Chart recorders peak height

The mixture is identical in each example. The peaks are shown separated by 2, 3, 4, 5 and 6 (a) and it is clear that a separation of 6a would appear to be ideal for accurate quantitative results. Such a resolution, however, will often require very high efficiencies which will be accompanied by very long analysis times. Furthermore, a separation of 6o is not necessary for accurate quantitative analysis. Even with manual measurements made directly on the chromatogram from a strip chart recorder, accurate quantitative results can be obtained with a separation of only 4a. That is to say that duplicate measurements of peak area or peak height should not differ by more than 2%. (A separation of 4a means that the distance between the maxima of the two peaks is equal to twice the peak widths). If the chromatographic data is acquired and processed by a computer, then with modem software, a separation of 4a is quite adequate. 

Perfluoroalkane-225 (PGR, Gainesville, FL) was admitted through a glass inlet system to provide reference peaks. Analytical and reference peaks for the nitrosamines studied are shown in Table I. Sample and reference peaks were scanned alternately at a repetition rate of approximately 1 sec and were monitored on an oscilloscope. When the nitrosamine peak appeared, the oscillographic recorder chart drive was engaged and remained on until the peak disappeared. Nitrosamine quantities were estimated by comparing the sum of sample peak heights measured from the chart (usually 10 to 20 values) with values derived from injection of standard solutions. 

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. 

When Fab-B(SH) has been eluted, connect a second, larger Sephadex G25 column (2 6-cm diameter, bed height 20 cm) to the chart recorder. After the 30 min-mcubation, load the Fab-A(SH)/o-PDM/DMF mixture onto this second G25 column, and elute at a flow rate of approx 200 mL/h. Collect the Fab-A(mal) protein peak (elutes after 8-10 min), taking a 45-pL sample for HPLC analysis Stop collecting when the chart recorder pen has returned half way to baseline to avoid contamination with o-PDM/DMF, which elutes as a large second peak... 

Strip-chart recorders are still the least expensive option, but areas and retention times have to be manually calculated from the tracing. The more expensive integrators, using small memories, give us a time-noted trace followed by a report of areas (or peak heights) versus retention times. The computer requires much more memory to store the one point per second (or more) required for an HPLC run. However, it has much more flexibility in manipulation, redisplay, calculation, and report generation. Data processing will be covered in detail in Chapter 14. 

The normal procedure for the use of the ion chromatograph was followed, with the exception of the use of the electrochemical detector after the anion suppressor. The solutions were injected and the detector and chart recorder were adjusted to provide peaks of appropriate height. 

Detect the PTC-amino acids as they elute with a spectrophotometer set at 254 nm. When the signal output (10 mV maximum) is relayed to a chart recorder with a speed of 0.5 cm/min, the PTC-amino acid peaks will show good height and good resolution. 

Output of the detector may be recorded by a strip-chart recorder or by an integrator. Strip-chart recorders are difficult to work with when analysing mixtures of compounds because of the need to manually change attenuation and record retention times whilst compounds of different concentrations are rapidly eluted. Peak heights or areas must also be measured or computed manually. 

The determination of Dp involves the measurement of H at several relatively high flow rates, where the term B/u is negligible. The slope obtained in a plot of H versus u enables one to calculate Dp, since K is known in these experiments. The plate height, H, is determined from the eluted peaks displayed on a chart recorder by... 

Ion Chromatograph. A Dionex Model 14 was used for the determination of anions. The working parameters are given elsewhere (12). Quantification was done by comparing the peak heights on the strip-chart recorder of the standards with the sample solutions. 

If peaks are symmetrical, as is frequently the case with modern capillary columns, only the peak height must be converted. When recording the chromatograms on a strip chart recorder, the chart speed on the recorder should be increased to obtain an accurate measurement of the peak width. The area can then be obtained by triangulation. Other required data are the flow rate through the detector and the moles of sample in the detector. For samples that are split the measurement of the split ratio is also required to obtain the number of moles injected. The... 

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