LC coupling

In LC-LC coupling (2D system), the peak capacity is the product of the peak capacities of its component one-dimensional (ID) processes (9). The power of the separation measured by the LC-LC peak capacity is given by the following ... 

An LC-LC coupling experiment system can be performed by employing a commercially available HPLC apparatus and involving various combinations of HPLC columns, eluents, additives, switching devices and detectors. 

LC-LC coupling can be subdivided into both homomodal and heteromodal systems (11). 

LC-LC coupling systems are also employed to perform separations requiring very large plate numbers. However, it has been demonstrated (see equation (5.20) that for coupled columns peak capacity increases linearly with the square root of n... 

Specifically for triazines in water, multi-residue methods incorporating SPE and LC/MS/MS will soon be available that are capable of measuring numerous parent compounds and all their relevant degradates (including the hydroxytriazines) in one analysis. Continued increases in liquid chromatography/atmospheric pressure ionization tandem mass spectrometry (LC/API-MS/MS) sensitivity will lead to methods requiring no aqueous sample preparation at all, and portions of water samples will be injected directly into the LC column. The use of SPE and GC or LC coupled with MS and MS/MS systems will also be applied routinely to the analysis of more complex sample matrices such as soil and crop and animal tissues. However, the analyte(s) must first be removed from the sample matrix, and additional research is needed to develop more efficient extraction procedures. Increased selectivity during extraction also simplifies the sample purification requirements prior to injection. Certainly, miniaturization of all aspects of the analysis (sample extraction, purification, and instrumentation) will continue, and some of this may involve SEE, subcritical and microwave extraction, sonication, others or even combinations of these techniques for the initial isolation of the analyte(s) from the bulk of the sample matrix. 

Several methodologies have been published for the determination of selected emerging contaminants in sewage sludge. The most recently reported methods are summarized in Table 1, comprising extraction of the sludge sample, subsequent purification of the extract, and final analysis by either gas or liquid chromatography (GC or LC) coupled to mass spectrometry (MS) or tandem mass spectrometry (MS-MS). 

There are a variety of analytical methodologies developed for the analysis of emerging contaminants selected for this chapter. In almost all cases, the instrumental analysis is based on the use of GC or LC coupled to MS or MS-MS. The selection of one or another technique depends primarily on the physicochemical properties of the compounds. We summarize the more recently developed methodologies for each of the families (Table 1). 

A similar situation exists for the case of estrogens, which have also been analyzed by GC or LC coupled to MS or MS-MS. However, LC-MS offers the advantages, as compared to GC-MS, of not requiring prior compound derivatiza-tion and allowing the analysis of both free and conjugated estrogens in a single run. 

A high degree of removal efficiency of DEHP in STPs [294] has been found. Phthalates have been detected in groundwater, rivers, and drinking water [290] as well as in industrial effluents, sewage sludge, and soils [295]. Their usual analysis involves the use of both GC and LC coupled to MS detection, although sometimes a solid-phase extraction is required prior to the analysis [37,142, 296-298],... 

Seven laboratories participated in the interlaboratory evaluation within the framework of the PRISTINE, SANDRINE and INEXsPORT European Union Projects [6]. The results obtained for the analysis of diverse classes of surfactants by different analytical methods are listed in Table 4.5.1. The analytical strategies were based on LC coupled to either MS or FL detection in all cases with the exception of one laboratory using a test tube ELISA kit. Samples were spiked with the surfactants NPEO, CDEA, LAS, AEO, NPEO-SO4 and SAS. 

Eckers et al. used on-line coupled reversed-phase LC to a Q-TOF mass spectrometer, and have successfully identified trace imparities in cimetidine. In an earlier paper published by Haskins et al., they successfully identified four chromatographically unresolved reaction by-products in cimetidine, using LC-FTMS. Another example nsing fast LC coupled with a Q-TOF mass spectrometer was the identification of cimetidine-related drug substance impurities reported by Lee et al. The exact masses for six impurities were determined with an experimental error of less than 3.1 ppm. 

Separation and detection techniques for antibacterials in food mainly focus on the use of LC coupled to MS or tandem MS. Nevertheless, recent studies have suggested capillary electrophoresis coupled to laser-induced fluorescence (LIE) as a way of improving sensitivity [49], HRLC coupled to microTOF-ESI-MS as a highly selective, sensitive, and quick screening method for 100 veterinary drugs in fish, meat, and egg samples [195], and nanoscale LC coupled to UV or ion trap MS, with LODs in the range 0.01-0.51 pg/L (nanoLC-MS) and the possibility that even lower limits could be achieved by using triple quadrupole MS [59]. 

High-performance LC coupled to capillary GC is a technique in which fractions from one or more LC columns are transferred into the GC column for further separation. This coupled technique is used more to separate a particular compound and/or class of compounds from an unknown matrix. Another field in HPLC serves for the preseparation of closely related classes or subclasses of compounds (64). 

Fandino, A. S., Nagele, E., and Perkins, P. D. (2006). Automated software-guided identification of new buspirone metabolites using capillary LC coupled to ion trap and TOF mass spectrometry. J. Mass Spectrom. 41 248-255. 

Kot-Wasik, A., J. D bska, A. Wasik, et al. 2006. Determination of non-steroidal anti-inflammatory drugs in natural waters using off-line and on-line SPE followed by LC coupled with DAD-MS. Chromatographia 64 13-21. 

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