## What is the role of mobile and stationary phase in chromatography?

Chromatography is a method by which a mixture is separated by distributing its components between two phases. The stationary phase remains fixed in place while the mobile phase carries the components of the mixture through the medium being used.

## What are mobile and stationary phases in a chromatogram?

In thin-layer chromatography (TLC), the stationary phase is a thin layer of solid material, usually silica-based, and the mobile phase is a liquid in which the mixture of interest is dissolved.

What is mobile phase in chromatography?

The mobile phase is part of gas chromatography mass spectrometery testing. It is an an inert gas that the sample is injected into that will carry it through the stationary phase, it moves the sample so that it is mobile.

In which chromatography stationary phase is more polar than mobile phase?

normal phase chromatography

The chromatography in which the stationary phase is more polar than the mobile phase is called normal phase chromatography. Whereas, if the stationary phase is non-polar, and the mobile phase is polar, then this chromatography is reverse phase chromatography.

### Is mobile phase polar or nonpolar?

Principle. In normal-phase chromatography, the stationary phase is polar and the mobile phase is nonpolar.

### Is stationary phase polar or nonpolar?

Stationary phases are usually very polar, while mobile phases vary widely in polarity, but are less polar than the stationary phase. This is called normal phase (NP) chromatography.

Is the stationary phase polar or nonpolar?

Why do we use Rf values?

In chromatography, Rf values are the most basic prerequisite of the experiment. These numbers indicate whether the analyte (solute) prefers the stationary or mobile phase. With stationary and mobile phases, Rf values are used to determine polarity, relative masses, and relative solubilities, among other things.

#### What is the formula for Rf value?

The Rf value of a compound is equal to the distance traveled by the compound divided by the distance traveled by the solvent front (both measured from the origin).

#### What is Rf value?

The Rf (retardation factor) value is the ratio of the solute’s distance travelled to the solvent’s distance travelled. The word comes from chromatography when it was discovered that a given component will always travel the same distance in a given solvent under the same conditions.

Why GC columns are longer than HPLC?

A gas encounters less resistance in the GC column which permits use of longer column lengths. Sample stability – samples analysed by HPLC are generally thermally labile so they are in liquid phase in the HPLC column at room temperatures.

Why is Rf less than 1?

By definition, Rf values are always less than 1. An Rf value of 1 or too close to it means that the spot and the solvent front travel close together and is therefore unreliable. This happens when the eluting solvent is too polar for the sample.

## What is the unit of Rf value?

Rf values do not have units since it is a ration of distances. Because mixture solvents are often applied Rf values are usually written as the following examples: Rf = 0.66 (60% Ethanol) – if % is given it is assumed that the mixture is in water hence 60% ethanol 40% water.

## Is silica gel polar?

Silica gel is a polar adsorbent. This allows it to preferentially adsorb other polar materials. When it comes to polarity, materials interact more with like materials. This principle is particularly important to many laboratories, which use silica gel as the stationary phase for column chromatography separations.

What is C18 column in HPLC?

C18 columns are HPLC (high performance liquid chromatography) columns that use a C18 substance as the stationary phase. C18 HPLC columns are used in environmental sciences and chemical analysis, as well as industries such as pharmaceutical and environmental sciences, to analyze individual parts of chemical mixtures.

Which gas is used in HPLC?

The sample is carried by a moving carrier gas stream of helium or nitrogen. HPLC has the ability to separate, and identify compounds that are present in any sample that can be dissolved in a liquid in trace concentrations as low as parts per trillion.

### Is TLC polar or nonpolar?

This very polar stationary phase is paired with a relatively nonpolar mobile phase (an organic solvent or solution), in what is referred to as “normal phase” TLC.

Is C18 polar or nonpolar?

A C18 column is an example of a “reverse phase” column. Reverse phase columns are often used with more polar solvents such as water, methanol or acetonitrile. The stationary phase is a nonpolar hydrocarbon, whereas the mobile phase is a polar liquid.

Why is acetonitrile used in HPLC?

Acetonitrile is often used because of its low UV cutoff, lower viscosity (methanol forms highly viscous mixtures with water at certain concentrations), and higher boiling point.

#### Which is better GC or HPLC?

Due to the volatility of the sample and high column temperature, GC happens much faster in comparison to HPLC. GC elution can occur anywhere from a couple of seconds to a few minutes. Ultimately, the speed of elution depends on the sample being tested and the carrier gas flow rate.

#### Is HPLC quantitative or qualitative?

quantitative analysis
The high performance liquid chromatographic – ultraviolet detector (HPLC-UV) is a conventional quantitative analysis method23,24,25,26. In according to the ultraviolet absorption wavelength, elution retention time and chromatographic peak area, the content of compound can be accurately measured27,28,29,30.

Why silica gel is used in TLC?

Silica gel is polar in nature. If we use silica gel as the stationery phase in TLC, we should use some non-polar solvents as a moving or mobile phase, so that separation of the mixture becomes easy and feasible. Hence, all of the above can be used as mobile phase in TLC.

What is Rf value in TLC?

In thin-layer chromatography, the retention factor (Rf) is used to compare and help identify compounds. The Rf value of a compound is equal to the distance traveled by the compound divided by the distance traveled by the solvent front (both measured from the origin).

## Why is silica used in HPLC?

It is a polar absorbent with slight acidity, enabling it to absorb basic contents in a material that needs separation during chromatography, while also remaining neutral and maintaining its own structure throughout the process.