/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} QBE A bonded stationary phase for th... [FREE SOLUTION] | 91影视

91影视

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).

Short Answer

Expert verified

a) The values aret1=2.35min,t2=7.11min,wav=0.619min.

b)The half-width of peak 1 is 0.181min.

The half-width of peak 2 is 0.548min .

c) The relative heights of two peaks is 3.0.

Step by step solution

01

Definition of compound

A compound is a substance made up of two or more chemical components that have been chemically bonded together. Covalent bonds and ionic bonds are two typical forms of bonds that hold components in a compound together. In any compound, the components are always present in set ratios.

02

Step 2: Values of t1t2,wav 

a)

To find the retention time of R-isomer,

tmis given as 1.00min.

Retention factor (k) is given as 1.35.

The t1retention time may be computed by substituting the aforementioned numbers in the retention factor equation, as shown below.

k=t1-tmtm=t1-1.001.001.35=t1-1.001.00t1=1.35+1.00t1=2.35min

The R-isomer retention time is computed as 2.35 min.

The retention period of the S -isomer may be calculated using the equation for relative retention.

4.53 is the relative retention.

The retention period for R-isomer is2.35mint1.

Relative retention=tsts1'

4.53=t2-1.00t1-1.00=t2-1.002.35-1.00t2=4.531.351.00=6.11+1.00

The retention time of S-isomer is 7.11min.

To find the average width, divide the whole length by the total width.

The resolution and difference in retention time of the two isomers may be used to compute the average width.

4.77min is the difference in retention time.

In the problem statement, the solution is provided as 7.7.

As demonstrated below, the average width may be computed.

Resolution=tywas7.7=4.77wavwav=4.777.7=0.619min

The average width at the base is calculated as 0.619min.

03

Step 3:Values of w1/2 for each peak

b)

The equation below can be used to compute the plate number.

N=5.54trw1n2

If the plate number is constant, it may deduce that retention time is proportional to half-width.

Hence,

w1npeak1w12peak2=t1t2=2.357.11=0.330

The average width at the base was calculated as0.62min.

It is known that for each peak, the width (w) is equal to4 and half-widthw1n is2.35.

From the above two equations,w was found as1.70w1/2.

The average base width is 0.62min.

wav=12w1+w2=121.70w1/2peak1+1.70w1/2peak2

It is known that

w1/2(peak1)=0.330(w1/2(peak2)

Substituting this into the basic equation's average width

wav=121.700.330w1/2peak2+1.70w1/2peak2=120.561w1/2peak2+1.70w1/2peak21.24=2.26w1/2peak2w1/2peak2=1.242.261=0.548min

The half-width of peak 2 is 0.548min.

As illustrated below, the half-width of peakmay be determined from this.

w1/2peak1=0.330(w1/2peak2=0.3300.548=0.18084min=0.181min

In the provided chromatogram, the half-width of both peaks was calculated.

04

Step 4: Relative peak height

c)

The half-width of peak 1 is 0.181min.

The half-width of peak 2 is 0.584min.

The regions under both peaks are equal, according to the problem statement.

HeightRwR=HeightSwSHeightRHeright=wSwR=0.5480.181=3.0

The relative heights of the two peaks is calculated as 3.0.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

(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

The antitumor drug gimatecan is available as nearly pure (S)-enantiomer. Neither pure (R)-enantiomer nor a racemic (equal) mixture of the two enantiomers is available. To measure small quantities of (R)-enantiomer in nearly pure (S)-gimatecan, a preparation was subjected to normal-phase chromatography on each of the enantiomers of a commercial, chiral stationary phase designated (S,S)- and (R,R)-DACH-DNB. Chromatography on the (R,R)-stationary phase gave a slightly asymmetric peak at tr 5 6.10 min with retention factor k 5 1.22. Chromatography on the (S,S)- stationary phase gave a slightly asymmetric peak at tr 5 6.96 min with k 5 1.50. With the (S,S) stationary phase, a small peak with 0.03% of the area of the main peak was observed at 6.10 min.

Chromatography of gimatecan on each enantiomer of a chiral stationary phase. Lower traces have enlarged vertical scale. [Data from E. Badaloni, W. Cabri, A. Ciogli, R. Deias, F. Gasparrini, F. Giorgi, A. Vigevani, and C. Villani, 鈥淐ombination of HPLC 鈥業nverted Chirality Columns Approach鈥 and MS/MS Detection for Extreme Enantiomeric Excess Determination Even in Absence of Reference Samples.鈥 Anal. Chem. 2007, 79, 6013.]

(a) Explain the appearance of the upper chromatograms. Dashed lines are position markers, not part of the chromatogram. What Problems 709 would the chromatogram of pure (R)-gimatecan look like on the same two stationary phases?

(b) Explain the appearance of the two lower chromatograms and why it can be concluded that the gimatecan contained 0.03% of the (R)-enantiomer. Why is the (R)-enantiomer not observed with the (R,R)-stationary phase?

(c) Find the relative retention (a) for the two enantiomers on the (S,S)-stationary phase.

(d) The column provides N 5 6 800 plates. What would be the resolution between the two equal peaks in a racemic (equal) mixture of (R)- and (S)-gimatecan? If the peaks were symmetric, does this resolution provide baseline separation in which signal returns to baseline before the next peak begins?

The rate at which heat is generated inside a chromatographycolumn from friction of flowing liquid is power (watts, W=J/s)= volume flow raterole="math" localid="1656474760665" (m3/s)pressure drop (pascals, role="math" localid="1656474828044" Pa=kg/[m?s2]).

(a) Explain the analogy between heat generated in a chromatography column and heat generated in an electric circuit (power = currentvoltage).

(b) At what rate (watts = J/s) is heat generated for a flow of 1 mL/minwith a pressure difference of3500 bar between the inlet and outlet?

You will need to convert mL/min tom3/s.Also 1 bar=105Pa.

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.

See all solutions

Recommended explanations on Chemistry Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.