvent mixture and a new visualization technique (83). The solvent mixture, designated by Buckley as "E", remains the best for general resolution of the saxitoxins. The visualization method, oxidation of the saxitoxins on silica gel TLC plates to fluorescent degradation products with hydrogen peroxide and heat, is an adaptation of the Bates and Rapoport fluorescence assay for saxitoxin in solution. Curiously, while peroxide oxidation in solution provides little or no response for the N-l-hydroxy saxitoxins, peroxide spray on TLC plates is a sensitive test for all saxitoxin derivatives with the C-12 gemdiol intact. 

Therefore no trustworthy results for kinetic analysis conld be obtained from the UV-vis absorption spectra due to the formation of bixin isomers and degradation products at different rate constants. " ... 

Usually, HPLC analysis resolves four peaks identified by co-chromatography with authentic standards as copper pheophorbide a, Cn(II) chlorin e6, Cn(II) chlorin e4, Cu rhodin g7, and their degradation products, but a sum of other colored components can also be found, for example, native chlorophylls, pheophytins, pheophor-bides, and rodochlorins (free carboxyl forms of pheophorbides) besides epimers, allomers, and degradation products that have been only tentatively identified. 

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