Laboratory Test Tube – Types, Materials, Function, Uses in Science

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A scientist wearing a lab coat holding up a test tube after some major breakthrough is a classic scene in movies and television. Perhaps the movie scientist created a cure for a deadly disease or a solution that grants superpowers. Or perhaps an evil scientist created a formula that will transform every human being on the planet into a giant beetle. Although the test tube has had many exciting supernatural and pseudoscientific roles in movies, its use in the laboratory by scientists in real life is much more practical. So, what is a test tube? Test tubes are not aesthetic props for miraculous discoveries in laboratories, but they are nonetheless important tools used by microbiologists, biologists, chemists, biochemists, food scientists, laboratory technicians, medical researchers, and more. A test tube is defined as a small, long plastic cylinder with one open end used to store, mix, or hold liquids, bodily fluids, bacteria, or chemicals.

What is the Test Tube?

• A test tube, culture tube, or sample tube is a clear, cylindrical container that is typically open at one end and closed at the other.

• Michael Faraday, a prominent British Physicist and Chemist, invented the test tubes (1791-1867).

• Boiling tubes are another name for test tubes.

• These slim containers have a U-shaped base and an open top.

• They can contain small quantities of liquids and are typically employed in scientific research.

• Typically, test tubes are stored in specialised racks.

• Beginning in the 19th century, it has been used to contain and evaluate diverse reactions on a small scale.

• They have numerous applications in chemistry, biology, and medicine, among others.

• Due to the absence of corners, the spherical bottom reduces mass loss when pouring the contents of the test tube and facilitates cleaning.

• There are numerous test tube materials, including glass, plastic, metal, and ceramic. The most popular materials are glass and plastic; some are designed for reuse, while others are disposable.

Types of test tubes

Types of Test Tube based on Material

1. Soda-lime glass test tube

• Standard soda-lime glass is the most common type of glass.

• It is composed of around 70% silica (silicon dioxide), 15% soda (sodium oxide), and 9% lime (calcium oxide), along with much lower amounts of other chemicals.

• Soda lime glass is inexpensive, chemically stable, and comparatively tough.

2. Borosilicate glass test tube

• 70% to 80% silica (SiO 2), 7% to 13% boric oxide (B2O3), and minor amounts of alkaline sodium oxide (soda) (Na 2O) and d aluminium oxide are used to manufacture borosilicate glass (AI2O3).

• Borosilicate glass is superior to soda lime glass in various ways. It is less susceptible to chemical assault and has a lower expansion coefficient, making it more resistant to thermal stress.

3. Quartz glass test tube

• Quartz glass combines a strong thermal shock resistance with a high infrared (IR) radiation transmission rate.

• In addition to being chemically pure and chemically robust, it possesses good high temperature qualities.

4. Pyrex® glass test tube

• Pyrex Glass is an additional patented borosilicate glass with remarkable strength and stability, dazzling transparency, and superior resistance to chemicals, impurities, and extreme temperature fluctuations.

Types of Test Tubes based on Uses

1. Reusable Test Tubes

• These sorts of test tubes are produced from Borosilicate Glass 3.3 of the finest quality.

• Following sterilisation, these tubes can be reused.

• Additional varieties include Glass Tubes and Culture Tubes. Glass Tubes – These are typically used in laboratories for heating, boiling, and conducting experiments. Culture Tubes – In laboratories, these tubes are typically used to house Cell Cultures.

• Reusable Test Boro 3.3 Glass is used to produce tubes that are more durable and resistant to high temperatures.

• These are employed for chemical reactions requiring extreme precision. They are recyclable.

2. Disposable Test Tubes

• These test tubes are made from two different types of glass: Boro 5.1 and Boro 7.0.

• Boro 5.1: The Boro 5.1 test tube is produced in two distinct varieties: glass tubes and culture tubes.

• Boro 7.0: In contrast, Boro 7.0 tubes are common Glass Tubes.

• The disposable test tubes are very cost-effective and are discarded after use.

Types of Test Tubes based on Size

1. Boiling tube

• A boiling tube is a small cylindrical receptacle used to rapidly heat items in the flame of a Bunsen burner.

• Essentially, a boiling tube is a test tube that is approximately 50 percent larger.

• They are meant to be wide enough to allow substances to boil furiously, as opposed to a test tube, which is too narrow; a boiling liquid can explode out of the end of a test tube when it is heated because there is no area for gas bubbles to escape separately from the surrounding liquid. The term for this occurrence is bumping.

2. Ignition tube

• An ignition tube is utilised similarly to a boiling tube, except that it is smaller and has thinner walls.

• Its primary purpose is to retain small amounts of substances that are being heated directly by a Bunsen burner or other heat source.

• In the sodium fusion test, this type of tube is utilised.

• Due to their narrow bore, ignition tubes can be difficult to clean. When used to heat material vigorously, char may adhere to the walls.

• Typically, they are disposable.

Material Used for Test Tube

Test tubes come in a variety of materials, including glass, plastic, metal, and ceramic. Glass and plastic are the most prevalent materials, whereas metal and ceramic are less prevalent. There are various subtypes of plastic and glass test tubes.

Glass Test Tubes

Glass test tubes have thick walls and are resistant to heat and/or chemicals. They are frequently more expensive than plastic tubes, but occasionally more transparent.

• Fused silica is suited for applications requiring excellent thermal stability over the long term.

• Borosilicate glass can resist heat shock and chemical attack, making it a common material for test tubes used in chemistry.

• Quartz glass combines strong thermal shock resistance with high infrared radiation transmission (IR). In addition to being chemically pure and chemically robust, it possesses exceptional high-temperature qualities.

• KIMAX® (Kimble Chase) is composed of borosolicate glasses and is resistant to chemical assault and breaking. Occasionally, it is disposable and/or recyclable.

• Pyrex® (Corning) is a proprietary boroslicate glass product. Similar to KIMAX, it possesses more mechanical strength and heat resistance than comparable commercial glasses.

• Zerdour® (Schott Glass) is an extremely low expansion coefficient lithium aluminosilicate glass-ceramic.

• Other varieties of laboratory glassware are also available.

Plastic Test Tubes

• Additionally, suppliers offer test tubes built from a range of plastic materials. These items are typically less expensive and lighter than glass tubes. Additionally, they may resist ultraviolet (UV) radiation and pressure.

• EPDM tubes are resistant to sunlight, the elements, and ozone. -70°F to 275°F is the suggested operating temperature range for EPDM.

• Fluoroelastomer materials have excellent resistance to heat, oil, and chemicals, although they frequently operate poorly at low temperatures.

• Neoprene tubes are effective over a broad temperature range and are resistant to UV radiation damage.

• Nitrile has a recommended operating temperature range of -20°C to 135°C, making it a suitable material for low-temperature applications.

• Test tubes manufactured by PharMed® (Norton Company) have a high tensile strength. Nylon and polyamide products have good pressure ratings.

• Excellent chemical resistance, but poor temperature resistance, characterise PE test tubes. Polyethylene (PE) likewise possesses exceptional chemical characteristics, however it is only partially opaque.

• There are also polypropylene (PP), polytetrafluoroethylene (PTFE), polyurethane (PU), and polyvinyl chloride (PVC) test tubes (PVC).

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.

Type or color of tube cap, in the order of draw	Additive	Comment and use
Blood culture bottle	Sulfonate of sodium polyanethol ( anticoagulant) and growth medium that are suitable for the growth of microorganisms	Most often, blood draws are drawn first to reduce the chance of contamination. Two bottles are typically drawn within a single blood draw: the one is for organisms that are aerobic, and the other for anaerobic organisms. The latter is the most common.
Light blue	Sodium citrate (anticoagulant)	Tests for coagulation including the prothrombin test (PT) along with partial thromboplastin times (PTT) as well as the thrombin time (TT). Tubes must be filled to completely.
Plain red	No added	Serum: Total complement activity, cryoglobulins
Gold (sometimes grey and red “tiger Top”)	Clot activator and serum separating gel	Serum-separating tubes Tube inversions can promote the formation of clots. A majority of chemistry, endocrine, as well as serological tests such as the hepatitis virus as well as HIV.
Dark green	Sodium Heparin (anticoagulant)	Chromosome testing, HLA typing, ammonia, lactate
Light green	Lithium Heparin (anticoagulant)	Plasma. Tube inversions stop clotting.
Lavender (“purple”)	EDTA ( chelator / anticoagulant)	Complete blood analysis: CBC, ESR, Coombs test Platelet antibody, flow cytometry levels of tacrolimus in blood and the cyclosporin
Pink	EDTA (chelator or anticoagulant)	Cross-matching and blood typing, the direct Coombs Test, HIV viral load
Royal blue	EDTA (chelator or anticoagulant)	Trace elements, heavy metals, most drug levels, toxicology
Tan	EDTA (chelator or anticoagulant)	Lead
Gray	Sodium fluoride (glycolysis inhibitor)Potassium oxalate (anticoagulant)	Glucose, lactate
Yellow	Acid-citrate-dextrose A (anticoagulant)	Tissue typing, DNA studies, HIV cultures
“White” Pearl (“white”)	Separating gel and (K2)EDTA	The PCR test for adenovirus and toxoplasma and the HHV-6

Advantages of test tube

• Simple and secure usage

• Temperature Resistant

• Chemically Resistant

• Dimensional Uniformity

• Ideal for medical and industrial applications

• Environment friendly

Disadvantages

Inherent to the application of laboratory tube collection are the following, but not limited to:

• Problems with the evacuated tube system (ETS): Multiple blood collections will be challenging, especially if the employed vacutainer is broken or malfunctioning.

• There may also be issues with the collection tubes, which may be broken. For instance, the vacuum inside the tube may be lost if the cap is removed. Alternatively, an anticoagulant may not be included in some tubes during packaging, resulting in the improper use of serum for testing.

• Inadequately trained workers: The laboratory staff should be trained in tube collection. Color-coding simplifies the sequence of draw, but if the phlebotomist does not follow the order of draw due to insufficient training, it might still lead to an inaccurate blood sample collection.

• Contamination: If the tubes are contaminated before, during, or after the collection, the results will be inaccurate and unreliable. For instance, the cap of blood culture tubes must be sterile and should not come into contact with any potential contamination source. When the anticoagulant from one tube adheres to the needle of the vacutainer, it can move to another tube and cause contamination.

• Lack of research studies on laboratory tube collection: While the CLSI offered guidelines for the proper order of tube collection, additional studies are required to disclose the true degree of variability when tubes are collected in the incorrect order. Future research can elucidate the underlying principles of the laboratory tube collecting procedure, which can aid in the development of future laboratory science standards for healthcare. Medical laboratory scientists employed not only in clinical laboratories, but also in research and academia, should devote enough attention to laboratory tube collection, as it is now given less priority despite its clinical importance.

Uses of Test Tubes

• Test tubes are used by chemists to combine, heat, and/or store small amounts of chemicals for assays and laboratory research.

• They are utilised by biologists to cultivate and manipulate various species, fluids, and materials.

• Some test tubes, such as those used for coagulation screening, include prepared substances.

• Blood collection tubes in hospitals, labs, and other medical facilities feature coloured lids or stoppers (screw caps) for identifying certain types and screens.

Test Tube Function

Test tubes are used primarily for qualitative observations of biological, biochemical, or chemical reactions. They are not used for measuring liquids or solutions like graduated cylinders. Biologists, biochemists, chemists, microbiologists, and biomedical scientists use test tubes in different ways. So, what is a test tube used for? Test tube functions in the real world are diverse, but their most common uses in the laboratory are as containers to:

• Grow or identify microorganisms

• Hold bodily fluids or liquid solutions

• Heat solutions

• Use as mixing vessels for observing reactions

Test Tubes in the Biological Sciences

Biologists, biochemists, and microbiologists primarily use test tubes to mix samples, make qualitative observations of reactions, and perform genetic sequencing tests of humans, plants, fungi, parasites, animals, viruses, or bacteria. Microbiologists also use test tubes to culture, identify, and store microorganisms like bacteria or fungi. When microbiologists grow bacteria in glass test tubes, the tubes are capped loosely to allow some oxygen to get into the container. A few examples of how biologists or microbiologists use test tubes include:

• Centrifuge and microcentrifuge tubes: These are capped plastic tubes with graduated markings and a conical bottom. They are used to mix or physically separate the contents of samples in a high-speed spinning device.

• PCR tubes: Microcentrifuge tubes with snap caps that hold 0.2 mL or 0.5 mL of liquid are called PCR tubes, which are used for genetic sequencing tests.

• Glass test tubes: Glass tubes are frequently used as containers for qualitative observations of chemical or biochemical reactions. When indicators are added to solutions or broth, they cause observable changes (like a color change) based on the presence or absence of certain chemicals.

• Agar culture tubes: These are usually screw-capped glass tubes filled with plant-based gelatin called agar. They are used to grow, culture, and identify bacteria in a microbiology lab.

• Broth culture tubes: These are usually screw-capped glass tubes filled with nutrient broth. They are also used to grow, culture, and identify bacteria.

References

Bayot ML, Tadi P. Laboratory Tube Collection. [Updated 2021 Aug 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK555991/

https://www.homesciencetools.com/product/glass-test-tubes/

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