Fused Silica vs Natural Quartz vs Borosilicate Capillary Tubes — Material Selection Guide
MachinedQuartz · Material Selection Guide
Fused Silica vs Quartz vs Borosilicate Capillary Tubes — Explained
Three materials, very different limits. Pick the wrong one and your UV measurements drift, your thermal application cracks the tube, or you overpay 5× for performance you don’t use. Decision flowchart, full spec table, and use-case lookup — all in 6 minutes.
3 materials compared
UV / temp / cost
Use-case lookup
Decision flowchart
📌 Note: This guide covers capillary tubes — long, narrow-bore quartz tubing used in HPLC, GC, and analytical instruments. If you’re looking for cuvettes (square optical sample cells for spectrophotometers), see our Cuvette Selection Guide instead. Capillary tubes don’t use the “Standard 80 / Sintered / Molded” fabrication grades — those terms only apply to assembled cuvettes.
Section 1
TL;DR — Which Material Fits You?
Quick Verdict
- Borosilicate glass — Cheapest. Use it for: visible-range chromatography, sample prep, GC injection ports below 500°C. Don’t use for: any UV work below 315 nm.
- Natural fused quartz — Mid-tier. Use it for: general UV-Vis spectroscopy (220–2500 nm), HPLC detection, GC at high temperatures (up to 1100°C). The default for most labs.
- Synthetic fused silica — Premium. Use it for: deep UV below 200 nm (pharma USP <857>, semiconductor analysis, photoresist quality control), thermal cycling beyond 1100°C, or trace contamination work.
⚡ Skip the technical details — Find your material by use case
| Your application | Recommended material |
|---|---|
| GC injection liner · visible-range only chromatography | Borosilicate (other vendors — we focus on quartz) |
| UV-Vis spectroscopy 220-800 nm · HPLC UV detector cells · routine lab use | Natural fused quartz ✓ view our SKUs → |
| High-temperature GC up to 1100°C · thermal applications | Natural fused quartz |
| Pharma method validation (USP <857>) · scans below 200 nm | Synthetic fused silica |
| Semiconductor processing · photoresist analysis · deep-UV laser systems | Synthetic fused silica |
| Trace metal analysis · ultra-pure chemistry · low contamination | Synthetic fused silica |
| Continuous use above 1100°C · thermal shock cycling | Synthetic fused silica |
| Routine GC septum injection at moderate temp | Borosilicate (other vendors) |
If your application isn’t listed, scroll to the decision flowchart in Section 5, or email us with your method.
Section 2
The Three Materials at a Glance
All three materials are silica-based (SiO₂), but they’re produced by very different processes — and those differences cascade into UV transmission, temperature limits, and price.
Tier 1 · Lowest cost
Borosilicate Glass
Composition: ~80% SiO₂ + boron oxide (B₂O₃). UV cutoff: ~315 nm — blocks deep UV. Max temp: 500°C continuous. Best use: chromatography, sample handling, visible spectroscopy. Cost: $5–15 per 100 cm tube.
Tier 2 · Workhorse
Natural Fused Quartz
Composition: 99.99% SiO₂ from electrically fused natural crystal. UV cutoff: ~220 nm. Max temp: 1100°C continuous, 1500°C short-term. Best use: general UV-Vis, HPLC, high-temp GC. Cost: $20–60 per 100 cm.
Tier 3 · Premium
Synthetic Fused Silica
Composition: 99.9999% SiO₂ from chemical vapor deposition. UV cutoff: ~170 nm — full deep UV. Max temp: 1200°C continuous. Best use: pharma USP, semiconductor, deep-UV laser systems. Cost: $80–200+ per 100 cm.
Section 3
UV Transmission: Where the Differences Are Critical
The single biggest difference between these three materials is where their UV cutoff sits. If your method uses any wavelength below 315 nm, borosilicate is out. Below 220 nm, only synthetic fused silica works.
Common method requirements (in order of UV demand):
- Protein A280 (280 nm): any of the three works, but borosilicate adds visible-range artifacts
- DNA A260 (260 nm): needs natural quartz or synthetic fused silica — borosilicate fails
- Trp/Tyr fluorescence excitation (220–280 nm): natural quartz minimum; synthetic fused silica preferred
- USP <857> method validation (200 nm): synthetic fused silica required for ≥83% transmission
- Photoresist analysis (190 nm): only synthetic fused silica
Section 4
Full Specification Comparison
| Property | Borosilicate Glass | Natural Fused Quartz | Synthetic Fused Silica |
|---|---|---|---|
| SiO₂ content | ~80% | 99.99% | 99.9999% |
| Production method | Soda-lime + B₂O₃ melt | Electrical fusion of natural crystal | Chemical vapor deposition (CVD) |
| UV cutoff (transmission >50%) | ~315 nm | ~220 nm | ~170 nm |
| Max continuous temperature | 500°C | 1100°C | 1200°C |
| Max short-term temperature | 515°C | 1500°C | 1500°C |
| Thermal expansion (× 10⁻⁶/K) | 3.3 | 0.55 | 0.55 |
| Thermal shock resistance | ~150°C ΔT | ~1000°C ΔT | ~1000°C ΔT |
| OH content (impurity) | — | ~30-200 ppm | 1-1000 ppm (controlled) |
| Trace metal contamination | High (Na, B) | Low | Ultra-low |
| Chemical resistance | Good (HF, hot alkali damage) | Excellent (no HF) | Excellent (no HF) |
| Typical cost (per 100 cm) | $5–15 | $20–60 | $80–200+ |
| Best for | Chromatography, sample prep | UV-Vis, HPLC, GC | Pharma, semiconductor, R&D |
Section 5
Quick Selection Flowchart
Section 6
Cost vs Performance — Don’t Overpay
Found Your Match?
Browse 50+ In-Stock Quartz Capillary SKUs
Standard bores 0.1–5 mm ID · custom dimensions on request · MOQ 5 pieces · ships in 3-5 business days from our US fab.
The price difference between these materials is large — synthetic fused silica costs 5-10× more than borosilicate. The key insight: most labs don’t need synthetic fused silica. Natural fused quartz handles 90% of UV-Vis work at one-third the cost.
When synthetic fused silica is genuinely worth the premium:
- Regulatory compliance — USP <857> / Ph. Eur. 2.2.25 require ≥83% T at 200 nm; only synthetic grade clears this
- Trace contamination matters — semiconductor wafer cleaning, ultra-pure chemistry, single-cell biology
- Wavelengths below 200 nm — vacuum UV applications, photoresist analysis
- Continuous operation above 1100°C — most natural fused quartz tubes will deform; synthetic FS holds shape
For everything else — including most HPLC detectors, GC ovens, sample injection systems — natural fused quartz is the right call. If a vendor pushes synthetic fused silica without one of the four reasons above, ask why.
💡 Real Cost Savings
MachinedQuartz natural fused quartz capillary tubes match Hellma and Starna optical specs at 30-50% lower cost and ship in 3-5 days from our US fab. Same UV cutoff (220 nm), same temperature ratings (1100°C), same chemical resistance — without the European import lead time. Browse our catalog →
Section 7
Frequently Asked Questions
Can I substitute natural fused quartz for synthetic fused silica?
For wavelengths above 220 nm and temperatures up to 1100°C, yes — they’re functionally equivalent at one-third the cost. For deep UV (below 220 nm), pharma USP method validation, or trace metal analysis, no — you need synthetic. The difference is purity and OH content, both of which affect deep-UV transmission and contamination.
What’s the UV cutoff difference between natural and synthetic fused silica?
Natural fused quartz cuts off around 220 nm. Synthetic fused silica extends down to ~170 nm — a 50 nm advantage in the deep UV. For most lab work this doesn’t matter. For protein analysis at 200 nm, USP method validation, or photoresist applications, the difference is critical.
Will any quartz capillary handle HF?
No. HF dissolves SiO₂ at any concentration regardless of grade or production method. SiO₂ + 6HF → H₂SiF₆ + 2H₂O is irreversible. For HF applications, switch to PTFE or PFA capillaries (sold by Hamilton, IDEX, and other lab suppliers). The HF/quartz incompatibility comes from the SiO₂ chemistry itself — it applies to any quartz product, not just capillary tubes.
What’s the price difference, roughly?
For a 100 cm tube of standard bore: borosilicate $5–15, natural fused quartz $20–60, synthetic fused silica $80–200+. The premium for synthetic comes from CVD production and tighter QC on impurities. For specific quotes including custom bore sizes, see our quartz capillary catalog.
Can I use borosilicate for HPLC?
For sample injection or fittings — yes. For the UV detector flow cell — usually not, because most HPLC UV detectors scan into the 200–280 nm range where borosilicate cuts off. Use natural fused quartz for the detection path; borosilicate is fine for non-optical components.
Why doesn’t MachinedQuartz sell borosilicate capillary tubes?
We focus on UV-grade applications where natural fused quartz and synthetic fused silica perform best — protein A280, HPLC UV detection, pharma USP methods, semiconductor processes. Borosilicate is a perfectly fine material for visible-range chromatography and GC liners, but those markets are well-served by other vendors (Restek, Hamilton, Agilent). If you only need borosilicate, we’d rather direct you to those suppliers than sell you a product outside our specialty. If you need any UV-grade quartz capillary, we’re a strong fit — see our catalog.
How long do these capillary tubes last?
All three materials, used within their temperature and chemical limits, can last 5–10 years of regular use. Lifetime is usually limited by mechanical handling (chips, scratches) rather than material degradation. Synthetic fused silica tubes used at high temperatures may slowly devitrify (form cristobalite crystals) after thousands of hours — this isn’t a chemistry failure but a structural one.