Integration of peak areas

It IS important to remember that integration of peak areas gives relative not absolute proton counts Thus a 3 2 ratio of areas can as m the case of CH3OCH2CN correspond to a 3 2 ratio of protons But m some other compound a 3 2 ratio of areas might correspond to a 6 4 or 9 6 ratio of protons... 

Therefore, multiplicity and the relative peak heights in a multiplet provide an useful additional check on the relative number of protons obtained from the integration of peak areas. 

Automatic integration of peak areas or peak heighl measure men Is, with a choice of several calibration methods for calibration of results. 

Integration of peak areas in routine analysis is mostly achieved with electronic integrators. Two main problems arise from this evaluation technique first the definition of the baseline, and second, the determination of the time constant of the TLC-scanner and the integrator electronics. 

Peak height is not proportional to peak area. This common situation needs integration of peak area and... 

Instrumentation. Spectra were acquired with a Nicolet 60SX FTIR spectrometer, continuously purged with dry air and equipped with a liquid-nitrogen-cooled, wideband mercury-cadmium telluride detector. Coaddition of 100 interferometer scans at 8-cm 1 resolution was employed. The location of absorption maxima was confirmed by spectra taken at l-cm 1 resolution. All spectra were converted into Kubelka-Munk units prior to use. Integration of peak areas was accomplished by using software available on the Nicolet 60SX. All peak areas were normalized to the 1870-cm-1 Si-O-Si combination band (15). 

Differential nuclear Overhauser effects are either small or absent, so that integrals of peak areas can be used to calculate the relative % incorporation. 

Integration of peak areas is carried out by one of several available methods and the response compared to a calibration curve. 

In the NMR method, a deuterated chloroform solution of the polymer containing trimethylsilane internal standard is run on the proton NMR spectrometer. Integration of peak areas at delta 8 and 1-4 delta, respectively, gives a measure of signal strengths from aliphatic protons (methacrylate units) and aromatic protons (styrene). These areas can be used as a basis for calculating the methacrylate and styrene emit contents of the polymer. 

Display of chromatograms and other information in real time with high-resolution color graphics, and electronic integration of peak areas (instrumentation may include a separate computing integrator). 

NMR analyses were conducted using a Varian Unity Plus 400 Fourier Transform (FT) NMR spectrometer, which operates at 400 MHz for H observation and at 100 MHz for 13C observation. All spectra were obtained at probe temperature (22 1° C) with double precision data accumulation. Samples were provided in CDCI3, D2O or water. All samples run in CDCI3 were referenced to internal tetramethylsilane (TMS) using the CHCI3 resonance (d H, 7.24 dl c, 77.2) as a secondary reference. IH spectra in D2O and water were referenced to external sodium 3-trimethylsilylpropanoate-2,2,3,3-d4 (TSP) in D2O. Quantitative data were obtained by digital integration of peak areas. 

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