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The number of theoretical plates in a chromatography column is a measure of how "long" the column is - how well it separates. A "short" column will only separate large or heavy molecules, and the medium and light stuff is still mixed together in the last band. A "long" column will separate the little stuff better because there are more theorectical plates.

Picture a stack of sieves with smaller and smaller holes as the column gets "longer" and you've got the idea.

This "length" has virtually nothing to do with the physical length of the separating column. It is a function of the packing materials and solvents used during a separation.

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What are the usp limits for the theoretical plates in gas chromatography?

There is no "limit" set by the USP, it depends on the molecules and what is reasonable. For example in HPLC, 2000 plates is typically what you would like to shoot for but if its a compound with low sensitivity and you need to see low levels you might inject more compound which would increase sensitivity but also probably affect peak shape and thus theoretical plates. The answer is it depends


What are the advantages and limitations of column chromatography over thin layer chromatography?

TLC. The mobile phase is a liquid, the stationary phase is a solid. Useful for seperating and comparing mobility of solids and some liquids dissolved in the mobile phase by their affinities to the solid phase relative to the mobile phase. GLC. The mobile phase ia s gas, the stationary phase is a liquid on a solid support. same concept as TLC. useful for seperating gases by their affinities to the stationary phase...the mobility can then be compared to known compounds for possible identification.


If your first distillate was 49 mole percent methanol how many theoretical plates were in your distillation setup?

There is quite a bit of missing information here.a. Lets assume your pressure is 1 atm.b. Lets also assume you are distilling methanol and water.c. Lets assume your theoretical plate efficiency is 100%d. Lets ALSO assume your initial concentration is 0.1 mol% methanol.Given these condition it takes about 1.25 theoretical plates to distill it to about 49 mol%.The number of plates depends heavily on the initial concentration.Working backwards from 49mol%, exactly one stage would place you at an initial concentration of about 8%. Exactly two would place you at about 1 mol%.See also the McCabe Thiele method: http://en.wikipedia.org/wiki/McCabe-Thiele_method


What are the characteristics of a TLC plate that make it more polar compared to other types of plates?

A TLC plate is more polar compared to other types of plates because it is made of a material that attracts polar molecules more strongly. This material has a higher affinity for polar substances, causing them to move more slowly on the plate during chromatography.


How can paper chromatography be used to separate pigments based on their chemical and physical properties?

It is an appropriate technique to use because it separates the pigments, so one can see which pigments are present, even if some pigments are normally hidden to the naked eye.

Related Questions

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Why it is said that number of theoretical plates should be high for a good efficiency?

In liquid chromatography the 'theoretical plates' number is a measure of the resolution between the peaks of different eluting substances. The higher the plate value the greater the separation. This is particular important as the load reaches the maximum the column is designed for.


What is 16 in the formula of no. of theoretical plates?

In the context of distillation and chromatography, the term "16" often refers to the empirical formula used to estimate the number of theoretical plates (N) in a column or separation process. This formula is derived from the relationship between the height of a theoretical plate (H) and the overall column height (L), expressed as ( N = \frac{L}{H} ). The number 16 is commonly associated with the simplified relationship N = (16)(\frac{L}{H}), indicating that the efficiency of a separation process can be linked to the design and operational parameters of the column.


What is the efficiency of packed columns in gas chromatography?

It is around 4000-6000 plates for a 2 meter column.


Where I can buy Silica Gel TLC Plates for Column Chromatography?

you can find these items in alibaba or sigmaaldrich website.


What are the usp limits for the theoretical plates in gas chromatography?

There is no "limit" set by the USP, it depends on the molecules and what is reasonable. For example in HPLC, 2000 plates is typically what you would like to shoot for but if its a compound with low sensitivity and you need to see low levels you might inject more compound which would increase sensitivity but also probably affect peak shape and thus theoretical plates. The answer is it depends


What is a column plate number?

It is the efficiency of the column. The larger the number, the more theoretical plates the column possesses; a typical well-packed column with a 5-micrometer particle size porous packing in a 15cm x 46 mm column should provide10,000-20,000 plates. sorry. I forgot to put a point in there. It should be 4.5 mm, not 45


What is the purpose of Reflux in an oil refinery?

The reflux is the return of top product condensate from a distillation column back to the top of the column where it is able to flow down the column aiding with cooling and thus condensation in the column. It increases efficiency and enables a lower amount of theoretical plates to be used in the column.


Why are glass beads used in a fractionating column?

Glass beads are used in a fractionating column to provide surface area for vapor-liquid contact and enhance the separation of components in a mixture. The beads help in achieving more efficient distillation by increasing the number of theoretical plates, which improves the separation efficiency of the column.


What height a fractional distillation column has?

The height of a column used in fractional distillation is dependent on the number of theoretical plates needed to sufficiently separate a mixture divided by the height equivalent to theoretical plate HETP. Nt=H/HETP


What Variables that affect column chromatography?

Answer:The factors which affect the chromatography are:TemperaturePressureFlow rate of mobile phaseSample preparation


What are the advantages and limitations of column chromatography over thin layer chromatography?

TLC. The mobile phase is a liquid, the stationary phase is a solid. Useful for seperating and comparing mobility of solids and some liquids dissolved in the mobile phase by their affinities to the solid phase relative to the mobile phase. GLC. The mobile phase ia s gas, the stationary phase is a liquid on a solid support. same concept as TLC. useful for seperating gases by their affinities to the stationary phase...the mobility can then be compared to known compounds for possible identification.