3. Intro to Chromatography

T/F? A.J.P. Martin is credited with coining the term “chromatography” in the 1890s, when he separated plant pigments. (1.3g)

False; Mikhail Tswett

T/F? An HPLC method where the mobile phase composition is held constant through the analysis is called an isocratic method. (1.3h+3.3h)

True; it is isocratic

T/F? The best way to change selectivity in gas chromatography separation is to change the temperature of the column oven/change mobile phase.(1.3e+3.3e)

False; you change the s.p. (based on polarity)

Mikhail Tswett is credited with describing the partitioning model for chromatography (3.3g)

False; A.J.P. Martin

Describe reversed phase liquid chromatography in terms of properties of a) m.p., b) s.p., c) the analytes it can be used to separate, and d) how would the composition of this mobile phase be changed over the course of an analytical run in order to elute a complex mixture of compounds. Provide specific chemical examples for each.  (3.5)

a) m.p. (polar): water (weak) + methanol or acetonitrile (strong)

b) s.p. (nonpolar): C18- (most common), C8-, C4- packed in a stainless steel column

c) Analytes: pharmaceutical compounds, drug metabolites, peptides

d) Starting with a high aqueous (weak) m.p., the m.p. composition is gradually changed through the addition of a greater fraction of polar organic (strong) m.p. component.

Four main instrumental components (besides data station) make up a chromatography instrument. List each of the main components and provide an example of each for both (RP-)HPLC and GC. Be specific. (5.8+6.1)

T/F? Reversed phase LC is used to separate nonpolar analytes based on their degree of hydrophobicity.  (6.2c)

False; it’s polar analytes

T/F? Normal phase LC involves the use of nonpolar m.p. and polar s.p. (6.2i)

True; that’s how normal phase works