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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?

Two peaks emerge from a reversed-phase chromatography column as sketched in the illustration.

According to Equation 23-33, resolution is given by

Resolution=N4(-1)(k21+k2)

where Nis plate number, is relative retention (Equation23-20), and k2 is the retention factor for the more retained component (Equation 23-16).

(a) If you decrease the amount of organic solvent in the mobile phase, you will increase retention. Sketch the chromatogram if retention factors increase but Nand are constant.

(b) If you change the solvent type or the stationary phase, you will change the relative retention. Sketch the chromatogram ifincreases but Nandk1are constant.

(c) If you decrease particle size or increase column length, you can increase the plate number. Sketch the chromatogram if Nincreases by (i) decreasing particle size and (ii) increasing column length. Assume and k2are constant.

a) UHPLC can provide exquisite resolution when run slowly on long columns or rapid separation with reasonaple resolution if short columns are run fast. the drug acetaminophern run on a 502.1mmc18UHPLC column has a retention time of 0.63min and a width at half-height of 2.3s.Find the plate number and plate height. How many1.7渭尘 diameter particles places placed dide-by are equal to one theoretical plate?

b) From figure25-3,we expect an optimum plate height of 4渭尘 how many particles placed side-by- side are equal to one theroretical plate? Do you think the column in (a) is being run for maximum resolution or maximum speed?

(a) Nonpolar aromatic compounds were separated by HPLC on an octadecyl(C18)bonded phase. The eluent was 65 vol% methanol in water. How would the retention times be affected if 90% methanol were used instead?

(b) Octanoic acid and 1-aminooctane were passed through the same column described in (a), using an eluent of 20% methanol/80% buffer (pH 3.0). State which compound is expected to be eluted first and why.

role="math" localid="1656416023291" CH3CH2CH2CH2CH2CH2CH2CO2HOctanoicacidCH3CH2CH2CH2CH2CH2CH2CH2NH21Aminooctane

(c) Polar solutes were separated by hydrophilic interaction chromatography (HILIC) with a strongly polar bonded phase. How would retention times be affected if eluent were changed from 80 vol% to 90 vol% acetonitrile in water?

(d) Polar solutes were separated by normal-phase chromatographyon bare silica using methyl t-butyl ether and 2-propanol solvent. How would retention times be affected if eluent were changed from 40 vol% to 60 vol% 2-propanol? (Hint: See Table 25-4.)

use figure 25-17to suggest which type of liquid chromatography you could use to separate compounds in each of the following categories.

(a)Molecular mass <2000,soluble in octane

(b) Molecular mass <2000 ,soluble in methanol-water mixtures

(c) Molecular mass <2000 ,weak acid

(d)Molecular mass<2000 ,soluble highly polar

(e) Molecular mass <2000 ,ionic

(f)Molecular mass<2000,soluble in water in nonionic various

(g) Molecular mass<2000,soluble in water in water, variety of changes

(h) Molecular mass<2000,soluble in tetrahydrofuran

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