Refractive index methods

It is essential that the solution be sufficiently dilute to behave ideally, a condition which is difficult to meet in practice. Ordinarily the dilutions required are beyond those at which the concentration gradient measurement by the refractive index method may be applied with accuracy. Corrections for nonideality are particularly difficult to introduce in a satisfactory manner owing to the fact that nonideality terms depend on the molecular weight distribution, and the molecular weight distribution (as well as the concentration) varies over the length of the cell. Largely as a consequence of this circumstance, the sedimentation equilibrium method has been far less successful in application to random-coil polymers than to the comparatively compact proteins, for which deviations from ideality are much less severe. 

Hyphenated methods can be divided into two types those that do and those that do not destroy the sample in the process of analysis. Spectrophotometric methods, thermal conductivity, and refractive index methods of detection do not destroy the sample. Chromatographic methods using flame ionization and similar detection methods destroy the sample as it is detected. Any hyphenated method that involves MS or thermal analysis (TA) will also destroy the sample. In most cases, the identification of the components in soil is most important, so the destruction of the analyte is of less importance. 

The refractive index method for the detn of wax plus lecithin described in 4.43.23 cannot be used when hot melt is present 4.4.3.5 Preparations of Solutions, Graphs and Standardization of Solutions ... 

Fig. la-f. The mutual diffusion coefficient (D22)v of dextran as a function of dextran concentration for a dextran T10 (Mw 1(f), b dextran T20 (M 2 x 1(f), c dextran T70 (Mw 7 x 10 ), d dextran FDR7783 (Mw 1.5 x 105), e dextran T500 (Mw 5 x10s), and f dextran T2000 (Mw 2x 106) 0,valuesofD22obtainedbymeasurementofthebyconcentrationgradientrelaxation as monitored by refractive index methods ( ), values of D22 obtained by photon correlation spectroscopy. Data obtained from ref. and unpublished work. For earlier studies of dextran mutual... 

In view of the great importance technically and in natural processes of adsorption in presence of water, especial attention has been directed to the detection of possible hydrogen bond interaction in aqueous media, for which the refractive index method [4] used with model compounds is useful. Table 1 summarizes some of the conclusions reached by this means, or by tests in monolayers (cf. [5]), and includes also some parallel data for interactions in non-aqueous solution. 

Detection of pilocarpine is most sensitive at its UV maximum of 215 nm. However, detection at 220 nm improves the stability of the baseline, whereas only a minor decrease - 5511 - of the peak height of pilocarpine is observed as compared with 215 nm10. The detection limit at 215 nm is about 0.04 ug, the detection limit obtained for the refractive index method is about 6 ug9. 

Sedimentation equilibrium methods measure the concentration gradients of molecules in solution when spun at high speed in a centrifuge. Samples are held in special cells in the rotor, with optically flat clear windows and, in current instruments, several samples (including controls) may be run simultaneously. The concentration gradient, as a function of radius (r), is measured using UV/visible absorbance, fluorescence or refractive index methods, using optical systems mounted outside the rotor. 

Aging Time (Days) Adsorption Isotherm Median Pore Diameter Refractive Index Method Adsorption Method... 

One of the most detailed studies on the critical micelle concentrations of betaines is that of Beckett and Woodward" who determined the CMCs of betaines with octyl to hexadecyl alkyl chains by surface tension, dye solubilization, iodine and refractive index methods. Due to the peculiar character of betaines, the conductivity method and octanol solubilizaton method were both unsuitable. 

Detection methods applied in ion chromatography (IC) can be divided into electrochemical and spectrometric methods. Electrochemical detection methods include conductometric, amperometric, and potentiometric methods, while spectroscopic methods include molecular techniques (UVA is, chemiluminescence, fluorescence, and refractive index methods), and spectroscopic techniques such as atomic absorption spectrometry (AAS), atomic emission spectrometry (AES), inductively coupled plasma-optical emission spectrometry (ICP-OES), inductively coupled plasma-mass spectrometry (ICP-MS), and mass spectrometry (MS). ... 

The ratio of 1-chlorobutane to 1-bromo-butane, 2-chlorobutane to 2-bromo-butane, or ferf-butyl chloride to tert-hutyl bromide must be determined. At your instructor s option, you may do this by one of three methods gas chromatography, refractive index, or NMR spectroscopy. The products obtained from the reactions of 1-butanol and 2-butanol, however, cannot be analyzed by the refractive index method (they... 

S.D. Raviprakash, K.S. Rai, Miscibihty studies of sodium alginate/poly(vinyl glycol) blend in water by viscosisty, ultrasonic and refractive index methods, Int J Plastic Tech, 8 334, 2004. 

Figure 9.11 Plot of the styrene peak area (Py-GC/MS) versus % bound styrene by refractive index method. Reproduced with permission from G.N. Ghebremeskel, J.K. Sekinger, J.L. Holtpanir and C. Hendrix, Rubber Chemistry and Technology, 1996, 69, 874. 1996, ACS Rubber Division [38]...

Figure 8.36 shows a calculated plot with r a=5 ander,fi=80. Curve parameter is the exponent a. Data points for sandstone (Fig. 8.33) are plotted in the curve set. The experimental data correspond with calculated curves for an exponent a = 0.35-0.70. The Complex Refractive Index Method (CRIM) curve (see Section 8.7.4.3) with the exponent a = 0.5 gives a good approximation. 

The philosophy of Wyllie s time-average formula (see Section 6.6.2) leads to the CRIM or Complex Refractive Index Method formula (Calvert et al., 1977). The time-average equation is explained as a summation of the travel time of the signal passing the solid matrix and the pore fluid both rock components are condensed as a layer. 

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