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Question: what are the general steps in developing an isocratic separation for reversed-phase chromatography?

Short Answer

Expert verified

General steps in developing an isocratic separation.

  • determine the analysis's goal.
  • choose a sample preparation method.

Choose a detector that runs a wide gradient to determine whether isocratic

Step by step solution

01

definition an isocratic separation

To create an isocratic separation for reversed-phase chromatography, we need to follow this steps.

  • Determine the analysis's goal.
  • choose a sample preparation method.
  • Choose a detector that runs a wide gradient to determine whether isocratic or gradient elution is appropriate.
02

continue to follow this step

Then,

  • for isocratic elution adjust the mobile phase composition to achieve retention of0.5k20for all compounds.
  • Adjust relative retention by varying the solvent composition, column temperature, organic solvent type, and column type.
  • optimise column dimensions in order to increase plate number or decrease separation time.

Hence,.

  • Determine the analysis's goal. choose a sample preparation method. Choose a detector that runs a wide gradient to determine whether isocratic or gradient elution is appropriate. for isocratic elution adjust the mobile phase composition to achieve retention of 0.5k20for all compounds. Adjust relative retention by varying the solvent composition, column temperature, organic solvent type, and column type. optimise column dimensions in order to increase plate number or decrease separation time.

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Most popular questions from this chapter

(a) Why does mobile phase strength increase as solvent

becomes less polar in reversed-phase chromatography, whereas

mobile phase strength increases as solvent becomes more polar in

normal-phase chromatography?

(b) What kind of gradient is used in supercritical fluid chromatography?

Chromatography鈥搈ass spectrometry. HPLC separation of

enantiomers of the drug Ritalin on a chiral stationary phase was

shown in Problem 25-13.

(a) Detection is by atmospheric pressure chemical ionization with

selected reaction monitoring of the m/z 23484 transitions. Explain

how this detection works and propose structures for m/z 234 and m/z 84.

(b) For quantitative analysis, the internal standardH32-Ritalin with

a deuterated methyl group was added. Deuterated enantiomers have

the same retention times as unlabelled enantiomers. Which selected

reaction monitoring transition should be monitored to produce a

chromatogram of the internal standard in which unlabelled Ritalin

will be invisible?

A bonded stationary phase for the separation of optical isomers has the structure

To resolve the enantiomers of amines, alcohols, or thiols, the compounds are first derivatized with a nitroaromatic group that increases their interaction with the bonded phase and makes them observable with a spectrophotometric detector.

When the mixture is eluted with 20 vol% 2-propanol in hexane, the (R)-enantiomer is eluted before the (S)-enantiomer, with the following chromatographic parameters:

Resolution=螖迟rwav=7.7

Relative retention()=4.53

k for (R)-isomer =1.35

tm=1.00min

wherewavis the average width of the two Gaussian peaks at their base.

(a) Findt1,t2andwawith units of minutes.

(b) The width of a peak at half-height isrole="math" localid="1663582749865" w1/2(Figure 23-9). If the plate number for cach peak is the same, findw1/2for each peak.

(c) The area of a Gaussian peak is1.064peakheightw1/2. Given that the areas under the two bands should be equal, find the relative peak heights(heightR//heightS).

Question:The graph shows retention data from aC8silica column with an acetonitrile/water mobile phase.


(a) What mobile phase composition provides greatest retention(k)for the components? Least retention? Coelution (equalk)of two components?

(b) Predict the retention time of each peak at 40%and60%acetonitrite. Draw a chromatogram (a "stick diagram" representing each peak as a vertical line) of the separation at each mobile phase composition.

(c) Would60%acetonitrile yield adequate resolution?

(d) Assuming Gaussian peaks, does the separation at60%acetonitrile have the attributes of a good separation?

What does it mean for a separation procedure to be 鈥漴ugged鈥 and why is it desirable?

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