Sample viscosity

If the samples are viscous, mixing efficiency can be affected. Incomplete mixing will result in signal changes unrelated to chemical events in the early part of 

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The detectable limits are given for samples such as they are introduced into the apparatus they should be previously diluted in order to be nebulized. It thereby is useful to apply a dilution coefficient, usually at least 10. The dilution depends on the sample viscosity. 

With several springs, which function as torque gauges, and a number of spindles, viscosities can be measured up to 10 mPa-s with the Brookfield viscometer. The shear rates depend on the model and the sensor system they are ca 0.1 100 for the disk spindles, <132 for concentric cylinders, and <1500 for the cone—plate forlow viscosity samples. Viscosities at very low (ca 10 — 1 )) shear rates can be measured with the concentric... 

Factors to be considered in maldng the selection of chromatography processing steps are cost, sample volume, protein concentration and sample viscosity, degree of purity of protein product, presence of nucleic acids, pyrogens, and proteolytic enzymes. Ease with which different types of adsorbents can be washed free from adsorbed contaminants and denatured proteins must also be considered. 

In order to achieve the best efficiency the SEC column should be operated at optimized operating parameters. The most important ones are flow rate [cf. van Deemter equation for band-broadening effects (21)], sample viscosity (depends on molar mass and concentration of the sample), and injection volume (7). 

Ideally, the sample should be injected onto the column as an infinitely thin disc, which covers the total cross section of the column. Because this is impossible, PSS has injected finite volumes onto the columns. In theory, these injection volumes should be as low as possible. In order to be able to detect the sample with significance, a certain (high) concentration of the sample has to be injected. This concept works well for low molar mass compounds, which do not generate much sample viscosity. However, when working with samples... 

With SEC retention volume calibrated against sample viscosity, the viscosity of any sample can be calculated according to equation 3, without involving MW calculations and K and a values. 

A new direct method for using size exclusion chromatography (SEC) to evaluate polymer intrinsic viscosity [n] is discussed. Sample viscosity information is obtained by combining SEC elution curve data and calibration data using direct SEC-[n] calibration procedures without involving polymer molecular weight calculations. The practical utility, convenience and the expected precision of the proposed method are illustrated. 

Czok, M., Katti, A. M., and Guiochon, G., Effect of sample viscosity in high-performance size-exclusion chromatography and its control, /. Chromatogr., 550, 705, 1991. 

Electrochemical electrodes are subject to interference from a number of substances and sampling conditions Can have a response time of 60-90 s, depending on temperature, sample viscosity and stirring speed Typical lifetime of just 3 months membranes must be changed frequently as they become fouled, damaged or clogged... 

Displacement injection is usually the preferred method because analyte ions are present in the sample zone in proportion to their concentration in the bulk sample. In addition, injection efficiency is less sensitive to variations in sample ionic strength. However, it should be noted that the presence of high salt can affect detector response and variations in the sample viscosity due to temperature, or the presence of viscosity-modifying components can affect displacement injection efficiency. 

Sample-to-sample viscosity differences Use internal standards... 

When considering liquid sampling, issues of sample path length, sample temperature and pressure, and sample viscosity, along with the overall process engineering environment, will influence the final decision... 

The high viscosity of some high MW samples is known to cause flow rate upsets as the sample passes through the SEC column frits. Such flow rate upsets often occur at the time of elution of the sample. While the flow rate upsets like this are likely to cause viscosity detection errors in most other SEC viscosity detectors, the signal of the present viscosity detector, however, will remain true, cind unaffected by the high sample viscosity problem. 

The use of discrete sample volumes to provide improved tolerance of the detector to dissolved solids, organic solvents and sample viscosity. FI provides on-line dilution and a suitable means of handling slurried samples. 

Amongst different channels of the energy dissipation, the most relevant are the sample viscosity, the contact friction, and the adhesion hysteresis. When the drive frequency is chosen to be CQ0, the power that is dissipated when the tip periodically interacts with the sample can be written as... 

Physical interferences in FLAA analysis are of the same nature as the ones in ICP-AES analysis high dissolved solids contents in samples change the sample viscosity and alter the aspiration rate. 

Supercritical fluid extraction (SFE) procedures have been developed for extractions of species of elements from samples. Viscosities and diffusion coefficients... 

There are various factors that can influence the distribution of analytes in a dried blood spot. Water-soluble chemicals uniformly coated on DBS cards would redistribute when the blood was spotted. The redistribution of chemicals may depend on their properties, viscosity of blood, the volume spotted, and the technique used for spotting. Another factor is the viscosity of the blood. Viscosity is normally dependent on the blood composition (hematocrit, protein, lipid levels), and it can affect the physical spread of the blood spot in that the same volume of a less viscous blood will form a larger diameter spot than that of a more viscous blood sample. Viscosity, combined with the chemical redistribution on the sample cards, will increase the complexity of the analyte distribution. 

Hereinafter, second values of viscosity are obtained by high-temperature polycondensation of 1,5-dihydroxyorganocyclohexasiloxanes with a,co-bis(dimethylamino)dimethylsiloxanes. For these samples, viscosities in benzene are determined. 

A better approach is the use of two capillaries (Cl and C2) in series, each of which is connected to a differential pressure transducer (DPI and DP2), and a sufficiently large holdup reservoir (H) in between. With this approach, the sample viscosity q is measured from the pressure drop across the first capillary, and the solvent viscosity q0 from the pressure drop across the second capillary. Pulsations are eliminated in this setup because they appear in both transducers simultaneously. Another design is the differential viscometer, in which four capillaries are arranged similar to a Wheatstone bridge. In Fig. 10, both designs are shown schematically. 

Figure 5-11. Influence of sample viscosity on the elution pattern of a mixture of hemoglobin (0.1%) and sodium chloride (1.0%) chromatographed on a 4x85 cm bed of Sephadex G-25 at a constant flow rate of 180 ml/hour. Dextran 2000 was added to the sample (a) at 5% final concentration (11.8 times greater viscosity than control sample) and (h) at 2.5% final concentration (4.2 times greater viscosity than control sample), (c) Control sample was not altered by addition of dextran. [From P. Flodin, J. Chromatogr., 5 103 (1961).]...

The exponent a is a measure of the interaction of the solvent and polymer. It is a function of the shape of the polymer coil in a solution, and usually has a value between 0.5 (for a randomly coiled polymer in a 0 solvent) and 0.8 (when the polymer coils expand in good solvents). The a value is 0 for spheres, about 1 for semicoils, and is between 1.8 and 2.0 for a rigid polymer chain extended to its full contour length. The proportionality constant K is characteristic of the polymer and solvent. The constants K and a are the intercept and slope, respectively, of a plot of log [ 7] versus log Af of a series of fractionated polymer samples. Viscosity average molecular weights he between those of the corresponding... 

Sample Viscosity cSt (40 °C) Color H-NMR (400 MHz) Size Exclusion RP-LC GC-FID Isomer Mix... 

Influence of sample viscosity and sampie size on microwave heating... 

For capture steps handling viscous samples or very large sample volumes. Sepharose Big Beads are for the capture step in processes where high sample viscosity precludes the use of ion exchange media with smaller bead sizes. Recommended flow velocity is up to 300 cm/h. This medium should be chosen when fast adsorption is required and resolution is of less importance. 

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