A New Calibration Method for the Accurate Determination of Ethylene Content in Ethylene-Propylene Copolymers by CRYSTEX-IR

2012 ◽  
Vol 312 (1) ◽  
pp. 157-166 ◽  
Author(s):  
L. Romero ◽  
A. Ortín ◽  
B. Monrabal ◽  
J. R. Torres-Lapasió ◽  
M. C. García-Álvarez-Coque
Keyword(s):  
Accurate Determination ◽  
Calibration Method ◽  
Ethylene Propylene ◽  
Ethylene Content

Headspace Gas Chromatographic Estimation of Some Yogurt Volatiles

1991 ◽  
Vol 74 (4) ◽  
pp. 630-634 ◽  
Author(s):  
Franz Ulberth
Keyword(s):  
Accurate Determination ◽  
Standard Addition ◽  
Calibration Method ◽  
Relative Standard ◽  
Headspace Gas ◽  
Standard Calibration ◽  
Gas Chromatographic Method ◽  
Aroma Components ◽  
Ppm Level

Abstract A headspace gas chromatographic method Is described for the determination of acetaldehyde, ethanol, acetone, dlacetyl, and 2-butanone In yogurt. Yogurt (2 g) is equilibrated 1 h in a 10 mL vial at 60 °C, and 0.25 mL headspace gas Is splitinjected. The volatiles are baseline-separated In less than 5 min by using a thick film capillary column coated with SE-54. An external standard calibration method fulfills the requirements for an accurate determination of the yogurt aroma components. The accuracy of this method was checked by the standard addition method. The precision of the method, In terms of the relative standard deviation, depends on the analyte concentration. At the 10 ppm volatile level, RSD Is 2%, and at the 0.1 ppm level, 15%.

A Calibration Method That Simplifies and Improves Accurate Determination of Peptide Molecular Masses by MALDI-TOF MS

2002 ◽  
Vol 74 (15) ◽  
pp. 3915-3923 ◽  
Author(s):  
Johan Gobom ◽  
Martin Mueller ◽  
Volker Egelhofer ◽  
Dorothea Theiss ◽  
Hans Lehrach ◽  
...  
Keyword(s):  
Accurate Determination ◽  
Calibration Method ◽  
Maldi Tof Ms ◽  
Maldi Tof ◽  
Molecular Masses ◽  
Tof Ms

A Critical Evaluation of Infrared Methods for Determination of the E/P Ratio of Ethylene Propylene Rubbers

1966 ◽  
Vol 39 (2) ◽  
pp. 226-240 ◽  
Author(s):  
P. J. Corish ◽  
M. E. Tunnicliffe
Keyword(s):  
Block Copolymers ◽  
Critical Evaluation ◽  
Random Copolymers ◽  
Chemical Methods ◽  
Ethylene Propylene ◽  
Ethylene Content ◽  
Infrared Methods ◽  
General Method ◽  
Crystalline Polyethylene

Abstract A general method of analyzing ethylene—propylene (EP) copolymers for comonomer content is needed which is applicable to all types of copolymers: random copolymers (I), … EPEEPEPPEPEEE …; alternating copolymers (III), … EPEPEPEP …, block copolymers (II), … PEE … EEPP … PPEE … EEP …; and copolymers containing random (or alternating) segments together with blocks along the chain, i.e., mixed I or III, and II. Random copolymers can contain odd-numbered sequences of CH2 groups if the EP units are head-to-tail; if some head-to-head, tail-to-tail addition occurs, then even-numbered sequences of CH2 groups will also be present (IV; structures I—IV are shown on the next page). Block copolymers sometimes have crystalline polyethylene blocks and may also contain crystalline, isotactic polypropylene blocks. Mixed copolymers are more complex in structure than either random or block copolymers considered individually. In view of the lack of chemical methods for assessment of copolymer type or even for the determination of the propylene content of a copolymer, the most fruitful approach so far has been in the application of infrared spectroscopy. As CH2 groups in the copolymers can appear in many different environments, the method of analysis should be primarily concerned with the assay of CH3 groups. Even if appreciable head-to-head, tail-to-tail addition occurs, these methyl groups are separated by two carbon atoms, and little interaction should occur. Consideration has also been given to the measurement of ethylene content or total thickness in order to complete the basis for the calculation of the E/P ratio.

A quantitative approach to inner shell losses

1978 ◽  
Vol 36 (1) ◽  
pp. 526-527 ◽  
Author(s):  
R.D. Leapman ◽  
P. Rez ◽  
D.F. Mayers
Keyword(s):  
Energy Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Accurate Determination ◽  
Background Intensity ◽  
Core Excitation ◽  
Quantitative Basis ◽  
Cross Section Differential ◽  
Bound Electrons

Microanalysis by EELS has been developing rapidly and though the general form of the spectrum is now understood there is a need to put the technique on a more quantitative basis (1,2). Certain aspects important for microanalysis include: (i) accurate determination of the partial cross sections, σx(α,ΔE) for core excitation when scattering lies inside collection angle a and energy range ΔE above the edge, (ii) behavior of the background intensity due to excitation of less strongly bound electrons, necessary for extrapolation beneath the signal of interest, (iii) departures from the simple hydrogenic K-edge seen in L and M losses, effecting σx and complicating microanalysis. Such problems might be approached empirically but here we describe how computation can elucidate the spectrum shape.The inelastic cross section differential with respect to energy transfer E and momentum transfer q for electrons of energy E0 and velocity v can be written as

Fast calibration of CBED patterns for quantitative analysis

1993 ◽  
Vol 51 ◽  
pp. 674-675
Author(s):  
M.A. Gribelyuk ◽  
M. Rühle
Keyword(s):  
Reciprocal Lattice ◽  
Accurate Determination ◽  
Incident Beam ◽  
Crystal Thickness ◽  
Structure Model ◽  
Beam Direction ◽  
Transmitted Beam ◽  
Reciprocal Vector ◽  
On Line

A new method is suggested for the accurate determination of the incident beam direction K, crystal thickness t and the coordinates of the basic reciprocal lattice vectors V1 and V2 (Fig. 1) of the ZOLZ plans in pixels of the digitized 2-D CBED pattern. For a given structure model and some estimated values Vest and Kest of some point O in the CBED pattern a set of line scans AkBk is chosen so that all the scans are located within CBED disks.The points on line scans AkBk are conjugate to those on A0B0 since they are shifted by the reciprocal vector gk with respect to each other. As many conjugate scans are considered as CBED disks fall into the energy filtered region of the experimental pattern. Electron intensities of the transmitted beam I0 and diffracted beams Igk for all points on conjugate scans are found as a function of crystal thickness t on the basis of the full dynamical calculation.

Computer-Assisted High-Re Solution TEM

1990 ◽  
Vol 48 (1) ◽  
pp. 162-163
Author(s):  
F.A. Ponce ◽  
H. Hikashi
Keyword(s):  
Signal To Noise Ratio ◽  
Accurate Determination ◽  
Computer Software ◽  
Video Camera ◽  
Image Contrast ◽  
Objective Lens ◽  
Computer Assisted ◽  
Optical Parameters ◽  
Astigmatism Correction

The determination of the atomic positions from HRTEM micrographs is only possible if the optical parameters are known to a certain accuracy, and reliable through-focus series are available to match the experimental images with calculated images of possible atomic models. The main limitation in interpreting images at the atomic level is the knowledge of the optical parameters such as beam alignment, astigmatism correction and defocus value. Under ordinary conditions, the uncertainty in these values is sufficiently large to prevent the accurate determination of the atomic positions. Therefore, in order to achieve the resolution power of the microscope (under 0.2nm) it is necessary to take extraordinary measures. The use of on line computers has been proposed [e.g.: 2-5] and used with certain amount of success.We have built a system that can perform operations in the range of one frame stored and analyzed per second. A schematic diagram of the system is shown in figure 1. A JEOL 4000EX microscope equipped with an external computer interface is directly linked to a SUN-3 computer. All electrical parameters in the microscope can be changed via this interface by the use of a set of commands. The image is received from a video camera. A commercial image processor improves the signal-to-noise ratio by recursively averaging with a time constant, usually set at 0.25 sec. The computer software is based on a multi-window system and is entirely mouse-driven. All operations can be performed by clicking the mouse on the appropiate windows and buttons. This capability leads to extreme friendliness, ease of operation, and high operator speeds. Image analysis can be done in various ways. Here, we have measured the image contrast and used it to optimize certain parameters. The system is designed to have instant access to: (a) x- and y- alignment coils, (b) x- and y- astigmatism correction coils, and (c) objective lens current. The algorithm is shown in figure 2. Figure 3 shows an example taken from a thin CdTe crystal. The image contrast is displayed for changing objective lens current (defocus value). The display is calibrated in angstroms. Images are stored on the disk and are accessible by clicking the data points in the graph. Some of the frame-store images are displayed in Fig. 4.

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