Peak area integration

Maximum power heating, the L vov platform, gas stop, the smallest possible temperature step between thermal pretreatment and atomisation, peak area integration, and matrix modification have been applied in order to eliminate or at least reduce interferences in graphite furnace AAS. With Zeeman effect background correction, much better correction is achieved, making method development and trace metal determinations in samples containing high salt concentrations much simpler or even possible at all. 

TIC) acquired by GC-MS was used for peak area integration. HP MS chemstation soft-... 

The steep thermal gradient along the tube means that any variation in the sample position (e.g. because of pipetting, or spreading due to surface tension and viscosity effects) will alter the atomization peak shape. Peak area integration will help to minimize this problem, as will a rapid heating ramp and isothermal operation (see Sections 3.6.2 and 3.6.3). 

Samples and digitizes the detector signal at up to 40 Hz performs peak area integration or peak height measurement with baseline correction and deconvolution of incompletely resolved peaks. 

Evaluation of the spectral data showed that a component of the material being sprayed exhibited a significant absorption near 1480 nm (CH-bend fundamental combined with CH-stretch first overtone). This absorption was evident even after the spray had dried. Once this feature of the sprayed material was identified, it was a simple matter to apply peak area integration for the identified absorption across the entire image. The images shown on the left in the figure are maps of the peak area of the 1480 nm NIR absorption. 

Figure 4.1 Illustration of the cut-and-weigh method for peak area integration.

Anhydrotetracycline, dehydrotetracycline, and tetracycline were separated at 40°C on a Separon ODS glass-pack column (1 mm X 150 mm, 5 /urn). Mobile phase A was a 20 80 mixture of 20 mM EDTA (pH 6.4) and dimethyl-formamide. Solvent B was methanol. After 0.5 minute on solvent A, a 0.5-minute linear gradient from 0 to 50% B was started, with the higher concentration held for 2 minutes. This was followed by a return to the starting conditions with a 0.5-minute gradient. After a 1.5-minute delay, the next sample was injected. A diode-array detector was used, with peak areas integrated at 440, 400, and 360 nm for anhydrotetracycline, dehydrotetracycline, and tetracycline, respectively. 

Figure 2.7 contains plots of repetitive injection GC/MS chromatographic peak areas (integrated total ion current) as a function of sample temperature for benzene and styrene as well as selected products representing alkyl aromatics (ethyl benzene), indanes (methyl indane) and indenes (indene) evolved from PS-catalyst samples. The plots show that benzene is by far the most abundant volatile product. All of the PS-catalyst samples produce alkyl benzenes and indanes, however samples containing HZSM-5 catalyst generate significantly lower relative yields of these products. 

The area of each fjeak gives the relative number of protons and is produced directly on the spectrum (Fig. 29.6). On CW—NMR spectrometers the height of the peak area integration line must be measured using a ruler, whereas on FT-NMR machines the area is calculated and displayed as a number. You must remember that ... 

Do not expect the peak area integrations to be exact whole numbers, e.g. an area of 2.8 is probably three protons (CH3), 5.1 is probably five protons (e.g. a CpHs group), but 1.5 is probably a CH3 and all the peak area integrations must be doubled. 

Figure 2. Reversed Phase Chromatography of HPLC Peptide Standard Overlay of Before and After Microcon-SCX. Starting peptide mixture containing 45 pg in 250 pi of standard or eluted Microcon-SCX. Separation was performed by an Amicon, C18-300-10sp, (4.6 X 250 mm) using a 4 min hold at 15 % ACN, 0.25 % TFA in DIW followed by a linear gradient in 20 min from 15 % ACN to 33 % ACN at 1 ml/min. Approximately 80 % recovery of each peptide was determined by peak area integration ratios.

The measurement of peak areas radier than peak heights would undoubtedly eliminate or reduce some of the matrix effects on sensitivity reported below 13), However, the integration mode of the Perkin Elmer 503 does not provide true peak area integration, but instead provides signal averages for a preset time subsequent to initiation of the atomiza-... 

Figure 10.14. Cyclohexane spectrum following correction with Kopp 2412 glass standard. Horizontal numbers are the peak areas (integrated over the shift range indicated by the horizontal bars), relative to the 801 cm peak area. Vertical numbers are the ASTM frequencies for cyclohexane listed in Table 10.4 and Reference 11. Intensity data is average of two spectrometers calibrated independently, as described in Reference 20. (See footnote e of Table 10.7.)...

Figure 10.15. Response-corrected spectra of four common solvents obtained on a Chromex 2000 spectrometer and corrected with Kopp 2412 glass. Numbers are peak areas (integrated over the shift range shown) after normalizing to the band area indicated by LOO. (Adapted from Reference 20 with permission.)...

Processing method Controls and documents integration parameters, component names, calibration and quantitation information Integration threshold, peak width, minimum peak area, integration events Component table component names, retention times, response factors... 

Electronic peak area integration is commonplace and is utilized most often in large volume operations. It should be used if possible. It is almost always included in the software package on computer-controlled instruments. 

It is seen from figure 22.4 that the peaks are sharp and reproducible. The interpretation of the analytical result may be achieved by measuring either the peak height or the slope of the rising part of the peak, or by integrating the area under the peak. When evaluated manually peak height is the most convenient, and when computer-controlled evaluation is used peak area integration is preferred. 

It should be noted that retention-time reproducibility is not necessarily the most important parameter of an assay, but that the selectivity of a separation is more important. The influence of retention time shifts on quantitative results can be prevented by using peak area integration instead of peak-height measurements. 

The use of peak area integration instead of the peak height evaluation may eliminate kinetic interferences. 

The steps in an analysis usually include the following sampling, sample preparation and workup, separation (chromatography), detection of the analyte, data analysis including peak area integration, and calculations. With major advances in GC instrumentation and integration in the past 20 years, the major sources of GC error are usually sampling and sample preparation, especially if dirty matrices are involved. 

Figure 6.24 Schematic illustration of the difference with respect to accurate definition of a chromatographic peak between fixed acquisition times ( scan times ) as used by a linear quadrupole, and variable acquisition times dictated by automated gain control (AGC) applied in order to control space charge effects in a Paul ion trap. Since the rate of ion arrival is lower at the extremities of the peak, the acquisition times for the trap are longer than near the peak maximum, so that the start and end points for peak area integration are less well defined that in the case of fixed acquisition intervals (can be scan times or SIM/MRM channel dwell times).

Process the data and perform peak area integration for all samples. 

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