(CHINH 16. Polarities of analyte functional group increase in the order of hydrocarbon ethers

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Chinh 16 Polarities Of Analyte Functional Group Increase In The Order Of Hydrocarbon Ethers Esters Ketones Aldehyd 1 (61.8 KiB) Viewed 71 times

(CHINH 16. Polarities of analyte functional group increase in the order of hydrocarbon ethers <esters <ketones < aldehydes < amides amines <alcohols Arrange the order of elution [from shortest to longest retention time] for the following six compounds from an HPLC C column. CH OH CH,COCH CH.COOH CH,COOCH, CHOCHE A CH4OH < CHÚCOOH < (CHINH • CHÚCOCH • CHUCOOC3H, CHOC2H5 B. CH3COOH=CH-OH (CH, NHẤCH COCH=CHCOOCH=CH-OC C CHI OH=CH-COOH < (CH) NH<CHÚCOCH=CH-OCH • CHCOOCH3 D. CH.COOH < C.H.OH (CH),NH <CH.COCH, <C,H,OCH <CH.COOCH, E. CHCOOH <CH,OH < (CH), NH CH.COOCH, <CH,COCH, C.HOC Hs 17. Injection of ethane, propane, butane, pentane, and hexane on a squalene column under isothermal conditions gives retention times of 3 51,498, 730, 11.00, and 16.85, respectively. Air, which is nonretained, elutes at 1.00 min. An injection of pyridine under the same conditions gives a retention time of 10.05 min. What is the Kováts retention index for pyridine under these conditions? A. 485 B. 478 C. 370 D. 334 E 300 18. An LC separation specifies that the mobile phase be 25% tetrahydrofuran (THF) in water. Unfortunately, the laboratory supply of THF is temporarily exhausted. Thus, the mobile phase is made with acetonitrile (CH-CN) instead. What is the ratio of CH.CN/H 0 that has the same strength? Solvent HO CH.CN CH,OH THE P 10.2 3.1 4.0 5.8 A 33% B. 349 C. 35% D 36% E 37% 19. Scientists determined the %w/w H2O in methanol by GC, using a capillary column coated with a nonpolar stationary phase and a TCD detector. A linear regression gives a relationship between %w/w H20 (x) and Peak Height () as follows: y=46.57x+0.2234 Calculate the %w/w H:0 in a sample giving a peak height of 6.73. A. 0.131 B 0.140 C. 0.149 D. 0.015 E. 0.652 20. Which of the following is NOT true of reverse-phase HPLC? A. Solvents are degassed to ensure that there are no gas bubbles in the mobile phase. B. The stationary phase is usually silica beads with a hydrophilic coating. C. Compounds are eluted in order of decreasing polarity. D. The mobile phase is usually a mixture of water and an organic solvent. E. Reversed-phase HPLC separates molecules based on surface hydrophobicity.