GC Inlet Gas Expansion Volume Calculation: V = (nRT) / P
V = volume in mL
P = pressure (psi)
n = moles = mass / molar mass
R = gas constant
T = temperature (K)
Example, at 250οC and 15psi, a 2.0μL injection of methylene chloride (density = 1.326kgL-1 and 85gmol-1) will expand to 0.66mL
0.66mL = {[(2.0 x 10-6 L x 1.326kgL-1) / 85 x 10-3 kgmol-1] x [0.08206Latmmol-1K-1 x 523K]} / {(15 + 14.7) / 14.7 atm)}
GC Inlet Liner Volume Calculation
Volume = Length x πr2
| Capacity Factor (k'): k' = |
tr — t0 |
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t0 |
t0 = time for the solvent peak to elute
tr = retention time of analyte
| Efficiency (Theoretical Plates): |
( |
tR |
) |
2 |
N = 5.54 |
W1/2 |
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5.54 is a constant when using the "Half Height" method.
tR is the retention time of the peak and W1/2 is the width at half height.
| Resolution: Rs = (1/4)[(α-1)/α](N)1/2[k'/(1+k')] |
k' = the average of two peaks
Selectivity (Alpha Value): α = k'2 / k'1
k' = capacity factor
| Peak Assymetry: Ps = B/A (at 10% peak height) |
A = At 10% peak height, the width of a line from the slope to a perpendicular line drawn from the peak's height to the baseline @ 10% height. A is the fronting part of the chromatogram.
B = At 10% peak height, the width of a line from the slope to a perpendicular line drawn from the peak's height to the baseline @ 10% height. B is the tailing end of the chromatogram.
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