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A known mixture of compounds A and B gave the following HPLC results:

A solution was prepared by mixing 12.49mgof Bplus 10.00mLof unknown containing just and diluting to 25.00mL. Peak areas of 5.97and 6.38were observed for AandB, respectively. Find the concentration of A(mg/mL)in the unknown.

Short Answer

Expert verified

The concentration of Ais 0.418mg/mL..

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

The concentration of A(mg/mL) in the unknown.

PeakareaofAis5.97.PeakareaofBis6.38.AreaAA=FAreaBB10.861.03=F4.371,16F=10.86|1.03||1.16]4.37=12.59764.5011=2.789=2.7925.00mListhetotalvolumeoftheunknownsolution.TheadditionalweightofBis12.49g.ThetotalvolumeofAthathasbeenaddedis10mL.Asdemonstratedbelow,theconcentrationofBintheunknownsolutionmaybedetermined.

12.49g/25.00ml=0.4996g/mL

Theconcentrationofisrepresentedbelow.ArcaAA=FArcaBB5.97A=2.796.380.4996A=5.972.7910.4996]6.38=2.98261217.8002=0.1675g/mLTheconcentrationofAintheinitialunknownsolutionisdeterminedtobeasfollows:Ainoriginalunknown=25.0010.00(0.167mg/mL)=0.418mg/mLTherefore,theconcentrationofAintheunknownisfoundas0.418mg/mL.

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Most popular questions from this chapter

In monolithic columns60 the stationary phase is a single porous piece of silica or polymer filling the entire column and synthesized within the column from liquid precursors. Monolithic columns offer similar plate height to HPLC particles, but with less resistance to flow. Therefore, faster flow or longer columns can be used. The figure shows separation of isotopic molecules on a long monolithic column. Packed columns have too much resistance to flow to be made so long.

Separation of isotopic molecules on a 440-cm-long monolithic C18-silica column eluted withCH3CN/H2O(30: 70 vol/vol) at 308C. [Data from K. Miyamoto, T. Hara, H. Kobayashi, H. Morisaka, D. Tokuda, K. Horie, K. Koduki, S. Makino, O. Nu帽ez, C. Yang, T. Kawabe, T. Ikegami, H. Takubo, Y. Ishihama, and N. Tanaka, 鈥淗igh-Efficiency Liquid Chromatographic Separation Utilizing Long Monolithic Silica Capillary Columns,鈥 Anal. Chem. 2008, 80, 8741.]

(a) Unretained thiourea is eluted in 41.7 min. Find the linear velocity ux (mm/s).

(b) Find the retention factor k forC6D6

(c) Find the plate number N and plate height forC6D6

(d) Assuming that the peak widths forC6H5Dand C6D6are the same as that of C6D6, find the resolution of C6H5Dand C6D6.

(f) If we just increased the column length to increase N, what value of N and what column length would be required for a resolution of 1.000?

(g) Without increasing the length of the column, and without changing the stationary phase, how might you improve the resolution?

(h) When the solvent was changed fromCH3CN/H2O(30:70 vol/vol) toCH3CN/CH3OH/H2O(10:5:85), the relative retention for C6H5D andC6D6increased to 1.0088 and the retention factor for C6H6 changed to 17.0. If the plate number were unchanged, what would be the resolution?

(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?

a. Why are HPLC particles porous?

b. Why are the particles with60-120Apores used for small molecules but wide pore300-Astationary phases used to separate polypeptides and proteins?s

To which kinds of analytes do these liquid chromatography detectors respond?

(a) ultraviolet

(b) refractive index

(c) evaporative light scattering

(d) charged aerosol

(e) electrochemical

(f) fluorescence

(g) nitrogen chemiluminescence

(h) conductivity

The figure shows the separation of two enantiomers on a chiral stationary phase.


Sepation of enantiomers of Ritalin by HPLC with a chiral stationary phase.[Data from R.Bakhitar,L.Ramos,and F.L.S.Tse, 鈥淨uantification of methlylphenidate in plasma using chiral Liquid-chromatography/Tandem mass spectrometry: Application to Toxicokinetric studies,鈥滱nal Chim Acta 2002,469,261.]

(a)From trandw1/2 find N for each peak.

(b) Fromtrandw1/2find the resolution.

(c)Giventm=1.62min, use Equation23-23with the average N to predict the resolution.

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