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Total Flow Formula:
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Total Flow in gas chromatography represents the sum of carrier gas flow and makeup gas flow through the chromatographic system. It determines the overall gas velocity and affects separation efficiency and detection sensitivity.
The calculator uses the simple addition formula:
Where:
Explanation: The total flow is the combined gas flow that reaches the detector, influencing peak shape, retention times, and detector response.
Details: Accurate total flow calculation is essential for optimizing chromatographic conditions, ensuring proper detector operation, and maintaining consistent analytical performance across different methods and instruments.
Tips: Enter carrier gas flow and makeup flow in mL/min. Both values must be non-negative. Typical carrier flows range from 1-5 mL/min, while makeup flows vary by detector type and method requirements.
Q1: Why is total flow important in GC?
A: Total flow affects residence time in the detector, peak broadening, signal-to-noise ratio, and overall chromatographic efficiency.
Q2: What are typical total flow values?
A: Typical total flows range from 10-60 mL/min depending on the detector type, with FID commonly using 30-50 mL/min total flow.
Q3: When should makeup gas be used?
A: Makeup gas is often used with capillary columns to maintain optimal linear velocity through the detector, especially with detectors like ECD or NPD.
Q4: How does total flow affect detection?
A: Insufficient total flow can cause peak tailing and reduced sensitivity, while excessive flow may dilute samples and decrease detector response.
Q5: Can this calculator be used for all GC detectors?
A: Yes, the total flow calculation applies to all GC detectors, though optimal flow rates vary by detector type and manufacturer specifications.