Laboratory Test Tube – Types, Limitations, Advantages, Uses

What is the Test Tube?

• A test tube is a compact, cylindrical piece of scientific equipment, usually constructed of glass or plastic.
• It is perfect for storing, mixing, and heating little quantities of chemicals as its top is open and its bottom is closed or rounded.
• In biology and chemistry, it is often utilized in qualitative tests and reactions.
• A test tube’s design lets one readily observe chemical or biological responses and reduces material loss while pouring.
• In scientific study, variants like NMR tubes, boiling tubes, and culture tubes fulfill specific purposes.
• Test tubes are crucial in clinical and scientific environments for sample storage, microorganistory, and small-scale experimentation.

Types of test tubes

1. Standard Test Tubes: Often used for mixing and heating tiny amounts of chemicals, cylindrical tubes with rounded bottoms are standard test tubes.
2. Culture Tubes: Designed for cultivating microorganisms and cell cultures, Culture Tubes are like ordinary test tubes only without a lip.
3. Centrifuge Tubes: Designed to resist high-speed centrifugation, sometimes conical at the bottom to enable the sediment collecting process, centrifuge tubes:
4. Boiling Tubes: Designed for boiling liquids, larger, heat-resistant glass boiling tubes.
5. Ignition Tubes: Thick-walled tubes used for highly heating compounds to high temperatures are called ignition tubes.
6. NMR Tubes: Sample-holding thin-walled tubes used in nuclear magnetic resonance spectroscopy.
7. Thiele Tubes: Designed especially to find the melting point of materials, thiele tubes
8. Reusable Test Tubes: Made from robust materials like borosilicate glass, reusable test tubes fit for sterilizing and frequent use.
9. Disposable Test Tubes: Usually composed of plastic, disposable test tubes are meant for one usage in order to avoid cross- contamination.
10. Graduated Test Tubes: Marked with capacity graduations to precisely gauge liquids, graduated test tubes
11. Screw-Capped Test Tubes: Useful for storage and transportation, screw-capped test tubes include threads to tightly seal the contents.
12. Rimmed Test Tubes: Features a flared lip at the top for more strength and simpler handling with clamps or holders.
13. Plain Top Test Tubes: Commonly employed in conventional laboratories, plain top test tubes have a straight, non-flared top.
14. Thin-Walled Test Tubes: The thinner glass walls of thin-walled test tubes fit uses needing quick heat transmission.
15. Thick-Walled Test Tubes: Ideal for high-pressure or high-temperature uses, thicker glass walls seen in thick-walled test tubes

Material Used for Test Tube

1. Borosilicate Glass: Perfect for uses involving rapid temperature fluctuations, borosilicate glass is quite resistant to chemical damage and thermal stress.
2. Soda-Lime Glass: Comprising silica, soda, and lime, soda-lime glass is cheap, chemically stable, and somewhat strong.
3. Plastic: Appropriate for tests not involving high temperatures or reactive chemicals; lightweight and less prone to breaking.
4. Quartz: Perfect for uses needing robust, long-term thermal stability, quartz combines great resistance to thermal stress with strong infrared radiation transmission.

Laboratory Tube Collection Based on Color

• Laboratory tube collection is the procedure used to collect blood samples from patients prior to laboratory testing.
• It adheres to the principle, which is often known as “order of draw.” Different types of sample collection tubes are required for various testing and biochemical analyses.
• Tubes are color-coded for practical and simple identifying purposes.
• In clinical laboratories, blood samples can undergo in-vitro analysis. However, blood samples come in a variety of ways.
• Serum or plasma blood samples may be required for a variety of diagnostic procedures.
• When collecting several venous and/or arterial blood samples from a single patient, the Clinical & Laboratory Standards Institute (CLSI) suggests using a color-coded withdrawal sequence and corresponding indications.

Yellow, Pink, and Blue

• These hues represent the colour of the culture bottles required for blood culture.
• Anticoagulant sodium polyanethole sulphate (SPS) is contained in these tubes (bottles).
• This anticoagulant’s principal purpose is to block the activation of complement function.
• Following the collection of blood, the bottle’s contents must be thoroughly mixed eight to ten times.
• Blood culture vials can vary in colour depending on the manufacturer.

Light Blue

• The “citrate tube” is utilised to draw blood for coagulation investigations.
• As an anticoagulant, 3.2% sodium citrate is present.
• To create plasma, it is also recommended to mix the blood within the tube several times.

Red

• The tube contains no anticoagulant or additive. Blood coming into contact with the surface of the tube activates the coagulation cascade.
• Blood is allowed to coagulate for 10 to 15 minutes prior to centrifugation in order to further separate the clot from the serum.
• Clotting time varies among specimens and might range from ten minutes to nearly an hour (60 minutes).

Green

• Heparin (either sodium heparin, lithium heparin, or ammonium heparin) serves as an anticoagulant by blocking thrombin production.
• In contrast to red tubes, the type of blood required for testing in green tubes is plasma, not serum.
• When requesting “stat” or immediate blood chemistry readings, green tubes are usually utilised.

Lavender

• Because it contains ethylene-diamine-tetra-acetic acid, the lavender tube is also known as EDTA tubes.
• The fundamental function of EDTA in anticoagulation is to inhibit blood clotting by chelating calcium ions.
• Because the blood does not clot, the liquid portion (sans red cells) is plasma.
• Blood samples for hematologic analyses are often collected using lavender tubes.

Grey

• The grey tubes contain potassium oxalate, which inhibits coagulation by binding to calcium.
• The tubes also contain sodium fluoride, a chemical that functions as an antiglycolytic agent.
• Therefore, it is utilised for measuring plasma glucose and lactic acid.

In actual hospital and clinical practise, additional coloured collection tubes (gold, tiger, pink, gold, etc.) are also employed. The use of these tubes and the order of collection differ amongst medical facilities. Anticoagulant-containing tubes must be adequately mixed with blood. However, care must be taken when mixing tubes, as excessive mixing can result in hemolysis. Ineffective mixing might lead to the formation of tiny clots. Incorrect laboratory tube collection can cause harm in both the laboratory and the clinical context.

Limitations of test tube

• Restricted volume capacity limits test tubes to sample handling and small-scale reactions.
• In tests, poor heat transfer qualities can cause unequal heating and temperature control.
• Especially with glass test tubes, fragile construction raises the possibility of breakage and possible sample loss.
• Many test tube designs have inaccurate measurements made harder by insufficient exact volume marks.
• Non-airtight construction could let samples be contaminated or evaporated over time.
• Limited stability resulting from narrow bases might cause test tubes to tip over readily under handling.
• Certain materials, like certain plastics, are not appropriate for high-temperature uses, which limits their usage in particular tests.

Advantages of test tube

• Transparent for easy observation.
• Durable and chemically resistant.
• Versatile for mixing, heating, and reactions.
• Requires small volumes, reducing waste.
• Easy to clean and sterilize for reuse.

Uses of Test Tubes

• Mixing small amounts of chemicals.
• Heating liquids during experiments.
• Observing chemical reactions.
• Culturing microorganisms in biology labs.
• Collecting and storing samples.
• Conducting qualitative tests.