ESI-MS analysis

Fig-1 SPE-LC-ESI-MS analysis (SIM mode) of two wastewater samples, spiked at different levels of concentration. Compounds (1) ciromazine, (2) oxamil, (3) metomil, (4) carbendazime, (5) thiabendazole, (6) imidacloprid, (7) acetamiprid, (8) thiacloprid... 

Pressurized sample infusion An easily calibrated, low volume pumping system for ESI-MS analysis of reactions... 

Fig. 2.6.1. RP-LC-ESI-MS analysis of flocculation sludge from a Barcelona drinking water treatment plant. Column Cig LiChrolute 250 X 4.6 mm, 5 pm, gradient elution with ACN-water. Upper trace total ion current (TIC), lower traces extracted ion chromatograms for NPEOs, raE0 = 1-5. Inset ESI mass spectrum of NPEO oligomeric mixture.

Determination of two esterquats used as substitution products of DTDMAC, such as diethylester dimethylammonium chloride (DEED-MAC) and diesterquaternary (DEQ) (Fig. 4.2.8) in sewage water samples was carried out by the same ion-pair extraction procedure for the analysis of DTDMAC reported elsewhere [103,111] followed by microbore HPLC-ESI-MS analysis [116] and quantification employing commercial blends. 

Shang et al. [7] studied the effect of different additives (NaAc, NaOH, NaCl, NH4Ac) on analyte signal intensity and they found that the relative intensity of NPEO adduct ions may be enhanced by all additives, but NaAc produced the most abundant adduct ions for the entire ethoxylate series with good reproducibility. Additionally, the intensity of adducts, especially for mono- and diethoxylates was found to depend on reaction time prior to LC-ESI-MS analysis and concentration of NaAc. They recommended 0.5 mM NaAc for normal-phase separation with solvent system toluene-MeOH-water. In reversed-phase systems the highest abundance of sodium adducts for NPEOs ( iEO = 1-10) was observed at concentrations higher than 10 xM, while any further increase in concentration had very low influence on signal intensity [10,11],... 

A further successful attempt to detect a,(3-unsaturated SPC (SPC-2H) during the degradation of LAS was achieved by Eichhorn and Knepper [34] (Fig. 5.1.8). An SPC-2H has m/z of two mass units below that of the corresponding SPC, and compounds of this type have been described in the degradation of impurities in LAS, the monocarboxylated DATS [88,104]. However, a definite distinction between the known DATS carboxylates [88] and the putative SPC-2H could be provided by LC-ESI-MS analysis, which enabled structural assignment via... 

Fig. 3.82. LC/ESI-MS analysis of reacted RB4 (500 mg/1) in negative ion mode of operation total LC chromatogram (a) and enlarged chromatogram from 25 to 30 min retention time (b). Reprinted with permission from W. J. Epolito et al. [145],...

Differently from serine, ESI-MS analysis of homoserine (HSer) solutions reveals an unusually abundant diprotonated homoserine octamers [(HSer)g-2H], but not the expected monoprotonated [(HSer)g H]" one." A 3/1 mixture of L-serine and L-homoserine yields abundant mixed serine octamers with the incorporation of one or two homoserine molecules into the cluster. CID of the isolated [(Ser)6(HSer)2-H] cluster leads to the preferentially loss of two neutral serine molecules. Homoserine is always retained. The ESl-MS spectral patterns of threonine and allothreonine solutions is similar to that of homoserine. A 1/1 mixture of D-serine and D-threonine yields abundant mixed singly- and doubly-charged octamers incorporating from 2 to 6 threonine molecules. Their relative abundance indicates that threonine may incorporate freely into serine clusters because the additional methyl group does not interfere with the bonding of the cluster. 

Enzymes, enantoselectivity, 148 Equilibrium chemical isotope effects, 28 for NCMH model, 40-41 ESI-MS analysis... 

FIGURE 3 CE-ESI/MS analysis of a stressed galantamine sample (18 months, 25°C, 60% relative humidity) with structures and MS/MS spectra of both identified degradation products (peaks I and 2, m/z 302 and 274, respectively). Adapted from reference 169 with permission from Wiley-VCH Verlag GmbH. 

FIGURE 4 Chiral CE ESI/MS analysis of five amphetamine derivatives and two pharmaceutical compounds. Total ion current (TIC) and extracted ion currents (XIC) of amphetamine (A), methamphetamine (MA), methylenedioxyamphetamine (MDA), methylenedioxymethamphetamine (MDMA), and methylenedioxyethylamphetamine (MDEA), and tramadol (TMD) and methadone (MTD) in plasma after LLE with electrokinetic injection. 

FIGURE 5 Chiral CEC-ESI/MS analysis of eight /l-blockers 1,1 = oxprenolol, 2,2 = alprenolol, 3,3 = pindolol, 4,4 = metoprolol, 5,5 = propranolol, 6,6 = talinolol, 7,7 = atenolol, 8,8 = carteolol. Reprinted from reference 288 with permission from Wiley-VCH Verlag GmbH. 

Cheynier V, Doco T, Fulcrand H et al (1997) ESI-MS analysis of polyphenolic oligomers and polymers. Analysis 25 32-37... 

Choung M, Baek 1-Y, Kang S-T et al (2001) Isolation and determination of anthocyanins in seed coats of black soybean (Glycine max (L.) Merr.). J Agric Food Chem 49 5848-5851 Lee JH, Kang NS, Shin S-O et al (2009) Characterization of anthocyanins in the black soybean (Glycine max L.) by HPLC-DAD-ESI/MS analysis. Food Chem 112 226-231 Springob K, Nakajima 1, Yamazaki M et al (2003) Recent advances in the biosynthesis and accumulation of anthocyanins. Nat Prod Rep 20 288-303... 

Direct and Indirect ESI-MS Analysis of Non-covalent Drug-Protein Complexes... 

Protocol 2.11 Automated desalting protocol for ESI-MS analysis of intact proteins... 

Because of the combined effects from EOF and chromatographic interaction, the content of the organic solvent in the buffer is often higher than that used in RPC separation of peptides. This feature facilitates resolution of hydrophobic peptides, whilst at the same time permitting the fractions to be presented in a state compatible for direct ESI-MS analysis. 

In this way, the reaction mixtures for the synthesis of the 24-26 clusters have been subjected to negative-ion ESI MS analysis and several negatively charged intermediates have been detected. Some identified species were cluster anions [C36H8oLi308Zn2] = [(Me2ZnOBu-f)2 + Li + (LiOBu-t)2 + 4THF] (for compound... 

The combination of top-down and bottom-up strategies on the salivary characterization presents the advantages of each one and relied on the identification of more than 2000 different peptides (5,27,35-37,40—42). From those, only about 30-40% identified peptides belong to the major salivary peptide classes referred in the preceding text, the remnant peptides originating from sources such as plasma, squamous cells, and crevicular fluid. Peptides of major classes are usually detected by LC-MS analysis, independently of intra- and interindividual variability. Indeed, a repertoire of 233 masses belonging to these naturally occurring peptides has been consistently detected by LC-ESI-MS analysis of the salivary peptidome (43). 

A microchip was constructed to sequentially load and inject samples from a 96-well plate for ESI-MS analysis. As shown in Figure 4.21, a sampling capillary is inserted in the guide tube (P) on the left side by applying a vacuum at the... 

Desalting of samples was also carried out before ESI-MS analysis. To achieve this, a PVDF membrane was sandwiched at the sample reservoir on a chip for... 

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