HPLC column with 150 length and 4.6 mm I.D. packed with nonporous spherical particles of 1 𝜇 diameter. Column void volume is 1.3 mL. Calculate total surface area of adsorbent in the column. Explain.
Polystyrene sample with 66,000 Da molecular weight (polydispersity = 1.04) give 0.89 mL retention from tetrahydrofuran on RP column (100 x 4.6 mm) with 95 m2 total surface area. Column void volume is 1.1 mL. Calculate the gyration radius of polystyrene in THF. Explain.
What is the void volume of the column with the following parameters: Interparticle volume = 1.0 mL. Column packed with spherical particles with diameter = 5 𝜇. Adsorbent pore volume = 1.2 mL/g Density of bulk silica = 2.2 g/mL, adsorbent weight = 0.58 g.
One acidic analyte has pKa=5.8 and another basic analyte has pKa=6.2 what should be the pH of aqueous portion of mobile phase and acetonitrile composition to have at least 90% of both analytes in neutral form?
HPLC analysis of ionizable analytes is better to perform at low pH when they are fully ionized (2 pH units lower than analyte pKa). For basic analyte with pKa = 3.4 and 30/70 acetonitrile/water eluent composition what should be the pH of an aqueous portion of the mobile phase to ensure that analyte is in its neutral form?
Column has 15,000 TP efficiency, 0.9 mL void volume. Average system band broadening coefficient is 10 (this means that not retained component expands 10 times, e.g., if you inject 10 𝜇L volume the non-retained component peak will be 100 𝜇L wide). With the flow rate 1 mL/min calculate approximate retention volumes where band broadening become negligible for injections of 1 𝜇L; 10 𝜇L and 100 𝜇L (broadening effect is less than 5%).
One column has 1.7 mL void volume and 1.0 mL interparticle volume and another column packed with the same adsorbent shows 1.9 mL void volume and 1.36 mL interparticle volume. Dimensions of both columns are the same. Compare possible chromatographic behavior of both columns (what can you say about their chromatographic behavior and packing quality?
Which elution order you might expect in CZE for the following components: benzene, benzoic acid, aniline, phenobarbital at pH = 2 and at pH = 7. How will it change if you add 5% Trimethyldodecylammonium chloride in your buffer? Describe for both given pH values.
You were asked to evaluate the results of GPC analysis of PMMA (poly[methyl methacrylate]) polymer. Separation was made on PLGel universal column (styrene-divinylbenzene 100 – 107 separation range), RI detection, and eluent – THF, calibration by polystyrene standards. Weight and number average values were calculated directly from chromatogram. Are calculated Mw and Mn values correct? Explain why.
You are separating benzene, toluene and ortho-nitrophenol on RP column with acetonitrile/water as eluent. How the variation of the eluent composition (% of acetonitrile in water) will affect the selectivity between benzene and toluene and between o-nitrophenol and benzene? Explain.
