GC-FID Gas Chromatograph Flame Ionization Detector Simulation

GC Method Timeline

Initialize

Equilibrate

Inject

Separate

Detect

Report

✓Carrier Gas Flowing (Helium)

✓Oven Equilibrated (60 °C)

✓Detector Ready (FID Flame Lit)

○Sample Injected

Carrier GasHelium (35 cm/s)

Oven Temp60.0 °C

InjectionSplit (1:20)

FID Signal0.50 pA

Run Time0:00 min

GC-FID Real-Time Chromatogram

● IDLE Selected Peak: None

              ACQUISITION PROGRESS: 0%
              TIME REMAINING: 8:00 min
            

💡 Why Did This Peak Move? (Parameter Impact Guidance)

Configure method parameters (Carrier Gas, Oven Temp Ramp, Injection Mode) and click "▶ Start Chromatogram Run" to observe peak retention time shifts.

SAMPLE MIXTURE

CARRIER GAS

INJECTION MODE

Split Splitless

Split Ratio:1:20

Initial Oven Temp:60 °C

Oven Ramp Rate:10 °C/min

SPEED:

Peak Integration & Quantitation Table (USP <467>)

Peak #	Compound	t_R (min)	Height (pA)	Area (pA·s)	Width (min)	% Area	Status

🎓 Gas Chromatography & FID Separation Masterclass

Master open-tubular capillary column gas dynamics, Golay band broadening kinetics, oven temperature programming, and Flame Ionization Detection (FID) response factors.

💨 Interactive Carrier Gas Kinetics & Golay Equation Sandbox (H vs u)

For wall-coated open tubular (WCOT) capillary columns ($A = 0$), the Golay equation $H = \frac{B}{u} + (C_s + C_m) u$ governs efficiency:

Linear Velocity (u): u = 45.0 cm/s

Plate Height (H)

0.28 mm

Theoretical Plates (N)

107,000 plates

💡 Why Hydrogen wins: Fast molecular diffusivity ($D_g$) keeps the $C$-term flat at high velocity, enabling 2x faster run times at $45\text{ cm/s}$ with near-zero loss in separation efficiency.

Golay Curve H vs Linear Velocity u

── N₂ (u_opt=15) ── He (u_opt=35) ── H₂ (u_opt=45)

🌡️ Oven Temperature Programming & The General Elution Problem

Solve early-peak congestion and late-peak broadening in complex volatile mixtures:

Linear Temperature Program (50°C → 250°C)

As the oven temperature rises linearly, vapor pressures of high-boiling analytes increase exponentially, accelerating their migration down the capillary column.

Uniform Peak Widths: Unlike isothermal runs, all peaks maintain narrow, sharp gaussian shapes throughout the chromatogram.
Short Analysis Time: High-boilers (e.g. C20:4 FAMEs, Geraniol) elute in minutes rather than hours.
Improved Detection Limits: Taller, narrower peaks dramatically improve signal-to-noise ratio ($S/N$).

🪜 Kovats Retention Index (I) Derivation & n-Alkane Scale

The Kovats Retention Index ($I$) normalizes retention times relative to homologous $n$-alkanes ($C_z$, where $I = 100 \times z$), making chromatographic data universally reproducible across different column lengths, carrier gas velocities, and lab models: I = 100 · [z + (log t'Rx - log t'Rz) / (log t'R(z+1) - log t'Rz)]

C5 – C7 (Solvent Volatiles)

I = 500 – 700 (Low boiling point < 90°C)

Methanol (530), Acetaldehyde (570), Ethanol (590), Benzene (662)

C7 – C10 (Aromatics & Solvents)

I = 700 – 1000 (Boiling point 90 – 160°C)

Toluene (770), Acetone on DB-624 (796), Ethylbenzene (866), α-Pinene (939)

C10 – C14 (Terpenes & Congeners)

I = 1000 – 1400 (Boiling point 160 – 230°C)

Limonene (1031), Linalool (1099), Menthol (1169), Geraniol (1256)

C14 – C24 (Lipid FAMEs)

I = 1400 – 2500 (Fatty Acid Methyl Esters)

C14:0 Myristate (1725), C16:0 Palmitate (1924), C18:0 Stearate (2121), C20:4 (2446)

🔥 FID Effective Carbon Number (ECN) & Response Factor Calculator

The Flame Ionization Detector (FID) produces current proportional to oxidizable carbon atoms forming $\text{CHO}^+$ ions in a Hydrogen/Air flame. Non-hydrocarbon functional groups reduce the effective carbon count per Sternberg's empirical rules:

SELECT SAMPLE ANALYTE FOR ECN CALCULATION

Total Carbon Count

2 Carbon Atoms

Effective Carbon (ECN)

ECN = 1.50

Primary alcohol carbon bonded to -OH has reduced ionization efficiency ($2.0 - 0.5 = 1.50\text{ ECN}$).

Sternberg FID Response Contribution Rules

Structural Group	Contribution	Rationale
Aliphatic Carbon (-CH₃, -CH₂-)	+1.00	Full flame ionization to CHO⁺
Aromatic Carbon (Ar-C)	+1.00	Benzene ring carbons
Primary Alcohol (-CH₂OH)	-0.50	Partial oxidation to CO
Carbonyl Carbon (C=O)	-1.00	Carbonyl carbon forms CO (0% FID ion)
Ester Carbon (-COO-)	-1.50	Carbonyl + ether oxygen penalty
Chlorine Atom (-Cl)	-0.12	Flame radical scavenging