Recorder traces

The reduction of the sample was made at 2250 K In a flowing stream of hydrogen carrier gas ( SO cm /mln). The total pressure of the carrier gas was approximately 1 atm. The water vapor produced during the reduction was swept by the carrier gas Into an electrolytic-type (P2O5) moisture monitor and a continuous recorder trace of the water concentration as a function of time was obtained. A typical plot of the moisture content of the carrier gas as a function of time Is shown In Figure 3. The region on the left side of this figure where the moisture content... 

The detector noise is defined as the maximum amplitude of the combined short and long term noise, measured in millivolts, over a period of fifteen minutes. If a column 4.5 mm i.d. is employed, a flow rate of 1 ml/min is appropriate. The flow rate should be adjusted appropriately for columns of different diameters. The value for the detector noise should be obtained by constructing parallel lines embracing the maximum excursions of the recorder trace over the defined time period as shown in figure 4. The distance between the parallel lines measured in millivolts is taken as the noise level. 

Conventional UV/VIS spectrophotometer (manual measurements from strip-chart recorder traces and calculations on the basis of fitted polynomials the extraction/separation step remains). 

Figure 1.1 The first STM image of the 7x7 reconstruction of Si (111) assembled from the original recorder traces of Binnig et al. (Reproduced from Ref. 23).

The record trace [A = f(t), usually called thermogram] obtained when... 

Fig. 13.4 Recorder tracings for a mixture of five tetralkyllead compounds. Each peak... 

Schopf JW (2000) The fossil record tracing the roots of the cyanobacterial lineage. In Whitton BA, Potts M (eds) The ecology of cyanobacteria their diversity in time and space. Kluwer Academic, Netherlands, pp 13-35... 

Perhaps the most important of all electrochemical detection schemes currently in use is the electrical conductivity detector. This detector is specifically useful for ion exchange, or ion, chromatography in which the analyte is in ionic form. Such ions elute from the column and need to be detected as peaks on the recorder trace. 

Quantitation in continuous flow analysis is based on the direct comparison of the peak heights on a recorder trace of the samples and standards. It is not necessary for the reactions to go to completion, because all the measurements in a particular method are made after the same fixed reaction time, which is determined by the length of analyser tubing and relies on a constant pump speed. 

In continuous flow analysis, samples follow one another through the tubing and interaction of adjacent samples, which is called carry-over , does occur. Carry-over manifests itself on the recorder trace as peaks that are not completely differentiated. This is most noticeable when a sample of low concentration follows one of high concentration and is either seen as a shoulder on... 

The colour or fluorescence produced per mole of amino acid varies slightly for different amino acids and this must be determined for each one to be quantitated. This is done by loading a mixture of amino acids containing the same concentration of each amino acid including the chosen internal standard and from the areas of the peaks on the recorder trace calculating each response factor in the usual way (Figure 10.19). These values are noted and used in subsequent calculations of sample concentrations. 

Fig. 4.6 A typical recorder trace showing a range of standard injections in the range 0.5— 6.0 mg kg of furfural. I, injection point and t, retention time.

The 1 hour treatment at 160°C will be more severe than necessary for some samples and Inadquate for others. We have observed that storage at 160°C for as much as a day may be required to remove detectable aggregates in solutions of very high molecular weight linear polyethylene samples. In any event, the appropriate duration of such treatments can be assessed by the method discrlbed here. That is to say, the solution history should be adjusted so that direct measurements of by LALLS (without the SEC columns) yields clean recorder traces (as in Figure 1) and second vlrlal coefficients which are in accord with Kok-Rudin predictions of such values for the measured... 

Figure 2. Recorder traces of on-line SEC-LALLS experiment.

In order to obtain absolute measurements of spin concentrations, a series of standards was made up, which consisted of known weights of diphenyl-picrylhydrazyl (DDPH) diluted with potassium chloride (the mixtures were mended in a vibrating ball mill). A suitable standard was run immediately after each unknown at identical settings of instrument gain so that recorder traces of standard and unknown could be directly compared. 

All manual methods of quantifying peak size make use of the recorder tracing. Some consideration has. already been given to the peak height and width as determined by recorder chart width and chart speed. Both should be maximized for the size measurement technique used. In addition the recorder may have a limiting time constant as far as response to rapid peaks are concerned. This possibility should be considered along with the detector when time constant problems are suspected. 

The electrical signal from a detector is amplified and fed into a recorder or computer for analysis. A typical recorder trace is shown in Figure 3.5. Each peak represents a component in the original mixture. A peak is identified by a retention time, the time lapse between injection of the sample and the maximum signal from the recorder. This number is a constant for a particular compound under specified conditions of the carrier gas flow rate temperature of the injector, column, and detector and type of column. Retention time in GC analysis is analogous to the R value in thin-layer or paper chromatography. 

To set up the inhibition assay, prepare a table similar to Table E5. 1. Inhibitor should appear in the list of reagents before tyrosinase. Use the same level of tyrosinase and the same dopa stereoisomer as in part C. Vary the amount of dopa as in part C. A constant amount of inhibitor (cinnamic acid or thiourea) should be added to each cuvette. You will have to determine this level of inhibitor by trial and error. The desired inhibition rate with saturating substrate is about 50% of the uninhibited rate. Add all reagents except tyrosinase, mix well, and determine the blank rate, if any. Add tyrosinase, mix, and immediately record AA75 for 2 minutes. From recorder traces or graphs of A475 vs. time, calculate AA/min for each assay. 

If no recorder tracing is available, prepare a graph of pH vs. time for each experiment. Prepare and complete a table with the following headings ... 

Fig. 12.2 Recorder trace of Rb 52s1/2 —> 242s1/2 signal at pressures of 0.29,1.00,1.45, and 1.96 Torr of argon, with different detector sensitivities, as a function of laser detuning v. The sharp spikes are superimposed signals from a 250 MHz reference cavity (from ref. 11).

Fig. 18.2 Chart recorder trace of the 91D2-91,3G4 resonances. The resonances are power broadened by a factor of 2-3 for purposes of display. Sweep rate 0.4 MHz/s, lock-in time...

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