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Chapter 25: Q26P (page 710)

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?

Short Answer

Expert verified

The part (a), part (b) is

  1. It is selected by mass filter Q1 in a triple quadrupole spectrometer and It is selected by mass filter Q3 in a triple quadrupole spectrometer
  2. Internal standard has a nominal mass of 236, so the protonated molecule (right structure on picture) has m/z 237

Step by step solution

01

Propose structures for m/z 234 and m/z 84

Part (a)

At m/z 234, compound has prominent peak, so the structure isMH+:

It is selected by mass filter Q1 in a triple quadrupole spectrometer.

02

C5H10N+

At m/z 84 the fragment is:C5H10N+

It is selected by mass filter Q3 in a triple quadrupole spectrometer.

03

Unlabelled Ritalin will be invisible

Part (b)

The selected reaction monitoring transition that should be monitored to produce a chromatogram of the internal standard in which unlabelled Ritalin will be invisible is m/z

237 84:

Internal standard has a nominal mass of 236, so the protonated molecule (right structure on picture) has m/z 237. Cleavage of bond give the sam fragment as in task (a)

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Most popular questions from this chapter

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

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?

  1. Use equation 25-1to estimate the length of a column required to achieve1.0脳104plates if the stationary phase particles size is10.5,5.0,3.0,or1.5渭尘

  2. If the retention time was 20mins on the 10.0渭尘 particle size column, what is the retention time on the 5.0,3.0,or1.5渭尘columns from part (a)? Assume that flow rate is constant for all columns.

  3. Use equation25-2to estimate the pressure of the column in (a) given that the pressure of the10.0渭尘column was4.4Mpa

  4. If the flow rate was2.0mL/min , what is the baseline width for the peaks on 10.5,5.0,3.0,or1.5渭尘columns form part (a)?

  5. Which of these column configurations would require a UHPLC instrument?

Question: Literature search problem: Human serum albumin (HSA) is an important protein ingredient in cryopreservation media used in procedures such as in vitro fertilization. Search the literature for a high-performance liquid chromatography method for the determination of human serum albumin and the stabilizer N-acetyl tryptophan in medical devices.

(a) Give the citation (authors, title, journal name, year, volume, pages) for the research paper that fits the criteria of this analysis.

(b) What alternative methods could be used for analysis of human serum albumin?

(c) What type of analytical column is used for the separation?

(d) How long was the gradient? How long were the additional wash and equilibration steps within the gradient method?

(e) What parameters were assessed in the method validation?

(f) Why were particles with 300 脜 pores used?

what is the difference between extra-column volume and dwell volume? How do each of these volumes affect a chromatogram?
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