Peak height/area ratioing

Standardize injection volumes for more reproducible results, since change in injection volume will influence the retention time and hence peak height area ratio. If peak areas are used for quantitation instead of peak heights, changes in injection volume have little effect. 

Fig. 25. The dependence on the elapsed time of the ratios of the peak heights areas under the peaks H2/H, in the temperature regions 180-300 and 25-180, for the CaS04 Dy and CaS04 LiF, Dy phosphors.

Fig. 2. Amino acid analysis by automated ion-exchange chromatography. Standard column, 4.6 mm ID x 60 mm Ninhydrin developer. Computer print out indicates retention time (RT), height and area of peaks, and the ratio of the height of an amino acid in the sample to the height of a standard amino acid.

Based on the analytical figures of merit of the methods in Table 1, the best precision and selectivity are accomplished by using the decay rate rather than the formation rate or conventional CL-measured parameters such as the peak height or area under the CL curve. Table 2 gives the selectivity factor, expressed as decay-rate and peak-height tolerated concentration ratio, for the CL determination of hydrogen peroxide using SF-CLS. As can be seen, the selectivity factor was quite favorable in most instances. 

Compound 22 can be conveniently prepared in multigram quantities and has been found to be useful for assessing the enantiomeric purity of 1,2-glycols. Because the ketal carbon represents a new chiral center, the formation of four diastereomers is possible. However, the diastereomeric pair 23a and 23b (or 23c and 23d) shows 1 1 peak height in 13C NMR or equal peak areas in HPLC the diastereomer composition measured by the ratio of 23a to 23b or 23c to 23d reflects the enantiomer composition of the original 1,2-glycol. 

IS. Peak-area or peak-height ratios are calculated for the analyte and IS and plotted against the ratios of known concentration of the analyte and IS. 

Figure 2.12 Ratio of peak area and height related to time constant of detector. Experimental conditions are the same as those in Figure 2.11. Peak height and area ratios are calculated from the data of peak nos. 1 and 4 as a %> of the maximum value. Lines A, peak height ratio of chromatograms measured at...

Studied responses were resolution, " " analysis time, migration time, plate count, tailing factor, tablet content, peak area, peak height, peak width, and peak area/migration time ratio. ... 

Quantitation by Internal Standard. Quantitation by internal standard provides the highest precision because uncertainties introduced by sample injection are avoided. In this quantitation technique, a known quantity of internal standard is introduced into each sample and standard solutions. As in the external standard quantitation, chromatograms of the standard and sample solutions are integrated to determine peak heights or peak areas. The ratio of the peak height or area of the analyte to an internal standard is determined. The ratios of the standards... 

Figure 5.1 shows a portion of a chromatogram. Three parameters are illustrated, the peak width, W, the noise, N, and the peak height, S. Peak height is measured in any convenient units from the base of the peak to its maximum. The width of the peak (in seconds) is defined in various ways (a) the peak width at half the height (illustrated), (b) the base of the triangle which most closely matches the shape of the peak, (c) a multiple of the variance, or second moment, of the peak shape, (d) the ratio (in consistent units) 2A/S where A is the area of the peak. The first method is used here because it is the easiest to measure. 

A response factor is a ratio of signal-to-sample size. There are two kinds of response factors. Some response factors are numbers used in calculating the quantities required in a chemical analysis. They can be in any convenient form, including the inverse, that is, sample size divided by signal. They may, if desired, involve an internal standard, take account of efficiency of sample workup, or be expressed in arbitrary units. The response factors considered here, however, are meant to characterize detectors. They should be independent of carrier flow, Fc and the units of sample size should reflect the way the detector works. For any particular detector, there are two ways to define response factor, depending on whether peak height, S, and peak width W, are measured, or whether an integrator makes areas. A, available. They can be shown to be equivalent to the extent that SW/2 = A. 

QUANTITATIVE ASPECTS. Peak areas are generally used (area = height x width at half-height). The peak area ratio sample to internal standard was plotted against the corresponding weight of serial amounts of standard compound. A standard curve must be obtained for each individual acid because of differences in detector response. 

With the Chromalytics Model MC-2 mass chromatograph, a sample is introduced into the unit, split into two portions, collected onto traps, and then analyzed simultaneously with two gas density detectors as shown in Figure 1. The peak height or area ratios from each detector are measured and the molecular weights calculated from Equation 3. 

In actual operation, the molecular weight of an unknown can be determined by measuring the area or peak height ratio and using a K established for known compounds. Fortunately, it is not necessary to know the amount of sample introduced. For either molecular weight or... 

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