Instrumental peak broadening

The peak position and universal calibration methods rely on peak position calibration with known polymers of narrow molecular weight distribution. Several other calibration procedures requiring only a single broad moleculau weight standard have been proposed [77,439]. These procedures are quite c< plex and have a major drawback in that, unlike the peak position methods, instrumental peak broadening must be accounted for correctly if accurate results are to be obtained. 

Billiani, J., Amtmann, I., Mayr, T., and Lederer, K., Calibration of separation and instrumental peak broadening in SEC coupled with light-scattering of simple polymers,. Liq. Chromatogr., 13, 2973, 1990. 

Soares et al. [80] proposed a model using Stockmayer s distribution with additional help from a generic instrumental spreading function to account for the instrumental peak broadening in Crystaf. Again, although the model could fit the experimental profiles well, the parameters used in the spreading function were considered purely empirical. 

The peak profile analysis techniques allow separating the intrinsic and extrinsic causes producing peak broadening and shift. Accurate peak profile analysis requires the instrumental broadening well characterized and, in general, significantly smaller than the one due to sample defects (size and strain). New high quality X-ray sources and... 

Several peaks of interest (ideally higher order reflections of the same type hkl, 2h, 2k, 21, 3h, 3k, 31,. .., nh, nk, nl) are fitted by Fourier series the same procedure is applied to the diffraction lines of a reference sample, in which size and strain effects are negligible, in order to determine the instrumental line broadening. Such information is used in order to deconvolute instrumental broadening from sample effects (Stokes-Fourier deconvolution [36]). 

It is a known property of Fourier transforms that given a convolution product in the reciprocal space, it becomes a simple product of the Fourier transforms of each term in the real space. Then, as the peak broadening is due to the convolution of size and strains (and instrumental) effects, the Fourier transform A 1) of the peak profile I s) is [36] ... 

The peak broadening for the entire chromatographic system,. columns plus the instrument, may thus be estimated from the bandwidth contribution of each component of the system. The effective plate number of the system may then be calculated from Equation 1. 

In fact, peak broadening is just one of several effects observed in XRD powder patterns that can be used to gain characterization information about various catalyst systems. Particularly in zeolite systems, factors such as framework structure perturbations and modifications, extra-framework material, crystal morphology, impurities, and instrument configurations can produce observable differences in the XRD patterns, which require close scrutiny, in some cases, to understand and utilize. 

SFFF can measure gold particles down to 15 nm. Particle size distribution was determined from peak broadening caused by polydispersity of the sample. Peak broadening due to instrument imperfections was also detected. The results were compared with data from SEM and PCS. SEM gave a mean diameter of 20 nm sizing by PC was not possible due to aggregation [86]. 

Schmauch, Johnson and Stross, and Sternberg studied the influence of the detection system on peak broadening, and Glenn and Cram described a digital logic system for evaluation of instrumental contributions to peak broadening. Because... 

Care has to be taken that any connection will not introduce peak broadening Interfaces are not compatible with all the ionization modes, thus although the MS is a universal detector, the fact remains that not all compounds can be analyzed with any instrumental configuration. The price still remains much higher compared to GC-MS. 

The contribution of the channel endpieces to the peak broadening is certainly a 3D effect and should be mentioned here, although the theory used in Ref. 8 to analyze this effect was a 2D, not a 3D, one. In FFF instruments, the inlet and outlet tubes are connected with the rectangular FFF channel by triangular end-... 

It is worth noting that unlike the instrumental and wavelength dispersion functions, the broadening effects introduced by the physical state of the specimen may be of interest in materials characterization. Thus, effects of the average crystallite size (x) and microstrain (s) on Bragg peak broadening (P, in radians) can be described in the first approximation as follows ... 

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