Q: Why does the site say “<155 nm” instead of an exact lower bound?

GC-UV detection extends well into the vacuum-UV, but the exact lower wavelength a given system reaches depends on the flow cell design, window material, carrier-gas purity, optical path length, and the absorbing species in the sample. Quoting a single fixed number would imply a guaranteed limit across all configurations and matrices, which isn't physically accurate. “<155 nm” communicates the meaningful capability — operation in the vacuum-UV — without overstating performance you can't reproduce in your own setup.

Q: What actually limits the lower wavelength?

Three things dominate: (1) absorption by the carrier gas itself (N₂ is largely transparent down to ~145 nm; O₂ and H₂O cut in much earlier), (2) the transmission cutoff of the flow-cell windows (MgF₂, LiF, and synthetic silica each have different deep-UV cutoffs), and (3) lamp emission and detector quantum efficiency at very short wavelengths. INSCAN is engineered so all three are pushed as far into the vacuum-UV as the application requires.

Q: Does GC-UV always operate at the lowest possible wavelength?

No — and it shouldn't. The optimal wavelength window is chosen per analyte. Many compound classes have their strongest, most selective absorption bands above 155 nm. Going lower buys you sensitivity for non-UV-active compounds and class-level fingerprints, but it isn't free: shorter wavelengths require stricter purge, cleaner gas, and shorter optical paths.

Q: How should I interpret the spec sheets?

Treat the published range (typ. <155–330 nm) as the envelope INSCAN can operate within. The wavelength range that's relevant to your method is a subset chosen during method development, based on your analytes, matrix, and required limits of detection. Our applications team confirms the working window during a feasibility scan.

Q: Is “<155 nm” a marketing hedge?

It's the opposite — it's the honest framing. A specific sub-155 nm number would only be defensible under one configuration with one sample. The “<155 nm” phrasing matches how peer-reviewed GC-UV literature describes vacuum-UV operation, and it's consistent with how spectroscopy vendors quote ranges (e.g. “below 200 nm” for deep-UV HPLC detectors).

Q: What does “far below 155 nm” actually mean in practice?

“Far below 155 nm” means the optical path is engineered to keep transmitting useful signal deep into the vacuum-UV — typically into the 130–150 nm region, and in some configurations approaching the LiF cutoff near 105 nm. In that regime almost every organic molecule has a strong σ→σ* or n→σ* absorption, so even compounds that look “UV-transparent” in conventional HPLC detectors (alkanes, fixed gases, simple halocarbons) become detectable with class-specific spectra.

Q: What limits performance at the deepest wavelengths?

Four things, in order of impact: (1) residual O₂ and H₂O in the carrier and purge gas — both absorb strongly below ~180 nm; (2) window contamination — even a monolayer of pump oil, plasticiser, or fingerprint residue raises the cutoff dramatically; (3) lamp ageing — D₂ and Xe lamps lose deep-UV output before they lose visible output; (4) sample loading — overloaded peaks saturate the detector and broaden into the baseline.

Q: How should customers prepare samples for deep-UV GC-UV work?

Treat it like trace GC-MS, with two extra rules. First, eliminate water and oxygen from the sample path: dry solvents, low-bleed septa, and a fresh split liner before any deep-UV run. Second, control matrix loading — dilute heavy matrices so total mass on-column stays below ~100 ng per analyte. Use UV-grade carrier gas (≥99.9999% N₂ or He) with an in-line O₂/H₂O trap.

Question 1

Why does the site say “<155 nm” instead of an exact lower bound?

Accepted Answer

GC-UV detection extends well into the vacuum-UV, but the exact lower wavelength a given system reaches depends on the flow cell design, window material, carrier-gas purity, optical path length, and the absorbing species in the sample. Quoting a single fixed number would imply a guaranteed limit across all configurations and matrices, which isn't physically accurate. “<155 nm” communicates the meaningful capability — operation in the vacuum-UV — without overstating performance you can't reproduce in your own setup.

Question 2

What actually limits the lower wavelength?

Accepted Answer

Three things dominate: (1) absorption by the carrier gas itself (N₂ is largely transparent down to ~145 nm; O₂ and H₂O cut in much earlier), (2) the transmission cutoff of the flow-cell windows (MgF₂, LiF, and synthetic silica each have different deep-UV cutoffs), and (3) lamp emission and detector quantum efficiency at very short wavelengths. INSCAN is engineered so all three are pushed as far into the vacuum-UV as the application requires.

Question 3

Does GC-UV always operate at the lowest possible wavelength?

Accepted Answer

No — and it shouldn't. The optimal wavelength window is chosen per analyte. Many compound classes have their strongest, most selective absorption bands above 155 nm. Going lower buys you sensitivity for non-UV-active compounds and class-level fingerprints, but it isn't free: shorter wavelengths require stricter purge, cleaner gas, and shorter optical paths.

Question 4

How should I interpret the spec sheets?

Accepted Answer

Treat the published range (typ. <155–330 nm) as the envelope INSCAN can operate within. The wavelength range that's relevant to your method is a subset chosen during method development, based on your analytes, matrix, and required limits of detection. Our applications team confirms the working window during a feasibility scan.

Question 5

Is “<155 nm” a marketing hedge?

Accepted Answer

It's the opposite — it's the honest framing. A specific sub-155 nm number would only be defensible under one configuration with one sample. The “<155 nm” phrasing matches how peer-reviewed GC-UV literature describes vacuum-UV operation, and it's consistent with how spectroscopy vendors quote ranges (e.g. “below 200 nm” for deep-UV HPLC detectors).

Question 6

What does “far below 155 nm” actually mean in practice?

Accepted Answer

“Far below 155 nm” means the optical path is engineered to keep transmitting useful signal deep into the vacuum-UV — typically into the 130–150 nm region, and in some configurations approaching the LiF cutoff near 105 nm. In that regime almost every organic molecule has a strong σ→σ* or n→σ* absorption, so even compounds that look “UV-transparent” in conventional HPLC detectors (alkanes, fixed gases, simple halocarbons) become detectable with class-specific spectra.

Question 7

What limits performance at the deepest wavelengths?

Accepted Answer

Four things, in order of impact: (1) residual O₂ and H₂O in the carrier and purge gas — both absorb strongly below ~180 nm; (2) window contamination — even a monolayer of pump oil, plasticiser, or fingerprint residue raises the cutoff dramatically; (3) lamp ageing — D₂ and Xe lamps lose deep-UV output before they lose visible output; (4) sample loading — overloaded peaks saturate the detector and broaden into the baseline.

Question 8

How should customers prepare samples for deep-UV GC-UV work?

Accepted Answer

Treat it like trace GC-MS, with two extra rules. First, eliminate water and oxygen from the sample path: dry solvents, low-bleed septa, and a fresh split liner before any deep-UV run. Second, control matrix loading — dilute heavy matrices so total mass on-column stays below ~100 ng per analyte. Use UV-grade carrier gas (≥99.9999% N₂ or He) with an in-line O₂/H₂O trap.

Isomer differentiation (positional / structural) with GC-UV.

What this objective means

Why GC-UV fits

Typical matrices

Frequently asked questions

Can GC-UV distinguish m-xylene from p-xylene?

What about cis/trans olefin isomers?

How is this different from chiral GC?

Related publications

Related in Selectivity & resolution

Co-elution deconvolution

Spectral peak confirmation

Compound-class screening

Let's discuss your isomer differentiation (positional / structural) project.