1. You will prepare 100 mL of 100 ppm caffeine (MW 194.19 g/mol) in methanol. Th

Question

1. You will prepare 100 mL of 100 ppm caffeine (MW 194.19 g/mol) in methanol. This process requires _________ g of caffeine to be transferred to a 100 mL volumetric flask.

a.10

b.1

c.0.1

d. 0.01

e. 0.001

2. Below are chromatographic data for an injection of a mixture of three species which were made onto a 100 mm column. Species A behaved as a conservative, non-interacting tracer.

Species

Retention Time (min)

Peak width at base (min)

A

1.6

0.46

B

3.5

0.95

C

4.1

1.17

How much time (min) did species C spend in the mobile phase?

a.1.6

b.2.5

c.3.5

d.4.1

e.2.01

Species

Retention Time (min)

Peak width at base (min)

A

1.6

0.46

B

3.5

0.95

C

4.1

1.17

Explanation / Answer

1. You will prepare 100 mL of 100 ppm caffeine (MW 194.19 g/mol) in methanol. This process requires _________ g of caffeine to be transferred to a 100 mL volumetric flask.

Answer:

100ppm means 100mg / Litre or 100mg / 1000mL

So in 100mL the amount will be 10mg

1mg = 0.001 g

so 10mg = 10 X 0.001 g = 0.01 grams

2) time spend = retention time / peak width = 4.1 / 1.17 = 3.5

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