Overview spectrum

The FIA-MS screening approach using soft ionisation interfaces prior to any CID procedure provides an overview of the MS separation procedure, which is based on the different m/z ratios of the molecular or cluster ions generated. With the help of this very fast screening method—positive or negative FIA-MS by-passing the analytical column—the surfactant chemist is able to characterise complex blends and formulations without difficulty (Fig. 2.5.1) while the experienced analyst is able to make initial statements about the presence of frequently used and therefore most important surfactants in environmental samples (Fig. 2.5.2) despite the presence of complex matrices. The information provided by ESI or APCI—FIA—MS overview spectra for a first characterisation [8,17-19], which were also available with non-API soft ionising interfaces such as FAB [20] or TSI [9] in industrial blends as well as environmental samples, were obtained from ... 

As an example of an anionic surfactant mixture frequently contained in detergent formulations, an AES blend with the general formula C H2 i i—O—(CH2—CH2—O) —SO3 was examined in the negative FLAMS mode. Because of the considerable differences observed between both API ionisation mode overview spectra, the ESI—FIA—MS(—) and the APCI—FIA—MS(—) spectra are reproduced in Fig. 2.5.3(a) and (b), respectively. Ionisation of this blend in the positive APCI—FIA—MS mode, not presented here, leads to the destruction of the AES molecules by scission of the O—SO3 bond. Instead of the ions of the anionic surfactant mixture of AES, ions of AE can then be observed imaging the presence of non-ionic surfactants of AE type. 

Fig. 2.5.10. (a) APCI-FIA-MS(+), (b) ESI-FIA-MS(+), (c) APCI-FIA-MS(-) and (d) ESI-FIA-MS(—) overview spectra all recorded from the methanolic solution of the same commercially available household detergent mixture containing different types of... 

Fig. 2.5.12. APCI-FIA-MS(+) overview spectra of industrial surfactant blends used as pure blends or mixtures in the examination of ionisation interferences, (a) C13-AE, (b) cationic (alkyl benzyl dimethyl ammonium quat) surfactant, (c) amphoteric C12-alkylamido betaine, and (d) non-ionic FADA all recorded from methanolic solutions. 

In the qualitative analyses of surfactants, the FIA-MS screening method applying both soft ionising API interface types, APCI and ESI, provides the overview spectra that contain the molecular ions or adduct... 

Fig. 2.9.7. (a) ESI-FIA-MS(+) and (b) APCI-FIA-MS(+) overview spectra of synthetically produced mixture of di-carboxylated PEG homologues (f) APCI-LC-MS(+) and (j) APCI-LC-MS(-) RICs of mixture as in (a,b) (c-e) selected mass traces of di-carboxylated PEG homologues under positive and (g-i) negative ionisation. Gradient elution separated by RP-Ci8 column [24]. 

Fig. 2.9.10. Interdependences of temperature and ions examined in the APCI-FIA-MS(+) process. Overview spectra of AP blend ionised at source temperatures ((a) 400°C and (b) 200°C) resulting in [M + NH4]+ and [M + H]+ ions and [M + NH4P ions of PPG...

Fig. 2.9.44. ESI-FIA-MS(+) overview spectra of partly fluorinated non-ionic surfactant blend with the general formula C F2n+1-(CH2-CH2-0)m-H identical with CnF2n+1-CH CHa-O-CCHa-Cttj-O -j-H [16],... 

The qualitative determination of anionic surfactants in environmental samples such as water extracts by flow injection analysis coupled with MS (FIA-MS) applying a screening approach in the negative ionisation mode sometimes may be very effective. Using atmospheric pressure chemical ionisation (APCI) and electrospray ionisation (ESI), coupled with FIA or LC in combination with MS, anionic surfactants are either predominantly or sometimes exclusively ionised in the negative mode. Therefore, overview spectra obtained by FIA—MS(—) often are very clear and free from disturbing matrix components that are ionisable only in the positive mode. However, the advantage of clear... 

FIA-MS overview spectra in the APCI(-) and ESI(—) mode proved that the AES blend examined, contained two mixtures of homologues with Ci2 and C14 alkyl chains (Fig. 2.11.7(a)). FIA-MS(—) spectra confirmed that, in addition to AES compounds, the ASs precursor compounds with n = 12 and 14 and x = 0 (mJz 265 and 293) were also present. In the AES molecules, the Ci2 and C14 alkyl chains were coupled with ethoxy chains that could be ionised to a quite different extent. While APCI(—) ionised AESs up to 14 or 9 polyglycol ether units for the Ci2 and C14 homologues, respectively, ESI(—) ionised AESs up to 6 or 4 PEG units, all equally spaced by Am/z 44 (cf. Table 2.11.1). 

For comparison of the different ionisation methods and detection modes, the results obtained as FIA overview spectra are presented in Figs. 2.11.7 and 2.11.8. Reconstructed ion chromatograms (RIC) of APCI and ESI combined with selected mass traces of all LC separations and, in parallel, the selected standardised mass traces of the C42 and C14 homologues containing three ethoxy chain links recorded in the negative mode are presented in Fig. 2.11.9. These results again demonstrate the quite large variation in the ionisation efficiency of... 

Fig. 2.11.16. APCI-FIA-MS(-) overview spectra of di-NPEC (C9Hi9)2-C6H3-0-(CH2-CII2-0)x-CH2-C02 H+) blend [22,61],...

Fig. 2.12.11. FIA-ESI-MS(+) overview spectra of (a) SFE extract of wastewater sludge and (b) of an industrial blend of quats. Reproduced with permission from Ref. [22] 1996 by American Chemical Society. 

Fig. 15.1. a-c Overview spectra of non-ionic polyethylene glycol (PEG) surfactant mixture (AEOs with general formula C H2 +]0-(CH2-CH2-0),-H (n = 13 x= 1-17)) recorded in flow injection mode (FIA) bypassing the analytical... 

Fig. 4.10 MIE spectra with 1 Oi/SA, 2 CO/SA as well as 1 Oi/SA with 1CO/SA before and after TPR reaction to 180 K on Pt (111). Overview spectra (a) including the CO spectra from the previous section for comparison in excerpt (b) the spectral features are assigned to MOs, for details see text...

From the numerous fine-sfiuctured PO bands the authors selected five PO lines at 246.40 nm, 247.62 nm, 247.78 nm, 324.62 nm and 327.04 nm, respectively, which were all band heads with a FWHM of less than 20 pm. The relative sensitivity of the five lines is compiled in Table 6.20, and the band head at 246.40 nm is the most sensitive, although the difference in sensitivity is not very great. Nevertheless, as can be seen from the enlarged overview spectra in Figure 6.8, the band head at 324.62 nm should be the line of choice because the spectral environment is much simpler. However, any of the other lines may be chosen in the case of any spectral interference, which has been carefully investigated by the authors. 

Figure 7.2 Overview spectra recorded with the ARES spectrograph (a) deuterium lamp without flame (b) deuterium lamp with air/ acetylene flame (c) resulting calculated flame transmittance...

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