Chart recorders peak area

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. 

To measure k using the online detector, the packed columns were replaced by a length of l/l6 in OD ss tubing and peak areas corresponding to injections of various particle suspensions and sodium dichromate solutions were recorded on chart paper. The following analysis was then applied. 

Go back and read about HPLC peak interpretation in the section on GC peak interpretation ( Sample on the Chart Recorder ). The analysis is exactly the same, retention times, peak areas, baselines,... all that. 

The amount of each FAME present is proportional to the area under its peak on the recorder chart. If the peaks are symmetrical, the peak area may be calculated by triangulation ... 

Usually the amino acid analyzer is first standardized by running through it a sample containing known quantities of amino acids to account for any differences in their ninhydrin reaction properties. In this way it is possible to relate directly the amount of amino acid present to the amount of colored product formed, as measured by the area under the peak produced on the strip-chart recorder (see fig. 3.15). Similarly, the amino acid hydrolysate of a protein of unknown composition can be run through the analyzer, and the relative peak areas can be used to estimate the ratios of the different amino acids present. 

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 basic components of an HPLC system are (1) a pump with a constant flow control (2) a high-pressure injection valve (3) a chromatographic column (4) a detector and (5) a strip-chart recorder or a data system for measuring peak areas and retention times. Calibration standards are prepared at various concentrations and the retention times and peak areas of the analytes are compared against the standard solutions of analytes for their identifications and quantitations. 

It should be noted that meal indicates the quantity of heat determined from the peak area on a recording chart... 

The area under any peak on the chart recorder is proportional to the quantity of that component and the method is therefore quantitative. 

A gas chromatograph (GC) is a device used to separate the components of a sample of a gas or liquid mixture and to provide a measure of the amount of each component in the sample. The output from a chromatographic analysis typically takes the form of a series of peaks on a strip-chart recorder. (See the preceding problem.) Each peak corresponds to a specific component, and the area under the peak is proportional to the amount of that component in the sample [n,(niol) = k,A, where A, is the area of the peak corresponding to the ith species]. The proportionality constants k,) are determined in separate calibration experiments in which known amounts of the components are injected into the GC sample port and the corresponding peak areas are measured. 

Typical Response Peaks. Figure 2 shows some typical response peaks for the HPLC separation of the saturates and aromatics in a typical vacuum gas oil. The curve in the upper portion of the figure is the response for the sample using the RI detector. After the saturates peak appeared, the backflush valve was switched and the attenuation changed as indicated in the figure. The peaks were very sharp and symmetrical and appeared in less than 10-min lapsed time from the point of injection. Base line drift was minimal and the areas of the response peaks were obtained with a ball and disc integrator on the strip chart recorder. 

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 samples were analysed for total volatile sulphur gases and the results for the surface microlayer are presented in Figs. 8-18 to 8-20. The data are presented as peak areas from the strip-chart recorder of the analytical unit, as calibration of the response of a pulse of gas containing varying proportions of different species is not possible. On traverse A-A it is clear that there is a distinct pattern of three zones of higher sulphur values. There is a discontinuous series of anomalous values at the southwestern end of the traverse, which begin over the suboutcrop of Zone I and extend into the area underlain by the downdip extension of the mineralisation to a point where the depth to mineralisation is of the order of 80-90 m. This is followed by a series of generally low values until the samples are... 

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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