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Chapter 25: Q33P (page 710)

(a) use figure 25-28a select a tetrahydrofurn/water mobile phase strength of equivalent strength to 80%methanol.

(b)Describe how to prepare 1 L of this tetrahydrofurn mobile phase.

(c)what limitation would be imposed by the use tetrahydrofurn.

Short Answer

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a) 53%

b)To prepare 1 L of this tetrahydrofuran mobile phase (53 %), we need to mix 530 mL of tetrahydrofuran with 470 mL of water.

c) The limitations that would be imposed by the use of tetrahydrofuran is that it absorbs UV radiation and attacks polyether, ether, ketone and plastic components.

Step by step solution

01

Definition of water mobile phase of equivalent strength

The weak solvent is commonly referred to as the A-solvent (percent A), and the strong solvent is referred to as the B-solvent ( percent B). The mobile phase is typically a mixture of A- and B-solvents, such as 40% buffer and 60% methanol (abbreviated 60 percent B).

a) Figure 25-28 depicts a nomograph of the volume percentage of solvents with the same eluent strength.

At the same eluent strength, a vertical line intersects each solvent line.

Tetrahydrofurn mobile phase

b) The figure shows that 53 percent of the tetrahydrofuran/water mobile phase strength is equivalent to a concentration of 80% methanol.

To prepare 1 L of this tetrahydrofuran mobile phase (53%), we need to mix 530 mL of tetrahydrofuran with 470 mL of water.

02

Limitations of tetrahydrofuran

c) The limitations that would be imposed by the use of tetrahydrofuran is that it absorbs UV radiation and attacks polyether, ether, ketone and plastic components.

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Most popular questions from this chapter

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(伪)=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 is1.064脳peakheight脳w1/2. Given that the areas under the two bands should be equal, find the relative peak heights(heightR//heightS).

Microporous silica particles with a density of2.2g/mLand a diameter10渭尘of have a measured surface area of calculated the surface area of the300m2spherical silica as if it were simply solid particles what does this calculation tell you about the shape or porosity of the particles.

Use Figure 25-30 for the following questions:

(a) What pH would be best for the separation of benzoic acid, 4-nitrophenol, and 3-methylbenzoic acid?

(b) What pH would be best for the separation of benzoic acid, 3-methylbenzoic acid, and 4-methylaniline?

(c) What pH would be best for separation of 4-nitrophenol, 4-methylaniline, and codeine on a typical C18-silica column?

A mixture of 14compounds was subjected to a reversed-phase gradient separation going from 5%to 100%acetonitrile with

a gradient time of 60min. The sample was injected at t =time. All peaks were eluted between 22and 50min.

(a) Is the mixture more suitable for isocratic or gradient elution?

(b) If the next run is a gradient, select the starting and ending %acetonitrile

and the gradient time.

Morphine and morphine 3-b-d-glucuronide were separated on two different 50 3 4.6 mm columns with 3-mm particles.61 Column A was C18-silica run at 1.4 mL/min and column B was bare silica run at 2.0 mL/min.

(a) Estimate the volume,Vm, and time,tm, at which unretained solute would emerge from each column. The observed times are 0.65 min for column A and 0.50 min for column B.

(b) Column A was eluted with 2 vol% acetonitrile in water containing 10 mM ammonium formate at pH 3. Morphine 3-尾-d-glucuro-nide emerged at 1.5 min and morphine at 2.8 min. Explain the order of elution.

(c) Find the retention factor k for each solute on column A, usingtm5 0.65 min.

(d) Column B was eluted with a 5.0-min gradient beginning at 90 vol% acetonitrile in water and ending at 50 vol% acetonitrile in water. Both solvents contained 10 mM ammonium formate, pH 3. Morphine emerged at 1.3 min and morphine 3-b-d-glucuronide emerged at 2.7 min. Explain the order of elution. Why does the gradient go from high to low acetonitrile volume fraction?

(e) From Equation 25-12 in Box 25-4, estimate k* on Column B assuming S = 4 and withtm5 0.50 min.
See all solutions

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