Solution refractive index

Refractive Index is used to analyse the sample. It can also be used to help determine the percentage of a chemical (such as ethanol) in an aqueous solution. Refractive index (RI) is always reported to four decimal places. An example of the RI scale is shown in Figure 10.4. The correct reading from the RI of the sample would be 1.3764. 

The function of the detector in hplc is to monitor the mobile phase emerging from the column. The output of the detector is an electrical signal that is proportional to some property of the mobile phase and/or the solutes. Refractive index, for example, is a property of both the solutes and the mobile phase. A detector that measures such a property is called a bulk property detector. Alternatively, if the property is possessed essentially by the solute, such as absorption of uv/visible radiation or electrochemical activity, the detector is called a solute property detector. Quite a large number of devices, some of them rather complicated and tempremental, have been used as hplc detectors, but only a few have become generally useful, and we will examine five such types. Before doing this, it is helpful to have an idea of the sort of characteristics that are required of a detector. 

The sensors in this section can also be utilized to detect chemicals in liquid through the bulk solution refractive index change induced by the presence of target chemicals. Since no recognition molecules are used, this type of chemical sensing may usually have low specificity. However, these sensors may perform excellently in conjunction with other technologies such as capillary electrophoresis, mass spectrometer, and liquid chromatography in chemical detection. 

The quantity dn/dc is the specific refractive index increment and it represents the incremental change in solution refractive index with sample concentration at the wavelength, temperature, and pressure of the LALLS measurements. Since dn/dc reflects the optical characteristics of the polymer and solvent (their different optical polarizabilities), its value strongly depends on the chemical composition of both components ( 0). 

Change of the solution refractive index, n, with solute concentration, c. 

Underwood S, Mulvaney P (1994) Effect of the Solution Refractive-Index on the Color of Gold Colloids. Langmuir 10 3427-3430... 

Brix. Two methods generally are used to measure Brix or the soluble solids of citrus products. A hydrometer is used to determine the solution specific gravity and a refractometer to determine the solution refractive index (see Chapter 13). 

By expanding / so1 as a function of the dipole of the isolated molecule and the polarizability a of the molecule, it is possible to obtain an expression for ffJJP /dQ as a function of e, the solute refractive index n, the solution refractive index ns and a [17,18]. Note that the Buckingham approach accounts for nonequilibrium solvent effects (see below), described in terms of the optical dielectric constant eopt. A comparison between PCM calculated IR intensities and classical equations is reported in ref. [8],... 

Another possibility to independently measure ionic fluxes is to combine the EQCM with real time beam probe deflection technique to identify the exchanged ions [29, 30], Ionic fluxes across the electrode-electrolyte interface result in changes of the solution refraction index adjacent to the electrode surface and a transient deflection of a laser beam is measured. 

Combined measurements of the surface tension, concentration gradient, and mass transfer coefficients on the liquid-vapor interface (P < Pm) and also measurements of the solution refractive index in the vapor or liquid phase (9,1 0). 

Since the optical dielectric constant e is equal to the square of the solution refractive index, it is evident from Eq. (8.4.8) that aM may be measured by differential re-fractometry. 

Differential Scanning Calorimetry Heats of Solution Refractive Index Surface Tension Viscosity... 

X is the wavelength in vacuo, N is Avogadro s number, while A and A are the second and third virial coefficients. The term P(9 is the form factor which is a function of the size and shape of the macromolecule in solution and represents the modulation of the intensity of scattered radiation due to the finite size of the molecule and to its deviation from sphericity. The term dn/dc is the specific refractive index increment and represents the change in solution refractive index as a function of solute concentration. If experiments are conducted in the limit of zero scattering angle where P(9) = 1 as well as at sufficiently low concentrations where only the second virial coefficient need be considered, then eq. (1) reduces to... 

Underwood, S., and P. Mulvaney. 1994. Effect of the solution refractive index on the color of gold colloids. Langmuir 10, no. 10 3427-3430. 

Apparent deviations from the Beer-Lambert law arise mainly because of instrumental factors such as stray light, sample fluorescence, and use of a wide radiation bandwidth. Real deviations arise because of high concentrations which introduce solute-solute interactions and changes in s with solution refractive index, and concentration dependent chemical equilibria. 

A useful experimental method, providing quantitative information for the micelle-micelle interactions (in not too concentrated solutions), is the static light scattering (SLS). This method is based on the measurement of the concentration dependence of the scattered light and the solution refractive index [402,403]. From the intensity of the scattered light, the Rayleigh ratio, i e is determined and the data are plotted in accordance with the Debye equation [402-404]... 

Typical extinction spectra for immobilized nanoparticles of 12 nm and 39 nm diameter show that the sensor response to an increase in the solution refractive index is manifested as a red shift of the resonance wavelength and increase in the extinction (Figure 6). The change in maximum extinction (Ext" ) or extinction at 575 nm (Ext575 ,) as a function of refractive index was linear for both the 12 nm and 39 nm diameter gold nanoparticles (Figure 6). The measurement at off peak resonance wavelength was... 

---