Answers to Questions - Forensic Applications of Gas Chromatography - page 143

5. Based on your answers to question 3.3 and using Equation (3.6),
calculate the height equivalent to a theoretical plate (in units of
millimetres).
Answer:

(a):

HETP = L/N

HETP = 30,000 mm/69,488

HETP = 0.43 mm

( b):

HETP = L/N

HETP = 30,000 mm/93,626

HETP = 0.32 mm

(c):

HETP = L/N

HETP = 30,000 mm/106,276

HETP = 0.28 mm

6. A compound with a retention time of 6.3 min and a peak height of
624,352 (μV) has been assessed for peak asymmetry at (a) 10% of its
peak height to have a value for 'a' of 1.8 s and a value for 'b' of 2.2 s,
and (b) 5% of its peak height to have a value for 'a' of 2.0 s and a value
for 'b' of 2.5 s. Calculate the peak asymmetry using Equations (3.7)
a nd (3.8).
Answer: Using Equation (3.7) at 10% of the peak height and referring
to Figure 3.3:

A s = b/a (3.7)

A s = 2.2 s/1.8 s

A s = 1.22 (no units)