Test tube

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Test tube
Centrifuge tube

A test tube, also known as a culture tube or sample tube, is a common piece of laboratory glassware consisting of a finger-like length of glass or clear plastic tubing, open at the top and closed at the bottom.

Test tubes are usually placed in special-purpose racks.

Types and usage

Louis Lumière with a microscope and some test tubes

Chemistry

Test tubes intended for general chemical work are usually made of glass, for its relative resistance to heat. Tubes made from expansion-resistant glasses, mostly borosilicate glass or fused quartz, can withstand high temperatures up to several hundred degrees Celsius.

Chemistry tubes are available in a multitude of lengths and widths, typically from 10 to 20 mm wide and 50 to 200 mm long.[1] The top often features a flared lip to aid pouring out the contents.

A chemistry test tube typically has a flat bottom, a round bottom, or a conical bottom. Some test tubes are made to accept a

glaze
area near the top for labelling with a pencil.

Test tubes are widely used by chemists to handle chemicals, especially for qualitative experiments and assays. Their spherical bottom and vertical sides reduce mass loss when pouring, make them easier to wash out, and allow convenient monitoring of the contents. The long, narrow neck of test tube slows down the spreading of gases to the environment.

Test tubes are convenient containers for heating small amounts of liquids or solids with a

boiling tube
is a large test tube intended specifically for boiling liquids.

A test tube filled with water and upturned into a water-filled

beaker is often used to capture gases, e.g. in electrolysis
demonstrations.

A test tube with a stopper is often used for temporary storage of chemical or biological samples.

Samples of human blood collected for blood tests

Biosciences

Culture tubes are test tubes used in

culture medium
inside.

Culture tubes for biology are usually made of clear plastic (such as

Becton Dickinson.[3]

Some sources consider that the presence of a lip is what distinguishes a test tube from a culture tube.[4]

Clinical medicine

In clinical medicine, sterile test tubes with air removed, called

ml test tube containing sodium citrate as an anticoagulant, used to collect blood for coagulation and glucose-6-phosphate dehydrogenase testing.[5] Small vials
used in medicine may have a snap-top (also called a hinge cap) molded as part of the vial.

Vacutainer/sample tube types for venipuncture/phlebotomy   edit
Tube cap color or type in order of draw Additive Usage and comments
Blood culture bottle Sodium polyanethol sulfonate (
microorganisms
Usually drawn first for minimal risk of contamination.[6] Two bottles are typically collected in one blood draw; one for aerobic organisms and one for anaerobic organisms.[7]
Blue

("light blue")

Sodium citrate

(weak calcium chelator/anticoagulant)

Coagulation tests such as prothrombin time (PT) and partial thromboplastin time (PTT) and thrombin time (TT). Tube must be filled 100%.
Plain red No additive Serum:
cryoglobulins
Gold (sometimes red and grey "tiger top"[8]) Clot activator and serum separating gel[9] Serum-separating tube (SST): Tube inversions promote clotting. Most chemistry, endocrine and serology tests, including hepatitis and HIV.
Orange Clot activator and serum separating gel[10] Rapid serum-separating tube (RST).
Dark green Sodium heparin (anticoagulant) Chromosome testing, HLA typing, ammonia, lactate
Light green Lithium heparin (anticoagulant)

Plasma separator gel

Plasma. Tube inversions prevent clotting
Lavender ("purple") EDTA (chelator / anticoagulant)
cyclosporin
Pink K2 EDTA (
chelator / anticoagulant
)
Blood typing and cross-matching, direct Coombs test, HIV
viral load
Royal blue

("navy")

EDTA (
chelator / anticoagulant
)
Trace elements, heavy metals, most drug levels, toxicology
Tan Sodium EDTA (
chelator / anticoagulant
)
Lead
Gray

Fluoride Oxalate

Glucose, lactate,[12] toxicology[13]
Yellow Acid-citrate-dextrose A (anticoagulant) Tissue typing, DNA studies, HIV cultures
Pearlescent ("white") Separating gel and (K2)EDTA
toxoplasma and HHV-6
Black Sodium Citrate
Paediatric ESR
QuantiFERON

Grey, Green, Yellow, Purple

QuantiFERON

1. Grey (nil) tube 2. Green (TB1 antigen) tube 3. Yellow (TB2 antigen) tube 4. Purple (mitogen) tube

Tuberculosis

Other uses

Test tubes are sometimes put to casual uses outside of lab environments, e.g. as

shots, or containers for spices
. They can also be used for raising queen ants during their first months of development.

Variants

Boiling tube

A boiling tube is a small cylindrical vessel used to strongly heat substances in the flame of a Bunsen burner. A boiling tube is essentially a scaled-up test tube, being about 50% larger.

They are designed to be wide enough to allow substances to boil violently as opposed to a test tube, which is too narrow; a boiling liquid can explode out of the end of test tubes when they are heated, as there is no room for bubbles of gas to escape independently of the surrounding liquid. This phenomenon is called bumping.

Ignition tube

An illustration of a setup using an ignition tube. The ignition tube is being heated by the Bunsen burner on the left, with the heated gas escaping from the tube to the pan via the delivery tube on top and at right.

An ignition tube is used in much the same way as a boiling tube, except it is not as large and thick-walled. It is primarily used to hold small quantities of substances which are undergoing direct heating by a Bunsen burner or other heat source.[14] This type of tube is used in the sodium fusion test.

Ignition tubes are often difficult to clean due to the small bore. When used to heat substances strongly, some char may stick to the walls as well. They are usually disposable.

See also

Eight-cavity culture-tube mold (Lake Charles Manufacturing)

References

  1. ^ MiniScience.com catalog: Test Tube, accessed March 27, 2009.
  2. ^ M. Jeremy Ashcraft; General Manager; Lake Charles Manufacturing (2007). Test Tube Molding Process: A discussion on the molding of plastic test tubes. Lake Charles Manufacturing.
  3. Becton Dickinson
    . Retrieved 14 March 2016.
  4. . 1287 pages.
  5. ^ TheFreeDictionary > blue top tube. Citing: McGraw-Hill Concise Dictionary of Modern Medicine. 2002 by The McGraw-Hill Companies, Inc.
  6. .
  7. .
  8. ^ "Test Tube Guide and Order of Draw" (PDF). Guthrie Laboratory Services. June 2019.
  9. ^ "Specimen requirements/containers". Pathology & Laboratory Medicine, UCI School of Medicine. Retrieved 2020-09-10.
  10. ^ "Proper Order of Draw" (PDF). Memorial Lab Services. Retrieved 2023-06-15.
  11. PMID 1644639
    .
  12. .
  13. ^ "What types of samples will the Toxicology Lab analyze?". Oklahoma State Bureau of Investigation. Retrieved 2024-01-24.
  14. ^ Nichols, William Ripley (1877). An Elementary Manual of Chemistry: Abridged from Eliot and Storer's Manual, with the Co-operation of the Authors. Ivison, Blakeman, Taylor.