Peaks, spurious

Figure Al.1.5. Ground state wavefimetion of the double-well oseillator, as obtained in a variational ealeulation usmg eight basis funetions eentred at the origin. Note the spurious oseillatory behaviour near the origin and the loeation of the peak maxima, both of whieh are well inside the potential minima.

Fig. 7. Comparison of various transport schemes for advecting a cone-shaped puff in a rotating windfield after one complete rotation (a), the exact solution (b), obtained by an accurate numerical technique (c), the effect of numerical diffusion where the peak height of the cone has been severely tmncated and (d), where the predicted concentration field is very bumpy, showing the effects of artificial dispersion. In the case of (d), spurious waves are...

Reliable quantification is based on peak-search software that combines peak location, peak identification, and element deduction. Element deduction means that, for unambiguous detection, at least two of the principal peaks must be detected for each analyte of interest. In trace analysis, only the strongest peaks can be detected and special attention must be paid to interfering satellites and spurious peaks. 

Special solvents that are not components of the mobile phase, but are included in the sample to improve component solubility, will act as though they were solutes themselves. Each will produce a spurious peak somewhere on the chromatogram that must not be misinterpreted as a solute peak. Irrespective of the sample solvent, the solutes of interest must always be sufficiently soluble in the mobile phase to permit effective chromatographic development. 

The Auger peaks are superimposed on a large background of other scattered electrons. A CMA can filter these spurious electrons and allow the Auger electrons to reach the detector. The results are usually plotted as a derivative spectrum. 

The only problem with this method is observed for weak reflections where (+)/(-) count-rates are similar (i.e. R 1). The (+)/(-) optimised counting-time proportions must be 50%/50%, but with low count-rates, we have observed that the lack of precision may lead to proportions which are not optimum (e.g. 47%/53%). The same behaviour has been observed for peak to background proportions. In fact, when measuring a flipping ratio in many steps, we observe oscillations of the time proportions which slow the decrease of the standard deviation. Of course, these time variations have no sense, and one should calculate the variances of the optimised counting-times (Equations (16)) to avoid such spurious fluctuations ... 

Distilled or deionised water contains small amounts of organic impurities which can cause problems in long term use with bonded phase columns in the reverse phase mode. The non-polar stationary phase will collect these organics, which can alter the nature of the stationary phase or sometimes produce spurious peaks (Fig. 4.3c is an example of this). Water purification can be done by distillation from permanganate, by passage of the water through bonded phase columns, or by means of commercial systems, eg the Milli-... 

As mentioned in Chapter 3, we standardise our reporting of chemical shifts with reference to TMS or the residual solvent peak. Your spectrometer software should do this for you automatically. If it gets it wrong (which is possible if you have a mixed solvent or a spurious peak near TMS), then you can set it manually using your software. 

Up to now, in the formulation of a bolometer model, only the heat capacity of itinerant carriers was considered [57], However, our measurements show that, even at 24 mK, the presence of a spurious heat capacity in the thermometer increases the expected value of the pulse rise time. We expect that the spurious contribution in Fig. 12.17 increases down to the temperature of the Schottky peak at T = k.E/khT about 10 mK. Since gc decreases at low temperatures, the total effect on pulse rise time and pulse amplitude can be dramatic at lowest temperatures. In reality, the measured rise time of CUORICINO pulses is about three times longer than that obtained from a model which neglects the spurious heat capacity of the thermistor. For the same reason, also the pulse amplitude is by a factor two smaller than the expected value (see Section 15.3.2). 

Step functions, pulses, and square waves can be generated with a low volume, chromatographic-type 4-way valve. We have found that the desired two gas mixtures are best made up and stored in cylinders rather than made continuously by blending two streams. At the time of the switch, there is a momentary stopping of the flow, and this usually results in a change in composition if the mixture is made by the continuous blending of two streams. By this method one or more spurious peaks are added to the desired step function. Naturally these are trivial for slow responses, but important for fast ones. 

KBr methods (hardly ever called potassium bromide methods) consist of making a mixture of your solid (dry again) with IR-quality KBr. Regular KBr off the shelf is likely to contain enough nitrate, as KN03, to give spurious peaks, so don t use it. After you have opened a container of KBr, dry it and later store it in an oven, with the cap off, at about 110°C to keep the moisture out. 

The retention time results for 35 chlorinated compounds found in sewage sludge are given in Table 9.9. Not all compounds could be identified. A large number of spectra contained what appeared to be chlorine isotope clusters which are not reported. This could be due to interferences, very low levels, or spurious peaks. Although no structure... 

Attention should be paid to the appearance of spurious peaks in the fragmentation patterns of amines determined by GC-MS, when the analytes came into contact with methanol or ethanol as solvents. Thus, for example, Schiff bases may be formed on condensation of a primary amine with traces of formaldehyde or acetaldehyde present in the solvent. Although the peaks of such product may be unresolved in the chromatogram, they may appear as ions with mass increments of +12 or +26 in the mass spectrogram, complicating the identification of the analyte, as was the case with some amphetamine drugs99. 

As Figure 21 shows, even closer are the two oxidations in triferrocenylphosphate, [O = P 0(C5H4)Fe(C5H5) 3]. The small spurious peak present at about + 0.2 V in the reverse scan of the cyclic voltammogram is likely due to electrode adsorption phenomena, given the ascertained stability of the corresponding trication.34... 

A redox couple is formed as soon as the silver within the paint starts to corrode. Clearly, this can be disastrous. In addition, the silver can enter into solution if the contact is immersed in a reactive solution, again greatly complicating analytical measurements. Thirdly, the silver can be oxidized (e.g. to Ag2 0 or Ag ), thus causing spurious voltammetry peaks and removing all accuracy or chance of computing the faradaic efficiency. 

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