Solvent for the sample

Instrumentation requirements for SEC are somewhat simpler than those of other modes of HPLC, since mobile phase gradients are not used however, adequate computer support for data acquisition and processing is essential. Method development involves finding a suitable solvent for the sample and choosing a mixed bed column or, more often, a set of columns in series to match the pore size of the column(s) with the size distribution of the sample. 

A popular solvent for the sample is deuterated chloroform, CDC13. The D is the symbol for deuterium, the isotope of hydrogen that has one proton and one neutron. This solvent has no H nuclei and does not absorb RFs. It will therefore not interfere in the analysis. 

With all electron capture detectors which use tritium as the source of beta radiation, alcohols and water should be rigorously avoided as solvents for the sample and oxygen or air as a matrix for a gas sample should similarly be avoided if possible. These precautions are mentioned because each of these materials can exchange or react with the tritium in the cell resulting in decreased sensitivity or decreased detector life. 

Mobile Phases. There are few requirements the mobile liquid must meet it should (1) be a good solvent for the sample (2) have a low viscosity, like any LC solvent (3) wet the stationary phase and, if possible, help deactivate it and (4) be compatible with the detector being used. For soft gels, it must also cause the gel to swell. In general, polar liquids like water, THF, and chloroform are used. 

The apparatus used is described in Fig 1. The application of this apparatus depends on the use of a solvent which swells the latex membrane and is also a good solvent for the sample to be dialyzed. Benzene, chloroform, or methylene chloride can be used when the method is applied to coal-derived liquids. However, these solvents are not particularly effective for the dissolution of coal. On the other hand,... 

These NELC techniques can be classified into five types. Each type requires gradient elution with two or more solvents. The first type is liquid adsorption chromatography (LAC) (Table I). In LAC, initial and final mobile phases should be good solvents for the sample copolymers. Silica gel is used as the stationary phase in most cases. The sample co-... 

To classify a separation technique by LC into these two types, it should be clear whether the sample copolymers adsorb on the surface of the stationary phase or precipitate on the top of the column (phase separation) when the sample copolymers are injected into a column. If the separation mechanism is not clearly understood or when the separation by the solubility difference of the sample copolymers between the stationary and the mobile phases can be considered, then the technique can be classified into normal-phase and reversed-phase chromatography as the third type (Table III). Initial and final mobile phases should be good solvents for the sample copolymers. The initial mobile phases in Table III are 15% THF in acetonitrile (AcCN) or 10% THF in cyclohexane (J5), 35% THF in n-hexane (J6), 20% CH2CI2 in AcCN (J7), and 10% CHCI3 in n-hexane (18). The final mobile phases are 65% THF in AcCN or 60% THF in cyclohexane (15), 85% THF in n-hexane (J6), 80% CH2CI2 in AcCN (17), and 40% CHCI3 in n-hexane (J8). 

Mobile phase. The purpose of the mobile phase in SEC, is merely to act as a solvent for the sample. Hence it should be chosen to ... 

In order to utilize separation power of the layer in TLC or HPTLC, it is very important to restrict the dimension of the sample initial size, in the direction of development, to a minimum. The choice of solvent for the sample also affects the size of the sample zone. That is, we will obtain good resolution only if the development chromatographic conditions are optimally selected. For TLC plates where the desirable initial spot size is about 5.0 mm, this corresponds to a sample volume of 0.5 to 10 pL. For HPTLC plates where starting spot size is about 1.0 mm, the corresponding sample volume is 100 to 200 nL. The sample solvent must be a good solvent for the sample compounds to allow quantitative transfer from the sample application device to the thin layer. It must be of low viscosity to be easily evaporated from the thin layer. Moreover, the sample solvent must be able to wet the sorbent layer adequately to produce good penetration to... 

Which possible solvents for the sample as well as solubilities are known ... 

Good solvent for the sample to promote quantitative transfer from the sample application device to the layer... 

Approximately 5-10 % organic phase in the solvent for the sample (e.g. acetonitrile or isopropanol, or even dodecylsulfonic acid) are normally sufficient to guarantee that the solutes remain in solution and start interacting only with the right stationary phase in the column. 

If using a stronger solvent for the sample than the mobile phase eluent to dissolve the sample, care should be taken and a maximum of 5-10 p.1 should be injected. 

With 0.1 M or 0.5 M phosphoric acid solution The acid concentration can result in a different ionic strength What is the solvent for the sample (see Tip No. 13)... 

Solvent Blank Samples Solvent blank samples (pure solvent) must be injected before analysis. The same solvent is used as the dilution solvent for the samples. Dichloromethane is frequently used as solvent methanol, ethanol, and isopropanol may also be used, depending on the polarity and solubility of the sample constituents. Blank samples should also be injected during long analytical series to verify that the instrument has not been contaminated or a carryover problem exists. 

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