Water peak

Sample is in deionized water. Peak identification (1) (-)-epicatechin, (2) (-i-)-catechin... 

Figure 13.19 Chromatograms obtained by on-line SPE-GC-MS(SIM) of (a) 10 ml of tap water spiked with pesticides at levels of 0.1 ng 1 (b) 10 ml of a sample of unspiked tap water. Peak identification foi (a) is as follows 1, molinate 2, a-HCH 3, dimethoate 4, simazine 5, ati azine 6, y-HCH 7, S-HCH 8, heptachloi 9, ametiyn 10, prometiyn 11, fen-itrothion 12, aldrin 13, malatliion 14, endo-heptachlor 15, a-endosulfan 16, teti achlor-vinphos 17, dieldrin. Reprinted from Journal of Chromatography, A 818, E. Pocumll et al., On-line coupling of solid-phase exti action to gas cliromatography with mass specti ometiic detection to determine pesticides in water , pp. 85-93, copyright 1998, with permission from Elsevier Science.

Figure 13.20 GC-FID chromatograms of an exuact obtained by (a) SPE and, (b) lASPE of 10 ml of municipal waste water, spiked with 1 p.g 1 of seven s-triazines (c) represents a blank mn from lASPE-GC-NPD of 10 ml of EIPLC water. Peak identification is as follows 1, ati azine 2, terbuthylazine 3, sebuthylazine 4, simetiyn 5, prometiyn 6, terbutiyn 7, dipropetiyn. Reprinted from Journal of Chromatography, A 830, J. Dalliige et al, On-line coupling of immunoaffinity-based solid-phase exUaction and gas chi-omatography for the determination of 5-triazines in aqueous samples , pp. 377-386, copyright 1999, with permission from Elsevier Science.

Fig. 2.7.6 Left A representation of a Schlum- that dearly separate and correspond to the berger NMR well-logging tool [56], The long oil and water signals, respectively. The lower cylinder is the tool body and the shaded areas peak corresponds to the oil phase, the higher contain permanent magnets. The multiple peak corresponds to the water phase. Note that sensitivity regions are shown as the colored the T2 distribution of the oil and water peaks sheets that are outside the tool body. Right overlap significantly. From the map, a water...

Fig. 5.5.3 ]H NMR spectrum obtained from a sample containing catalyst and reaction mixture (i.e., methanol, acetic acid, methyl acetate and water). Peaks A and B are the intra- and inter-particle ]H resonances, respectively, associated with the OH group. Peak C is the ]H resonance of the CH30 group associated with...

This is a very polar solvent, suitable for salts and extremely polar compounds. Like DMSO it has a very high affinity for water and is almost impossible to keep dry. Its water peak is sharper and occurs more predictably at around 4.8 ppm. The residual CD2HOD signal is of similar appearance to the D6-DMSO residual signal and is observed at 3.3 ppm. 

RhCl3 in water. Peaks due to Rh, Cl, Al, O and C, due to an always present contamination by hydrocarbons, are readily assigned if one consults binding energy tables [20,21],... 

Some interesting changes are shown with potential. Broad water peaks are observed at the potential of 0.3V, and these are considerably reduced at a potential of 0.8V. However, the most interesting change is that in the potential region at more negative than 0.2, the spectrum at about 2150 is equivalent to that of the -C-0. 

We also vary the sample size (from 1 to 2 y ) between runs at a given P and T. This allows extrapolation of peak areas to zero sample size as shown in Figure 4. The flow rate within the column must be constant for an isotherm. We record the following parameters ambient pressure and temperature, inlet pressure, outlet pressure, column temperature, retention time for both air and water, water peak area, ambient flow rate, regulator pressure, sample sizes, detector current and temperature, injector temperature, and attenuation. 

Durian is one of the most commercially important fresh fruits in S.E. Asia, yet sorting immature from mature fruit by external measures is very difficult, so it is a prime candidate for non-invasive methods. Yantarasri and co-workers have sought correlations between soluble solids and sensory estimates of maturity with X-ray CT and NIRS measurements with moderate success but more recently they observed that MRI spin-echo image contrast at 0.5 T varied with the degree of maturity. Unfortunately no attempt was made to quantify relaxation time changes or separate oil-water peaks. However it was suggested that the contrast differences indicated signihcantly lower oil content in unripe durian compared to the ripe and overripe fruit. 

The ICLS model contains pure spectra of caustic, salt, water, and temperature. The conclusion of the model validation is that the ICLS model adequately describes the water peak shape changes due to caustic, salt, and temperature. Furthermore, it meets the required performance criterion for the prediction of caustic. The measures of performance are as follows (see Table 5.1 for a description of these figures of merit) ... 

This is an acceptable model performance based on the requirements of the application. The inverse model accounts for tlie eifects of salt and temperature on the water peak without explicitly using the salt or temperature infonnation in the calculations. This is in contrast to the ICLS analysis of these same data where the concentrations and temperatures of the calibration data are required to obtain a satisfactory model (Section 3.2.2.2) ... 

Note If multi-base propellants are tested using Condition A, nitroglycerin will decompose and interfere with the water peak. 

It is very difficult to achieve H NMR spectra of anthocyanins without an intense water peak around 5 ppm, which may overlap with signals commonly representing anomeric protons. After some hours of storage in the acidified deuterated solvent, this peak tends to migrate upfield -0.4 ppm. It is therefore advised to record H NMR spectra immediately after preparation to reveal peaks which may be hidden under the water peak, and to repeat this procedure after several hours as well. 

When the carrier gas of TPR was changed from He to H2, more complicated TPR spectra were obtained (Figure 21.8), because now H2 could form water and methane. The position of the water peak moved systematically to higher temperatures as the temperature of the oxygen treatment was raised. Thus, treatment temperature seems to affect not only the amount of oxygen retained in WC, but also its reactivity toward H2. However, the position of the CO peaks remained unchanged as they did in the TPR in He. 

It is apparent from Fig. 1 that the water evolution profile is qualitatively similar for water-sized and silane-treated glass fibers. Table 4 shows, however, that the desorption volume of physically adsorbed water (peak 1) is significantly larger for water-sized glass than for silane-treated specimens. This result is in qualitative accord with evidence from wetting experiments demonstrating that silane deposition diminishes the non-dispersive component of the work of adhesion with water [2-5], When bare and silane-treated fibers were equilibrated with water for 6 months, as opposed to several hours in this study, the desorption volumes of... 

Figure 15. H-NMR spectra(2C)0 MHz) of intact banana fruit tissue (A) non-MAS spectrum obtained in a conventional high resolution probe with sample axis parallel to magnetic field (B)MAS spectrum obtained without water peak suppression (C) vertical expansion of (B) (D)MAS spectrum obtained with water peak suppression, the signal-to-noise ratios (S/N) in spectra C and D are 55 and 1137, respectively. The magic angle spinning (MAS) frequency was 1.05 kHz.[Reproduced with permission from Ref.81].

Fig.4.71. Separation of some chlorophenols by cerium(IV) oxidation and fluorimetric detection. Column Corasil-C, 0.61 m X 4.83 mm I.D. Gradient elution from water to 36% acetonitrile-64% water. Peaks 1 = phenol (18.4 ppb) 2 = o-chlorophenol (22.S ppb) 3 = p-chlorophenol (20.2 ppb) 4 2,4-dichlorophenol (52.2 ppb) 5 = 2,4,6-trichlorophenol (42.6 ppb) S = solvent.

Eads, T. M. and Bryant, R. G. (1986). High-resolution proton NMR spectroscopy of milk, orange juice and apple juice with efficient suppression of water peak. J. Agric. Food Chem. 34, 834-837. 

---