LC-ESI MS analysis

LC-ESI-MS analyses allowed the detection of intact flavonol glucosides (rutin) in plasma of healthy volunteers after the consumption of tomato extract [65]. 

LC/ESI-MS analyses were applied to determine urinary glucuronidated and sulfated tea catechins after the administration of green tea to humans, mouse and rats [109]. The major conjugates were identified as monoglucuronides and monosulfates of EGC and EC. Besides these metabolites, also G-methyl-EGC-G-glucuronides, O-sulfates and O-methyl-EC-O-sulfates in human urine were detected. Furthermore, the ring-fission metabolites of EGC and (-)-epicatechin, 5-(3 ,4 ,5 -trihydroxyphenyl)-y-valerolactone and 5-(3 ,4 -dihydroxyphenyl)- valerolactone respectively, have been detected in the monoglucuronide and monosulfate forms. 

Electrospray has been successful for numerous azo dyes that are not ionic salts. Several anthraquinone dyes have been analysed by LC-ESI-MS [552]. Electrospray achieves the best sensitivity for compounds that are precharged in solution (e.g. ionic species or compounds that can be (de)protonated by pH adjustment). Consequently, LC-ESI-MS has focused on ionic dyes such as sulfonated azo dyes which have eluded analysis by particle-beam or thermospray LC-MS [594,617,618]. Techniques like LC-PB-MS and GC-MS, based on gas-phase ionisation, are not suitable for nonvolatile components such as sulfonated azo dyes. LC-TSP-MS on... 

Concentrations (p.g L 1) of benzalkonium homologues in wastewater samples, analysed by on-line SPE-LC-ESI-MS under positive mode of operation (taken from Ref. [23])... 

Fig. 2.12.16. Extracted ion chromatograms (C12 homologue m z = 304, C14 homologue m/z — 332, C1B homologue mlz = 360, and Cig homologue mJz — 388) from a sediment sample extracted with ASE and analysed by SPE-LC-ESI-MS with positive ion mode of operation under full-scan conditions. Peak numbers 1 = C12BAC, 2 = C14BAC, 3 = C16BAC, 4 = C18BAC [41].

Ceglarek et al. [89] used the CW-TR fibre to analyse LAS in influent and effluent wastewater samples of a WWTP applying SPME. The optimised conditions included the addition of 0.5 g mL 1 of ammonium acetate to 3 mL of sample, extraction by immersion of the fibre (2 h) and static desorption (15 min) in isopropanol/methanol (1 1). The extracted LAS were analysed by SPME-HPLC-FD and LC-ESI-MS. The former was not suitable for quantifying LAS because of its limited extraction efficiency, whereas LC-ESI-MS showed a linear range from 0.5 to 100 xgL 1, with detection limits of 0.5 p.g L 1 for each individual homologue of LAS. The CW-TPR fibre also extracted alkylether sulfates (AESs) but not under optimised conditions. 

For quality assurance, repeatability studies need to be performed on the LC-ESI-MS by consecutive injections of the same sample. An example is shown in Fig. 4.3.6 for the analyses of four SPC homologues in a sample from a biodegradation experiment. 

In another study, samples from the Dutch coastal zone of the North Sea were collected in 1999 and 2000 and analysed by LC-ESI-MS [31]. At locations corresponding to those of the 1995/1999 studies, levels (10-30ngNPEOg 1) were observed in close agreement with the ones reported earlier. It can be concluded that, provided careful evaluation of which commercial mixture will be used as a calibrant in LC-FL, the result thus calculated can be similar to those obtained by LC-MS. 

Six sets of results from five laboratories were obtained for the analyses of NPEO in three cartridges. All laboratories used MS for quantitative analysis, except laboratory 5, which used LC-FL. Laboratory 1 used an LC with an APCI interface laboratories 2 and 4 used LC-ESI-MS and laboratory 3 used FIA-MS analysis. All laboratories performed three independent replicate analyses, i.e. analysed three replicate cartridges of each type of spike. 

However, large between-laboratory variabilities occurred that are indicative of poor reproducibility of methods. In so far as systematic trends could be observed, FIA-MS resulted more often in significantly lower concentrations than LC-MS or LC-FL methods. Within the LC-MS methods, the APCI interface yielded quantitative results which were invariably less than those obtained with LC-ESI-MS. This aspect is discussed in more detail in Chapter 4.3. LC-FL data were generally in fair-to-good agreement with LC-ESI-MS data. This held true for both LAS and NPEO analyses. 

The samples collected from the FBBR were analysed by LC—ESI—MS for the occurrence of SPC [34] (see also Chapter 2.4.4.1). The C-even-SPC were by far the most prominent intermediates (Fig. 5.1.3), whereas the C-odd-SPC were found at much lower amounts (data not shown). 

Tables 6.2.4 and 6.2.6) and particulate matter concentrations (Table 6.2.5) of NP, NPEO and NPEC were analysed by liquid chromatography electrospray mass spectrometry (LC-ESI-MS) after enrichment by solid-phase extraction (SPE) and Soxhlet followed by SPE, respectively. 

In view of the inherent resistance of some surfactant metabolite isomers to complete mineralisation, efforts have to be mounted in order to obtain further insight into the reasons behind the persistence of these, such as the SPC and nonylphenol ethoxy carboxylates (NPECs). In order to achieve this, it would thus be indispensable to be able to fully elucidate the chemical structure of individual components, e.g. after isolation from environmental samples. Through the application of, for example, LC-ESI-MS-MS in combination with NMR analyses, this is now possible. 

After the first LLE step an additional step followed potassium iodide, glycine, NaOH, and NaCl were added to the aqueous layer prior to second and third LLE with H2CC12 (1 0.7). The latter organic layers were evaporated to dryness and analysed by LC-ESI MS. 

In con (ras( to all other applications referred to in this article, that make use of 3.0-5 pm particles, Kintz et al. chose an ACQUITY C18 column (Waters) of 50 mm length and 2.1 mm I.D. packed with 1.7 pm particles. They analysed scopolamine from hair samples by LC-ESI-MS/MS with a flow of 0.3 ml/min [56], The retention time of scopolamine was as short as 1.13 min and the LOQ was excellent at 0.2 pg/ mg hair. This LOQ was 25-times lower than that obtained with conventional 3.5 pm material as reported before by the same research group (Table 8) [57],... 

Suppressing matrix effects on ionization of ipratropium (21 % suppression) were described by Ariffin and Anderson when analysing SPE extracts of whole blood by gradient RP-LC-ESI MS/MS [54], In contrast, only slight ion suppression was described by John et al. for simultaneous measuring of cocaine (4 %), homatropine (4 %), ipratropium (4 %),, S-hyoscyaminc (3 %), littorine (1 %), A-butyl-scopolamine (1 %), and scopolamine (10 %) by gradient RP-LC-ESI MS/MS [50], In this study plasma samples were precipitated with acetonitrile and the supernatant was further diluted prior to injection. 

A quite early LC-ESI MS approach was presented by He et al. in 1995 using a SQ analyser for the detection of benztropine and its biotransformation products in urine and bile after oral administration of the drug to rat [59] (Table 7). However, the lack of additional structure elucidation by mass spectrometric fragmentation restricted the analytical significance of the SQ instrument. 

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