Two interesting and fairly recent trends in GC systems are “fast GC” and the use of hydrogen as the carrier gas. Hydrogen is much less expensive than helium. It also has superior optimal linear velocity and produces a very low effective plate height, meaning more theoretical plates are available for a given column length. Because of its lower density relative to helium, hydrogen works extremely well with very narrow-bore columns. Fast GC provides benefits of lower instrument and human resource costs, higher revenues for high-throughput testing or service labs, and more rapid method development. Perhaps best of all, these benefits accrue with no additional capital investment. Ultra-high-performance liquid chromatography, by comparison, requires purchasing an instrument capable of generating and withstanding high backpressures. Fast GC is achieved by shortening column length, ramping up temperatures faster, and raising the carrier gas flow rate. The negative effects on resolution are countered by narrowing the column’s internal diameter, reducing the film thickness, and (a second trend) switching from helium to hydrogen carrier.

According to Agilent Technologies’ website, troubleshooting your GC system starts with isolating the problem:

Is it injection, flow, column, detection, electronic or some combination?

The company adds users should know what can and can’t cause the symptom and what to do about it:

• Broad solvent peak–injector problems, technique, sample problems
• Split peaks–injector problems, mixed solvent
• No peaks –wasn’t introduced, wasn’t detected
• Bonus peaks–In Sample or Back Flash
• Response changes–activity, inlet discrimination, detector problem
• Peak tailing–flow path or activity
• Peak fronting–overload or solubility mismatch
• Shifting retention–leaks, column aging, contamination or damage
• Loss of resolution–peak broadening, separation decreasing
• Baseline disturbances–column bleed, contamination, temperature
• Noisy or spiking baseline–electrical or contaminated detector
• Negative or flat-topped peaks–detector problems
• Quantitation problems–activity, inlet or detector problems

Troubleshooting tips courtesy of Agilent Technologies

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