Borosilicate Capillary Tubes: Performance, Specifications, and How to Apply It in Industry

Types of Borosilicate Capillary Tubes

Borosilicate capillary tubes are essential components in scientific research, medical diagnostics, and industrial applications due to their exceptional thermal resistance, chemical inertness, and optical clarity. Made from borosilicate glass—which contains boron trioxide—these tubes can withstand extreme temperature fluctuations and corrosive substances, making them ideal for precision laboratory work. Depending on the experimental requirements, various specialized types of capillary tubes are available, each designed to meet specific performance criteria such as sample integrity, durability, and measurement accuracy.

Filled Capillary Tubes

Pre-loaded with a liquid or solid substance (e.g., blood, dyes, reagents), these tubes provide ready-to-use samples for immediate analysis.

Advantages

• Enable instant measurements with direct readings
• Reduce preparation time in clinical and lab settings
• Minimize risk of contamination (sealed design)
• Ideal for standardized diagnostic tests

Limitations

• Limited to pre-determined substances
• Less flexibility for custom experimentation
• Require proper storage to maintain stability

Best for: Medical diagnostics, hematology, point-of-care testing, calibration standards

Unfilled Capillary Tubes

Empty tubes designed for user-filled applications, offering maximum versatility in experimental setups.

Advantages

• Highly adaptable for diverse liquids and gases
• Used in gas chromatography with stationary phases
• Essential in thermal expansion instruments (e.g., dilatometers, thermometers)
• Support precise volume control and capillary action studies

Limitations

• Require careful handling during filling
• Potential for air bubbles or contamination
• Need additional preparation steps before use

Best for: Research labs, chromatography, physical property measurement, educational experiments

Heat-Treated Capillary Tubes

Subjected to controlled thermal processing to enhance mechanical strength and resistance to thermal shock.

Advantages

• Superior resistance to cracking under rapid temperature changes
• Extended service life in high-stress environments
• Maintain dimensional stability at elevated temperatures
• Critical for applications involving heating or cooling cycles

Limitations

• Higher manufacturing cost
• May require specialized suppliers
• Slight reduction in optical clarity in some cases

Best for: Metallurgy, materials science, high-temperature reactors, thermal cycling experiments

Sealed Capillary Tubes

Hermetically closed after sample insertion, protecting contents from air, moisture, and contamination.

Advantages

• Long-term sample preservation
• Prevent evaporation and oxidation of sensitive materials
• Used in reference standards and archival storage
• Ensure safety when handling hazardous or volatile substances

Limitations

• Single-use in most cases
• Cannot be refilled or modified post-sealing
• Require precise sealing techniques

Best for: Chemistry, biology, pharmaceuticals, calibration fluids, mercury thermometers

Fused Capillary Tubes

Manufactured by melting and bonding two or more glass sections into a seamless, unified structure.

Advantages

• Exceptional structural integrity and strength
• No weak joints or potential leak points
• High precision in inner diameter consistency
• Ideal for long-duration and high-pressure applications

Limitations

• More complex and costly production process
• Limited availability compared to standard tubes
• Custom fabrication may increase lead time

Best for: Physicochemical research, microfluidics, laser systems, high-precision instrumentation

Type	Durability	Application Flexibility	Thermal Resistance	Primary Use Cases
Filled Capillary Tubes	Medium	Low	Good	Medical diagnostics, blood testing, calibration
Unfilled Capillary Tubes	Medium	Excellent	Good	Chromatography, thermometers, research experiments
Heat-Treated Capillary Tubes	Excellent	Good	Exceptional	High-temperature testing, materials analysis
Sealed Capillary Tubes	Very Good	Fair	Very Good	Sample storage, reactive chemicals, thermometers
Fused Capillary Tubes	Excellent	Good	Excellent	Microfluidics, precision instruments, laser optics

Expert Tip: When using sealed or filled capillary tubes for temperature-sensitive applications, ensure they are gradually heated or cooled to avoid thermal stress fractures. Always follow manufacturer guidelines for maximum operating temperatures and handling procedures.

Specifications & Maintenance of Borosilicate Capillary Tubes

Borosilicate capillary tubes are essential components in scientific, medical, and industrial applications due to their excellent thermal resistance, chemical durability, and optical clarity. When sourcing these precision glass tubes, understanding key specifications ensures compatibility with your experimental or operational requirements. Equally important is proper maintenance to preserve functionality, accuracy, and safety over time.

Key Specifications to Consider

Inner Diameter

The inner diameter (ID) of a borosilicate capillary tube directly affects fluid dynamics, sample volume, and application suitability. Tubes with inner diameters below 1 mm are ideal for microfluidic systems, microsurgery, and drug delivery applications where precise control over tiny liquid volumes is critical. These ultra-narrow bores minimize sample usage and enhance capillary action.

For general laboratory use—such as in thermometers, gas chromatography, or blood collection—capillary tubes with IDs between 1 mm and 2 mm are most common. They offer a balance between flow rate and precision. Larger diameters (above 2 mm) facilitate faster fluid movement and are easier to handle, making them suitable for applications requiring rapid sample transfer or higher throughput.

Length

Capillary tubes are manufactured in a wide range of lengths, from just a few centimeters to several meters, depending on the intended use. Shorter tubes (5–15 cm) are often used in compact analytical devices, portable diagnostic tools, or microfluidic chips where space constraints are critical.

Longer capillaries (up to 1–3 meters) are typically employed in high-performance liquid chromatography (HPLC), capillary electrophoresis, and fluid dynamics research, where extended path lengths improve separation efficiency and data resolution. Most standard applications utilize tubes between 10 cm and 1 m, which can be custom-cut to size using proper glass-cutting techniques without compromising structural integrity.

Wall Thickness

Wall thickness significantly influences the mechanical strength, flexibility, and thermal performance of borosilicate capillary tubes. Thicker-walled tubes (0.5–1 mm) provide enhanced durability and resistance to pressure fluctuations, making them suitable for high-pressure systems, autoclaving, or environments involving mechanical stress.

Thinner-walled tubes (0.2–0.4 mm) reduce overall weight and material usage, which is advantageous in sensitive instrumentation or miniaturized devices. While more fragile, they allow for greater precision in applications where minimal dead volume and reduced inertia are important. The typical wall thickness range for most borosilicate capillaries is 0.2 mm to 1 mm, offering a versatile balance of strength and functionality.

Material Quality & Purity

Borosilicate glass (e.g., Type 3.3 or equivalent) is preferred for capillary tubes due to its low coefficient of thermal expansion, high resistance to thermal shock, and exceptional chemical inertness. High-purity borosilicate formulations minimize leaching of ions into sensitive samples, ensuring accurate results in analytical and biological applications.

Look for tubes made from optical-grade or pharmaceutical-grade borosilicate glass when working with sensitive assays, spectroscopy, or sterile environments. Surface treatments such as silanization or coating with hydrophobic/hydrophilic layers may also be available to modify wetting behavior for specialized applications like capillary electrophoresis or microreactors.

Specification	Typical Range	Recommended Applications
Inner Diameter	0.1 mm – 3 mm	Microfluidics (<1 mm), Chromatography (1–2 mm), Sample Transfer (>2 mm)
Length	5 cm – 3 m	Miniature Devices (5–15 cm), Analytical Systems (10 cm – 1 m), Extended Separations (1–3 m)
Wall Thickness	0.2 mm – 1 mm	Fragile Systems (0.2–0.4 mm), High-Pressure Use (0.5–1 mm)
Thermal Resistance	Up to 500°C (short-term)	Heat-resistant applications; avoid rapid thermal cycling

Essential Maintenance Practices

Cleaning Protocol: Residue buildup can alter surface tension, block flow, or contaminate samples. After each use, flush capillary tubes with an appropriate solvent—acetone or ethanol for organic residues, diluted nitric acid for metal ions, or enzymatic cleaners for biological materials. Rinse thoroughly with deionized water and dry using filtered air or nitrogen to prevent particle deposition.

Storage Guidelines: Store capillary tubes horizontally in protective sleeves, padded trays, or dedicated storage boxes to prevent breakage. Keep them in a clean, dry environment free from dust, moisture, and corrosive fumes. Label containers clearly to avoid mix-ups, especially when multiple sizes or treated tubes are in use.

Pre-Use Inspection: Always inspect tubes under bright light or magnification before use. Check for microcracks, chips, or internal deposits that could compromise performance. Even minor defects can lead to catastrophic failure under pressure or during heating. Discard any damaged tubes immediately to maintain experimental integrity and user safety.

Temperature Management: Although borosilicate glass resists thermal shock better than soda-lime glass, sudden temperature changes (thermal shock) can still cause cracking. Always heat or cool capillary tubes gradually. When using open flames (e.g., Bunsen burners), rotate the tube evenly to distribute heat uniformly and avoid localized stress points.

Handling & Safety: Use gloves and eye protection when handling glass capillaries to prevent injury from sharp edges. Avoid excessive bending or force during installation. For applications involving high pressure or vacuum, ensure compatibility with connectors and fittings to prevent leaks or implosions.

Important: Never reuse capillary tubes in sterile or highly sensitive applications without validated cleaning and sterilization procedures. Improper cleaning can lead to cross-contamination, inaccurate readings, or equipment damage. Always follow manufacturer guidelines and laboratory protocols to ensure optimal performance and compliance with quality standards.

Applications of Borosilicate Capillary Tubes Across Industries

Borosilicate capillary tubes are essential components in scientific and industrial applications due to their exceptional thermal stability, chemical resistance, and optical clarity. Made from borosilicate glass—a material composed primarily of silica and boron trioxide—these tubes can withstand rapid temperature changes, resist corrosion from most chemicals, and maintain structural integrity under demanding conditions. Their precise dimensions and inert nature make them ideal for handling sensitive samples, accurate measurements, and controlled processes across diverse fields. Below is a comprehensive overview of their critical roles in research, medical, industrial, agricultural, and veterinary settings.

Research Laboratories

Borosilicate capillary tubes are a staple in modern research laboratories, where precision, durability, and reliability are paramount. Their high resistance to thermal shock (typically withstanding temperatures up to 500°C) allows them to be used in experiments involving extreme heat, such as flame tests, distillation processes, and high-temperature reactions.

• Used in gas chromatography and capillary electrophoresis for precise sample introduction and separation
• Ideal for micro-volume liquid handling in analytical chemistry, enabling accurate dispensing of microliter quantities
• Employed in physics experiments to control and measure small gas volumes under variable pressure and temperature
• Frequently used in spectroscopy due to their optical transparency and minimal interference with light transmission

Key advantage: Their inert surface prevents unwanted chemical interactions, preserving sample integrity during sensitive experiments.

Medical Laboratories

In clinical and diagnostic environments, borosilicate capillary tubes play a vital role in patient care and medical testing. Their high purity and ability to maintain sterility make them indispensable for handling biological specimens without contamination.

• Widely used in hematocrit testing and blood gas analysis, where small blood samples (as little as 10–50 µL) are collected via capillary action
• Essential in point-of-care testing devices, enabling rapid diagnostics with minimal invasiveness
• Used in microfluidic systems for drug delivery research and lab-on-a-chip technologies
• Compatible with autoclaving and gamma irradiation, ensuring full sterilization for sterile medical applications

Patient benefit: Minimally invasive sampling reduces discomfort and enables frequent monitoring, especially in pediatric and geriatric populations.

Industrial Applications

Beyond the lab, borosilicate capillary tubes are integral to various industrial processes that demand precision, durability, and resistance to harsh environments. Their ability to function reliably under high pressure, extreme temperatures, and corrosive conditions makes them suitable for advanced manufacturing and process control systems.

• Used in precision thermometers and temperature sensors, particularly in oil refineries, chemical plants, and power generation facilities
• Applied in viscometers to measure the flow characteristics of heavy oils, polymers, and other viscous industrial fluids
• Utilized in material science for studying thermal expansion, phase transitions, and sintering behaviors of metals and ceramics
• Integrated into optical sensors and fiber optics due to their excellent light transmission and mechanical stability

Engineering advantage: Long-term stability under cyclic thermal stress ensures consistent performance in continuous industrial operations.

Agriculture & Veterinary Science

In agricultural research and veterinary medicine, borosilicate capillary tubes support innovation in animal health, crop development, and biotechnology. Their robustness and compatibility with biological materials make them ideal for field and laboratory use alike.

• Used for micro-sampling of serum, plasma, and tissue fluids in livestock health monitoring and disease diagnosis
• Employed in artificial insemination and embryo transfer procedures requiring precise fluid handling
• Critical in plant biotechnology for microinjection of genetic material into plant cells or insect vectors
• Used in pesticide residue testing and soil nutrient analysis through capillary-based micro-extraction techniques

Field-ready feature: Resistant to breakage and easy to sterilize, making them reliable tools in mobile clinics and remote research stations.

Best Practice Tip: When selecting borosilicate capillary tubes, ensure they meet international standards (e.g., ISO 759, ASTM E237) for dimensional accuracy and material composition. For medical and food-related applications, verify compliance with USP Class VI or FDA guidelines to guarantee biocompatibility and safety.

Application Area	Key Use Case	Material Advantage	Typical Dimensions
Research Labs	Micro-volume analysis, electrophoresis	Chemical inertness, thermal stability	0.5–2 mm diameter, 50–150 mm length
Medical Diagnostics	Blood sampling, hematocrit testing	Sterilizability, optical clarity	1–1.5 mm diameter, 75–100 mm length
Industrial Sensing	Temperature probes, viscosity measurement	Pressure resistance, durability	1–3 mm diameter, 100–300 mm length
Agriculture/Veterinary	Microinjection, serum sampling	Break resistance, biocompatibility	0.8–2 mm diameter, 50–120 mm length

Additional Considerations for Optimal Use

• Surface Treatment: Some capillary tubes feature hydrophilic or hydrophobic coatings to enhance fluid control and prevent sample adhesion
• Customization: Available in various lengths, diameters, and tip configurations (e.g., sealed, flared, or tapered) for specialized applications
• Storage: Should be kept in clean, dry environments to prevent contamination or moisture absorption
• Handling: Use gloves to avoid oil transfer from skin, which can affect capillary action and sample purity
• Sustainability: Fully recyclable and reusable after proper cleaning, supporting eco-friendly lab practices

Key Factors to Consider When Choosing a Supplier of Borosilicate Capillary Tubes

Selecting the right supplier for borosilicate capillary tubes is crucial for laboratories, research institutions, and industrial operations that rely on precision glassware for accurate measurements and experiments. These specialized tubes are widely used in analytical instruments, medical devices, and scientific research due to their excellent thermal resistance, chemical durability, and optical clarity. To ensure consistent performance and reliability, it’s essential to evaluate suppliers based on several critical factors. This guide outlines the most important considerations to help you make an informed decision and establish a long-term, trustworthy partnership.

Important Note: Borosilicate capillary tubes are often used in sensitive applications such as chromatography, microfluidics, and spectroscopy. Even minor defects or dimensional inconsistencies can compromise experimental accuracy. Therefore, supplier selection should prioritize quality, consistency, and technical support over cost alone.

1. Quality Control and Manufacturing Standards

The performance of borosilicate capillary tubes in scientific and industrial applications depends heavily on manufacturing precision and material integrity. High-quality tubes must be produced using premium-grade borosilicate glass (such as Schott 8250 or equivalent) to ensure low thermal expansion, high resistance to thermal shock, and minimal chemical leaching.

Suppliers should implement rigorous quality control (QC) processes throughout production, including:

• Raw material verification and batch traceability
• Automated dimensional inspection (inner/outer diameter, wall thickness, length)
• Visual and microscopic examination for bubbles, striations, or surface imperfections
• Compliance with international standards such as ISO 9001 for quality management
• Certifications like USP Class VI or FDA compliance for medical or pharmaceutical applications

Ask potential suppliers for quality documentation, including Certificates of Conformance (CoC), test reports, and process validation data. A transparent QC process reflects a supplier’s commitment to delivering reliable, high-performance products.

Expert Tip: Request sample batches before placing large orders. Testing the samples in your actual application environment can reveal subtle differences in quality, consistency, and compatibility that are not apparent from specifications alone.

2. Range of Products and Customization Capabilities

Borosilicate capillary tubes are available in a wide variety of dimensions and configurations to suit different applications. Common outer diameters range from 0.5 mm to 5.0 mm, with inner diameters varying from 0.1 mm to 3.0 mm, and lengths from a few centimeters to over a meter. Wall thickness, tip configurations (e.g., sealed, tapered, or open-ended), and surface treatments (e.g., silanization) may also vary.

An ideal supplier should offer:

• A comprehensive catalog covering standard sizes and specifications
• Custom manufacturing options for non-standard dimensions or specialized features
• Value-added services such as cutting, polishing, bending, or laser marking
• Compatibility with common instrumentation (e.g., GC, HPLC, CE systems)

Partnering with a supplier that provides a broad product range and customization options allows labs to consolidate procurement, reduce lead times, and streamline inventory management. It also ensures access to specialized solutions for unique research or production needs.

Product Feature	Common Specifications	Customization Options	Typical Applications
Outer Diameter	0.5 – 5.0 mm	Custom ODs available upon request	Microfluidics, sensors, optical fibers
Inner Diameter	0.1 – 3.0 mm	Precision drilling for narrow bores	Chromatography, capillary electrophoresis
Length	50 mm – 1000 mm	Cut-to-length service available	Laboratory analysis, medical devices
Wall Thickness	0.1 – 1.5 mm	Controlled for burst pressure requirements	High-pressure systems, reactors
End Treatment	Open, sealed, or flared ends	Tapered, rounded, or laser-sealed tips	Sample injection, micro-pipetting

3. Pricing Structure and Minimum Order Quantities (MOQs)

Cost is a significant factor, especially for small laboratories, startups, or academic institutions with limited budgets. However, the lowest price should not come at the expense of quality. It's important to compare pricing across multiple suppliers while considering the total value, including product consistency, technical support, and delivery reliability.

Pay close attention to:

• Minimum Order Quantities (MOQs): Some suppliers require large MOQs (e.g., 1,000+ units), which may not be feasible for smaller buyers. Look for suppliers that offer flexible MOQs or sample pricing for evaluation.
• Volume Discounts: Inquire about tiered pricing based on order volume, which can lead to long-term savings.
• Hidden Costs: Clarify shipping, packaging, and handling fees, especially for international orders.
• Payment Terms: Suppliers offering net-30 or extended payment terms can improve cash flow for businesses.

Building a strong relationship with a supplier can lead to more favorable pricing, reduced MOQs, and priority handling—especially if you demonstrate potential for recurring orders.

4. Industry Experience and Supplier Reputation

A supplier’s track record in the scientific glassware or laboratory equipment industry is a strong indicator of reliability and expertise. Long-established suppliers often have:

• Proven manufacturing capabilities and access to high-quality raw materials
• Deep understanding of application-specific requirements
• Established quality systems and experienced technical staff
• Strong relationships with OEMs and research institutions

To assess a supplier’s reputation:

• Review customer testimonials and case studies on their website
• Check third-party review platforms or industry forums
• Ask for references from existing clients in similar fields
• Evaluate responsiveness and technical knowledge during initial inquiries
• Verify certifications and compliance with regulatory standards

A reputable supplier should not only deliver high-quality products but also provide excellent customer service, technical support, and timely delivery—key components of a successful long-term partnership.

Pro Tip: Attend industry trade shows or webinars to meet suppliers in person, examine product samples, and gain insights into their manufacturing processes and innovation capabilities.

Final Recommendations

• Always request product samples before committing to large orders
• Prioritize suppliers with transparent quality control and documentation
• Choose a supplier that offers both standard and custom solutions
• Negotiate flexible terms, especially if you're a small or medium-sized buyer
• Establish a long-term relationship with a reliable partner to ensure supply chain stability

Selecting the right borosilicate capillary tube supplier is an investment in the accuracy, efficiency, and success of your scientific or industrial operations. By carefully evaluating quality, product range, pricing, and reputation, you can identify a partner that meets your current needs and supports your future growth.

Frequently Asked Questions About Borosilicate Capillary Tubes

Q1: What are borosilicate capillary tubes used for?

Borosilicate capillary tubes are essential components in various scientific, medical, and industrial applications due to their unique combination of thermal stability, chemical resistance, and optical clarity. Their primary uses include:

• Medical Diagnostics: Widely used in blood collection and hematocrit testing, where only a small volume of blood is required. Their narrow bore allows precise handling of micro-samples, making them ideal for finger-prick tests and capillary blood sampling.
• Laboratory Analysis: Employed in fluid measurement, gas control, and temperature-sensitive experiments. Their inert nature ensures minimal interference with chemical reactions or sample integrity.
• Chromatography: Critical in techniques like gas chromatography (GC) and capillary electrophoresis (CE), where they serve as separation columns. Their uniform internal diameter enables high-resolution analysis of complex mixtures.
• Material Science: Used to study phase transitions, viscosity, and thermal expansion under controlled conditions due to their ability to withstand rapid temperature changes.
• Microfluidics: Integrated into lab-on-a-chip devices for manipulating tiny fluid volumes in research and diagnostics.

Thanks to their durability and resistance to thermal shock and corrosive substances, borosilicate capillary tubes outperform standard glass in demanding environments, making them a preferred choice across disciplines.

Q2: Are capillary tubes flexible?

Borosilicate glass capillary tubes are rigid by nature and exhibit very limited flexibility. While they are stronger and more thermally stable than ordinary soda-lime glass, they remain inherently brittle and cannot be bent significantly without risk of fracture.

• Mechanical Behavior: These tubes can withstand slight flexing under controlled conditions, but any sharp bending or lateral pressure may cause cracking or complete breakage.
• Comparison to Other Materials: Unlike flexible polymers (e.g., PTFE or silicone tubing) or metal capillaries, borosilicate glass does not deform elastically. It maintains its shape under normal use but lacks shock absorption.
• Handling Precautions: To prevent damage, avoid applying uneven force, dropping, or clamping too tightly. Always use appropriate holders or mounts when integrating into instruments.

Although their rigidity ensures dimensional stability and precision in applications like chromatography, it also means that careful handling and proper installation are crucial to avoid breakage and ensure longevity.

Q3: How do you fix a broken capillary tube?

Unfortunately, a broken borosilicate capillary tube cannot be effectively repaired and must be replaced. Here’s why:

• Structural Integrity: Even if the pieces are perfectly aligned and fused using high-temperature flame sealing, the resulting joint will be weaker than the original tube and prone to failure under pressure or thermal cycling.
• Internal Diameter Disruption: Any repair attempt risks altering the uniform internal bore, which is critical for accurate fluid flow, separation efficiency, or sample volume measurement.
• Contamination Risk: The repair process can introduce impurities or micro-cracks that compromise the tube’s performance, especially in sensitive analytical applications.
• Sealing Challenges: Achieving an airtight, leak-free seal after breakage is extremely difficult without specialized equipment and often results in inconsistent outcomes.

To minimize breakage, always source high-quality capillary tubes from reputable suppliers and follow best practices for storage and handling. Using protective sleeves or enclosures during operation can also reduce the risk of accidental damage.

Q4: How do you sterilize a capillary tube?

Sterilization of borosilicate capillary tubes is vital in medical, biological, and analytical applications to prevent contamination. Several effective methods are available, each suited to specific needs:

Sterilization Method	Process	Advantages	Considerations
Chemical Disinfection	Soaking in ethanol, isopropanol, or bleach solutions (e.g., 70% alcohol for 15–30 minutes).	Simple, fast, and suitable for heat-sensitive setups.	May leave residues; requires thorough rinsing with sterile water or air drying.
Autoclaving	Exposure to pressurized steam (121°C at 15 psi for 15–20 minutes).	Kills all microorganisms, including spores; highly reliable.	Ensure tubes are uncapped and properly positioned to allow steam penetration; avoid thermal shock.
Dry Heat Sterilization	Heating in an oven at 160–180°C for 1–2 hours.	No moisture involved; ideal for instruments that can’t tolerate steam.	Energy-intensive; longer cycle time; ensure even heating to prevent cracking.

Before sterilization, clean the tubes with appropriate solvents to remove organic or particulate matter. After treatment, store in a clean, dust-free environment. Always verify compatibility with your specific application—especially in analytical systems where trace contaminants can affect results.