Glass Capillary Tube Selection Core: Size Determines Function, Material Determines Performance, Application Scenario Determines Everything

Glass capillary tubes may seem simple, but choosing the wrong specifications can lead to experimental failure, inaccurate data, or reduced production efficiency. This guide reveals the five golden rules for selecting glass capillary tubes.

Step 1: Define Your Application Scenario

Different fields have vastly different requirements:

Medical & Clinical Field

• Hematocrit Determination: Requires standard 75mm length, heparinized tubes with ~1.1-1.2mm inner diameter

• Micro Blood Collection: Thin-walled tubes with 0.5-0.8mm ID to minimize patient discomfort

• Blood Glucose Sampling: Ultra-fine capillaries (<0.5mm ID) enable microliter-level sampling

Laboratory & Research

• Microinjection/Patch Clamp: Borosilicate glass, customizable tip diameter to 0.5μm

• Gas Chromatography: Fused silica tubes with 0.25-0.53mm ID

• Surface Tension Measurement: High-precision uniform ID required, tolerance < ±2%

Industrial Applications

• Level Gauges: Thick-walled reinforced type, pressure and corrosion resistant

• Adhesive Dispensing: Silanized hydrophobic inner wall to prevent adhesive adhesion
  

Core Parameters: Four Key Specifications

1. Dimensional Parameters: Precision Determines Success

Pro Tip: Use Q = (πr⁴ΔP)/(8ηL) to estimate flow rate (r=radius, ΔP=pressure diff, η=viscosity, L=length)

2. Glass Material: Chemical Compatibility is Critical

Borosilicate Glass (Recommended for most applications)

• Temperature Range: -80°C to +500°C

• Thermal Expansion: 3.3×10⁻⁶/K

• Chemical Resistance: Acids, bases, organic solvents

• Brands: Pyrex®, Duran®, Simax®

Fused Quartz (High-end special applications)

• Temperature Range: -200°C to +1100°C

• UV Transmittance >90%

• Cost: 3-10× higher than borosilicate

Soda-Lime Glass (Economical choice)

• Room temperature, non-corrosive environments only

• Cost: 40-60% lower

3. Surface Treatment: The Invisible Detail

• Hydrophilic: Default, suitable for aqueous solutions

• Silanized Hydrophobic: Prevents biomolecule adsorption

• Heparin Coating: Anticoagulant for blood collection

• PEG Coating: Reduces nonspecific protein binding

4. Certifications & Compliance

• Medical Applications: Must comply with ISO 13485, FDA 21 CFR Part 820

• Research Grade: Batch test reports, dimensional tolerance certificates

• EU Market: CE marking, RoHS compliance required

Common Selection Mistakes & How to Avoid Them

Mistake 1: Ignoring Temperature Effects

• Problem: Ordinary glass softens/deforms at high temperatures

• Solution: Use borosilicate or quartz above 150°C

Mistake 2: Chemical Compatibility Oversight

• Case: HF acid corrodes glass; use plastic capillaries instead

• Checklist: Always consult chemical compatibility charts

Mistake 3: Size Mismatch

• Rule of Thumb: ID should be at least 10× the largest particle diameter

• Example: Cell injection requires tips 1.5× cell diameter

Conclusion

Selecting the right glass capillary tube is a systematic process requiring consideration of application scenarios, materials science, fluid dynamics, and practical operational needs. Remember: There's no "best" capillary tube, only the "most suitable" solution.

For first-time purchases, we recommend testing 2-3 similar specifications, recording usage data, and building your own selection database. For special requirements, consult directly with J&K Scientific technical support for expert customization advice.

Take Action Now: Browse our【Glass Capillary Tube Selection】to systematize your procurement decisions.

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