Is the capillary tube for collecting tear fluid a disposable micro blood collection tube?

Typically, the capillary tubes used for tear fluid collection are not the ordinary disposable micro blood collection tubes, but specialized glass or plastic capillary tubes without additives or coatings. Common specifications include an inner diameter of 0.5–1.0 mm, a length of about 5–10 cm, and a capacity of 1–10 µL.

 

Main Differences

1. No anticoagulants or other additives: Blood collection capillary tubes usually have heparin or other anticoagulants coated on the inner wall, which may interfere with subsequent proteomics or metabolomics analysis.

2. No adsorption coating or inert treatment: The sample volume of tear fluid is extremely small, and the concentration of proteins and metabolites is low; any coating may cause loss of analytes or introduce background noise.

3. Precise volume control: Tear fluid collection often requires quantification (e.g., for tear flow tests or quantitative omics), necessitating the use of capillary tubes with known inner diameters and precise graduations.

 

Recommendations

1. Use borosilicate capillary tubes specifically designed for collecting tear fluid or micro biological liquids, avoiding blood collection tubes.

2. Seal both ends immediately after collection to prevent evaporation and store at low temperatures to minimize sample loss.

 

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