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.

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.

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.

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.

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).

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.

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.

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.

What does GC-VUV stand for?

GC-VUV stands for Gas Chromatography with Vacuum Ultraviolet detection. The 'vacuum' refers to the wavelength region (roughly 125–200 nm) that is absorbed by atmospheric gases and therefore historically required a vacuum-purged optical path.

Commercial GC-VUV was pioneered by VUV Analytics, a Texas-based instrument company spun out of the University of Texas at Austin in 2011. The underlying physics of vacuum-UV absorbance has been studied since the 1930s.

How does GC-VUV differ from GC-MS?

GC-MS ionises analytes and reports mass-to-charge ratios; GC-VUV records the molecule's absolute absorbance spectrum across roughly 125–240 nm. Spectra are non-destructive, follow Beer–Lambert (so quantitation is absolute), and are highly sensitive to structural and positional isomers — areas where electron-impact MS often struggles.

Is GC-VUV the same as GC-UV?

No. GC-UV (gas chromatography with ultraviolet detection, as deployed in INSCAN) operates in the deep-UV range without requiring a vacuum-purged optical path or helium carrier. GC-VUV operates in the vacuum-UV region (~125–200 nm) and requires both. Both share Beer–Lambert quantitation, but capex, running cost and throughput differ significantly.

What are the limitations of GC-VUV?

GC-VUV requires a continuously vacuum-purged optical path, high-purity helium carrier, and a relatively expensive deuterium VUV source. This raises capex, running cost and maintenance complexity compared with conventional GC-UV. The 125–200 nm region also carries less compound-specific structural detail than the 200–330 nm region for many aromatic and heteroaromatic analytes.

Technique Explainer

GC-VUV: Vacuum Ultraviolet Gas Chromatography

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.

Gas chromatography with vacuum ultraviolet detection — usually shortened to GC-VUV — couples a standard gas chromatograph to a deuterium-lamp spectrometer that records absorbance from roughly 125 to 240 nanometres. Almost every gas-phase organic and inorganic molecule absorbs somewhere in that window, which makes GC-VUV one of the most universal absorbance-based detectors ever commercialised. This page is a neutral, technical primer: where the technique came from, how it works, what it does well, where it struggles, and how it relates to the broader gas-chromatography detector landscape — including conventional GC-UV, GC-MS, and GC-FTIR.

A short history of GC-VUV

Vacuum-UV spectroscopy itself dates to the 1930s, but coupling it to gas chromatography was impractical for decades because the sub-200 nm region is absorbed by atmospheric oxygen and water vapour. Commercial GC-VUV only arrived in 2014, when VUV Analytics (Austin, Texas, USA) released the first benchtop instrument based on research from the University of Texas at Austin. Their VGA-100 detector and successors brought vacuum-UV absorbance into mainstream petrochemical and pharmaceutical labs, most notably for PIONA (paraffin / iso-paraffin / olefin / naphthene / aromatic) hydrocarbon classification under ASTM D8071.

How GC-VUV works

A GC-VUV detector sits at the end of a conventional capillary GC column. The column effluent enters a heated flow-cell illuminated by a deuterium lamp emitting a continuum from roughly 115 nm upward. A diffraction grating disperses the transmitted light onto a detector array, producing a complete absorbance spectrum every 50–100 milliseconds. Because the analytes follow the Beer–Lambert law in the gas phase, concentration is recovered directly from cross-section libraries — no response factor, no internal standard, no surrogate calibration. The entire optical path must be continuously purged, usually with high-purity nitrogen, to keep oxygen and water from re-absorbing the vacuum-UV photons.

Strengths of GC-VUV

Universal response. Almost every organic molecule absorbs in 125–240 nm, including saturated hydrocarbons that are nearly invisible to conventional UV.
Absolute quantitation. Beer–Lambert quantitation removes the need for compound-specific response factors.
Co-elution deconvolution. Overlapping peaks can be mathematically resolved when their reference spectra are linearly independent.
Isomer discrimination. Positional isomers (ortho-, meta-, para-xylene; cis/trans alkenes) often have visibly distinct VUV spectra where mass spectra are nearly identical.
Non-destructive. The detector does not consume the analyte, allowing serial coupling to MS or FID.

Limitations of GC-VUV

Vacuum / purge requirement. Continuous nitrogen purge of the optical path adds operating cost and a single point of failure.
Helium carrier preference. Most validated methods rely on high-purity helium, exposing labs to global helium supply volatility.
Capex. A deuterium VUV source plus vacuum-tolerant optics make GC-VUV detectors substantially more expensive than FID, ECD or conventional GC-UV.
Limited structural detail above 200 nm. Many aromatic, heteroaromatic and conjugated systems carry their richest fingerprint information in the 200–330 nm band — a region GC-VUV instruments don't always cover at full resolution.
Service ecosystem. The VUV detector market is concentrated around a single vendor, which complicates spare-parts logistics outside North America.

Typical GC-VUV applications

PIONA hydrocarbon classification (ASTM D8071) for gasoline and naphtha.
Permanent gas analysis (CO, CO₂, CH₄, N₂O, light hydrocarbons).
Terpene profiling in cannabis, hops and essential oils.
Fatty-acid methyl-ester (FAME) speciation in biofuels.
Forensic accelerant identification and arson-debris analysis.
Pharmaceutical residual-solvent screens where ICH Q3C compounds need positive identification beyond retention time.

How GC-UV compares to GC-VUV

Conventional GC-UV — the technique behind Labio's INSCAN platform — operates in the deep-ultraviolet region above 155 nm and does not require a vacuum-purged optical path or helium carrier. The trade-off is straightforward: GC-VUV captures more of the very-short-wavelength fingerprint, while GC-UV is dramatically cheaper to acquire and run, supports nitrogen or hydrogen carriers, and reaches isomer-level identification across most petrochemical and pharmaceutical analytes. For a side-by-side breakdown of vacuum requirements, wavelength range, capex and application fit, see our dedicated GC-VUV vs GC-UV comparison. If you are actively evaluating an alternative to a GC-VUV detector, our GC-VUV alternative page walks through the typical migration path.

Frequently asked questions about GC-VUV

What does GC-VUV stand for?: GC-VUV stands for Gas Chromatography with Vacuum Ultraviolet detection. The 'vacuum' refers to the wavelength region (roughly 125–200 nm) that is absorbed by atmospheric gases and therefore historically required a vacuum-purged optical path.
Who invented GC-VUV?: Commercial GC-VUV was pioneered by VUV Analytics, a Texas-based instrument company spun out of the University of Texas at Austin in 2011. The underlying physics of vacuum-UV absorbance has been studied since the 1930s.
How does GC-VUV differ from GC-MS?: GC-MS ionises analytes and reports mass-to-charge ratios; GC-VUV records the molecule's absolute absorbance spectrum across roughly 125–240 nm. Spectra are non-destructive, follow Beer–Lambert (so quantitation is absolute), and are highly sensitive to structural and positional isomers — areas where electron-impact MS often struggles.
Is GC-VUV the same as GC-UV?: No. GC-UV (gas chromatography with ultraviolet detection, as deployed in INSCAN) operates in the deep-UV range without requiring a vacuum-purged optical path or helium carrier. GC-VUV operates in the vacuum-UV region (~125–200 nm) and requires both. Both share Beer–Lambert quantitation, but capex, running cost and throughput differ significantly.
What are the limitations of GC-VUV?: GC-VUV requires a continuously vacuum-purged optical path, high-purity helium carrier, and a relatively expensive deuterium VUV source. This raises capex, running cost and maintenance complexity compared with conventional GC-UV. The 125–200 nm region also carries less compound-specific structural detail than the 200–330 nm region for many aromatic and heteroaromatic analytes.

Compare GC-VUV with INSCAN's GC-UV detector.

GC-VUV vs GC-UV