Environmental analysis compound classes

Analytical methods for parent chloroacetanilide herbicides in soil typically involve extraction of the soil with solvent, followed by solid-phase extraction (SPE), and analysis by gas chromatography/electron capture detection (GC/ECD) or gas chromatog-raphy/mass spectrometry (GC/MS). Analytical methods for parent chloroacetanilides in water are similarly based on extraction followed by GC with various detection techniques. Many of the water methods, such as the Environmental Protection Agency (EPA) official methods, are multi-residue methods that include other compound classes in addition to chloroacetanilides. While liquid-liquid partitioning was used initially to extract acetanilides from water samples, SPE using... 

Lopez-Avila V, Benedicto J, Baldin E. 1992. Analysis of classes of compounds of environmental concern III. organochlorine pesticides. J High Res Chromatog 15 319-328. 

From the selectivity point of view, LC-NMR coupling is especially suited to the analysis of compound classes such as nitroaromatics, phenols, aromatic amines, aromatic carboxylic acids, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and azo- and anthraquinone dyes. Another advantage of LC-NMR coupling for the investigation of aromatic compounds in environmental samples is that the position of substituents on the aromatic ring, e.g. in unknown metabolites or degradation products, can best be determined by NMR spectroscopy. 

Multiresidue target analysis is directed at the detection of multiple target compounds from various compound classes. In most cases, quantitative analysis as well as confirmation of identity is required. An important issue in multiresidue target analysis is the sample pretreatment, which should allow the isolation of all target compotmds, which may significantly differ in polarity, from the environmental matrix. SPE is used most often in such cases. Various MS acquisition strategies can be applied to perform this task. Some selected examples are briefly discussed below. 

Two different types of immunoassays, a competitive-type and an inhibition-type, were developed and compared for the insecticide, endosulfan. The detection range of both assay types was similar, 3-500 ng/ml for the competitive-type and 5-500 ng/ml for the inhibition-type assay. Metabolites of endosulfan and other insecticidal chloro-hydrocarbons possessing a hexachlorocyclopentene structure exhibited considerable crossreaction in both assays, so these immunoassays could be used for detection of class-specific compounds. The inhibition-type immunoassay showed less susceptibility to interfering factors and, therefore, seemed to be more suitable for environmental analysis. 

Table 7.1. Classes of Organic Compounds Commonly Encountered in Environmental Analysis of Water by Trace Enrichment SPE...

This detector can function at more than 400 °C and is not destructive since the ionization is reversible and affects only a small fraction of the molecules of each compound passing through. ECD and PID detectors are examples of class-specific detectors often used in trace environmental analysis. 

Lopez-Avila, V., J. Benedicto, E. Baldin, and W.F. Beckert. 1991. Analysis of classes of compounds of environmental concern I. nitroaromatic compounds. ]. High Resol. Chromatogr. 14 601-607. 

GC has been widely used for amine analyses because of its simplicity, high resolving power, high sensitivity, and low cost. Coupled with mass spectrometry (GC-MS), it is a technique most commonly employed for the analysis of volatile organic pollutants in environmental samples. In this combination, the GC separation usually provides isomer selectivity, while the MS shows compound class homologue specificity. The MS fragmentation pattern can provide unambiguous component identification by comparison with library spectra. 

Matrix-assisted iaser desorption/ionization (MALDI). This is another ionization method for the analysis of large molecules such as peptides, proteins, and nucleic acids, as well as some synthetic polymers. In MALDI, the analyte is first cocrystallized with an excess of a matrix, e.g., sinapinic acid or dihydroxybenzoic acid, that has a constituent aromatic component able to absorb photons from a UV laser beam. When the dried analyte matrix mixture is exposed (inside the vacuum chamber) to a sudden input of energy from a laser pulse the matrix evaporates, essentially instantaneously, carrying with it the analyte molecules. The matrix forms reagent ions that protonate the analytes. The selection of the matrix is critical as different compound classes exhibit substantial, matrix-dependent differences in ionization efficiency. The MALDI matrix should not be confused with the alternative use of the term matrix that is used to denote the medium in which biological and/or environmental components are presented, e.g., blood plasma, urine, sediment. 

Biological monitoring techniques such as immunoassays are now available for environmental analysis. These form the basis of low cost, rapid, and highly selective kits for the determination of specific compounds or classes of compounds, such as polyaromatic hydrocarbons, polychlorinated biphenyls, pesticides, herbicides, and insecticides, in food, water, and soil matrices. They are simple to use and are well suited to screening sites for contamination prior to sampling and laboratory analysis. Immunoassays can also be applied to blood and urine samples for assessing the exposure of organisms to contaminants. 

Due to their comprehensive approach, multiresidue analytical methods have become preferred tools for tracking down different compound classes at low nanogram per liter levels. They allow determination of a large number of micropollutants in a single analysis, thus reducing its time and cost. In an ideal case, a multiclass—multiresidue analytical method for determination of trace organic pollutants in environmental matrices should fulfill several criteria, such as... 

Abstract Protoberberine alkaloids and related compounds represent an important class of molecules and have attracted recent attention for their various pharmacological activities. This chapter deals with the physicochemical properties of several isoquinoline alkaloids (berberine, palmatine and coralyne) and many of their derivatives under various environmental conditions. The interaction of these compounds with polymorphic DNA structures (B-form, Z-form, H -form, protonated form, triple helical form and quadruplex form) and polymorphic RNA structures (A-form, protonated form, triple helical form and quadruplex form) reported by several research groups, employing various analytical techniques such as spectrophotometry, spectrofluorimetry, circular dichro-ism, NMR spectroscopy, viscometry as well as molecular modelling and thermodynamic analysis to elucidate their mode and mechanism of action for structure-activity relationships, are also presented. 

Tandem mass spectrometry (i.e., MS-MS) is another technique that has recently become popular for the direct analysis of individual molecular markers in complex organic mixtures [87,505,509,578 - 583]. This technique provides a rapid method for the direct analysis of specific classes of molecular markers in whole sample extracts. In this approach the system is set up to monitor the parent ions responsible for a specific daughter ion as described above and the distribution of parent ions obtained under these conditions should provide the same information as previously obtained by GC-MS [505, 582]. Even greater specificity can be achieved by a combination of GC-MS-MS [516,584]. In view of the complexity of COM samples and the need to detect the presence of individual organic compounds or classes of compounds, it would seem that MS-MS, especially coupled with GC, would be extremely valuable in future environmental organic geochemistry studies. 

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