Interface environmental analyses

On-line coupling of normal-phase liquid chromatography (NPLC) and gas chromatography is today a well developed and robust procedure and has been regularly applied to environmental analysis. When a fraction of the NPLC sample is introduced in to the GC unit, a large-volume interface (LVI) is needed but, due to the volatility of the organic solvent used in NPLC, this does not present such a great problem. 

The use of collision-induced dissociation (CID) and MS/MS techniques in conjunction with the API interfaces has dramatically impacted the fleld of environmental analysis. These techniques are now preferred for the determination of triazine compounds in water, soil, crops, etc., owing to the significant improvements in selectivity obtained via the monitoring of precursor-product ion pairs and increased sensitivity due to the reduction of chemical noise. 

R.M. Harrison and S. Raposomanikos, Environmental Analysis using Chromatography Interfaced with Atomic Spectroscopy, Ellis Horwood Series in Analytical Chemistry, Ellis Horwood Ltd., Chichester, 1992. 

The prediction that LC-MS will become a powerful tool in the detection, identification and quantification of polar compounds such as surfactants in environmental analysis as well as in industrial blends and household formulations has proven to be true. This technique is increasingly applied in substance-specific determination of surfactants performed as routine methods. From this it becomes obvious that no other analytical approach at that time was able to provide as much information about surfactants in blends and environmental samples as that obtainable with MS and MS-MS coupled with liquid insertion interfaces. 

Environmental Analysis using Chromatography Interfaced with Atomic Spectroscopy, Harrison, R.M., and Rapsomanakis, S., Ellis Horwood, Chichester, 1989. Becoming dated, but still a valuable guide to this specialist area. 

Liu, X. and J. Pawliszyn. 2005. On-site environmental analysis by membrane extraction with a sorbent interface combined with a portable gas chromatograph system. Int. J. Environ. Anal. Chem. 85 1189-1200. 

In parallel with recent developments in GC, multidimensional HPLC (LC x LC) is now also finding application in environmental analysis.33 The combination of two sufficiently different separation dimensions (e.g., NP-HPLC x RP-HPLC or IC x RP-HPLC), however, remains difficult because of the solvent compatibility issues discussed above. Here, too, HILIC may bring about a significant improvement, since its mobile phase requirements are much closer to RP-HPLC than those of other liquid chromatographic techniques.34 In contrast to GC x GC, LC x LC cannot be implemented with a (thermal) modulator that collects the analytes after the first separation dimension and reinjects them into the second column it is most practically realized with a double-loop interface that alternately collects and transfers the analytes from the first to the second dimension (Figure 13.7). Even though the second dimension chromatogram is also very fast, detection is not normally a problem since the peak widths in the second dimension are usually still of the order of 1-2 s. 

Soil and Environmental Analysis Physical Methods, Second Edition, Revised and Expanded, edited by Keith A. Smith and Chris E. Mullins The Rhizosphere Biochemistry and Organic Substances at the Soil-Plant Interface, Roberto Pinton, Zeno Varanini, and Paolo Nannipieri Woody Plants and Woody Plant Management Ecology, Safety, and Environmental Impact, Rodney W. Bovey Metals in the Environment Analysis by Biodiversity, M. N. V. Prasad Plant Pathogen Detection and Disease Diagnosis Second Edition, Revised and Expanded, P. Narayanasamy... 

In subsequent years (1988), the MAGIC system was commerciahzed, first by Hewlett-Packard (nowadays Agilent Technologies), and subsequently by other instrument manufacturers. Four commercial versions of the system have been available (1) the particle-beam interface, featuring an adjustable concentric pneumatic nebulizer, (2) the thermabeam interface with a combined pneumatic-TSP nebulizer, (3) the universal interface, in which TSP nebulization and an additional gas diffusion membrane is applied, and (4) the capillary-EI interface, which resulted from systematic modifications to existing PBI systems by Cappiello [83]. The first system was most widely used, and is discussed in more detail below. For some years, PBI was widely used for environmental analysis, especially in the US. 

The large signal enhancements often encountered with SERS have stimulated many investigations of analytical applications, examples of which are listed in Table 13.6. Many of these involve biological or environmental analysis, where low concentrations of analytes preclude the use of unenhanced or even resonance-enhanced Raman spectroscopy witout the added benefit of surface enhancement. Despite the great promise of a technique that increases Raman intensity by 10 or more, SERS has not yet resulted in widely used or routine analysis of real samples. SERS has been a very important and valuable probe of surface structure and has stimulated new discoveries about the behavior of metal-gas and metal-liquid interfaces, but its incursion into practical chemical analysis has been limited. It is worth considering why SERS has encountered formidable barriers to widespread analytical utility (2). 

Gurka DF, Titus R, Giffiths PR, et al. 1987. Evaluation of an improved single-beam gas chromatography/Fourier transform infrared interface for environmental analysis. Anal Chem 59 2362-2369. 

Harrison, R.M. Rapsomanikis, S. (eds) (1989) Environmental analysis using chromatography interfaced with atomic spectroscopy, Ellis Horwood Ltd, Chichester. 

In conclusion, the best interface and a good correlation of parameters of both the apparatus and the technique will assure the best reliability for analytical information. Automation of the apparatus not only improves the objectivity of the analysis, but is also necessary for the operator s protection. When radiochemical methods are used with automation, it is possible to obtain objective and reliable analytical information that is independent of the ambient conditions. For environmental analysis, automatic spectrometers are important to obtain continuous reliable analytical information, which is called environment monitorization. In cosmochemistry, automation of equipment and robotics is essential to assure the reliability of the information that is received by teleanalysis.218... 

Correct sampling and storage of environmental samples are indispensable in environmental analysis. On the one hand, the samples must be representative of the environmental compartment from which they were taken and, on the other hand, it must be guaranteed that the chemical composition of the samples does not change during storage. The main problem in the analysis of surfactants is that they tend to concentrate at all interfaces due to their amphiphilic nature. Consequently, losses from aqueous solutions occur because of adsorption of the surfactants to... 

The ultimate goal in environmental analysis is the quantification of individual compounds separated from all their isomers and/or homologues. Chromatographic methods like HPLC, GC, or SFC are amongst the most powerful analytical instruments with regard to separation efficiency and sensitivity. Because of the low volatility of surfactants, HPLC is used far more often than GC. Since the launch of atmospheric pressure ionization (API) interfaces, LC-MS coupling is increasingly used for determination of surfactants (Table 30.5). 

The book edited by Harrison and Rapso-manikis (1989) on environmental analysis using chromatography interfaced with atomic spectroscopy has chapters on basic principles of chromatography and AAS, interfaces between liquid chromatography and AAS and determination of individual elements. The book by Kebbekus and Mitra (1998) contains a chapter devoted to chromatographic methods, a discussion of which is also included in chapters on methods for air, water and solid sample analyses. 

R. Harrison and S. Rapsomanikis (eds.). Environmental Analysis Using Chromatography Interfaced with Atomic Spectroscospy, Ellis Horwood, Chichester, 1988, p. 189... 

The two chapters that were selected for this topic one on GC-ion trap mass spectrometry, by SabUer and Fujii and the other by Schroder on LC-MS in environmental analysis give an excellent contribution to the application of GC-MS and LC-MS to environmental analysis. Both chapters include many practical aspects and examples in the environmental field and also cover the historical perspective of the techniques and show the perspective on ionisation and scanning modes. Advances achieved in GC-ion trap by the use of external ion sources and GC/MS/MS possi-bihties are discussed. The LC-MS chapter provides an overview of the first applications of LC/MS interfacing systems, such as moving belt, direct Uquid introduction (DLI) and particle beam (PB), and then on the more recent soft ionisation techniques, like thermospray and atmospheric pressure ionisation interfacing systems. 

With a certain delay, various types of interfaces that had been developed and appHed in pharmacological and pharmaceutical research during the past three decades came to be used in environmental analytical appUcations. The following survey of LC-MS in environmental analysis" will start with a description of the moving belt interface (MBI), followed by other interface types - DLI, PBI, FAB, TSP,... 

The considerable and increasing number of appHcations where this interface operated in parallel to theTSP interface was the beginning of a fruitful development in LC-MS analysis. The method in general was reviewed in several papers and was also partly compared to results obtained by other interface types [6, 29, 32, 71]. In the field of environmental analysis, that is, predominantly in the detection, identification and quantification as weU as in the confirmation after UV-DAD [72] of pesticides, herbicides and their biochemical or physicochemical degradation products, PBI-MS was appHed. These results can be found in the Hterature together with a few results on surfactants and dyes. 

Some reviews were published dealing with this type of interface and its application in environmental analysis [24, 42, 123). Qualitative and quantitative analysis of polar pollutants by FAB or CF-FAB was performed with extracts of aqueous matrices, such as wastewater, surface water, seawater, raw and drinking water [124-129], for all types of surfactants (non-ionics, anionics, cationics and amphoterics) in urban wastewaters, receiving waters (rivers and costal receiving areas), and groundwater [124-148], for metabolites of surfactants [130, 149-153], and bromi-nated surfactants [137, 154). 

LC-MS Interfaces Applied in Environmental Analysis During the Last Decade... 

One of the most serious drawbacks that has been observed in the ionisation process with TSP, APCI, ESI interfaces, and also with FAB, is the soft ionisation of the analytes which mostly leads to molecular ions or molecular adduct ions. Though molecular mass information is provided, there is little or no structural information at all observable with PBI or electron impact (El) MS. This soft ionisation is clearly disadvantageous for any identification of environmental contaminants, since it generates either considerably less or no fragments at all, and hence is unable to confirm the presence of such compounds of environmental concern. With the commercial availability of tandem devices, tandem mass spectrometry (MS/MS) helped to overcome these identification obstacles via coUision-induced dissociation (CID) in MS/MS mode or via ion trap in MS mode. Today, even bench-top machines provide the possibility of MS . However, when TSP began to become the method of choice in environmental analysis and became commercially available, MS/MS technology was still quite expensive. Users of TSP ionisation with spectrometers not amenable for MS/MS had the possibility to record... 

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