Laboratory Equipment: Test Tubes

Test tubes are an integral part of any laboratory whether it is for chemistry, biology, medical or other purposes.  However, laboratory equipment test tube comes in a wide variety of purposes, hence varying in shape, color, and design. 

So whether you want to set up a lab or upgrade the applications, knowing the basic information of each test tube is essential. Hence we’ve prepared this comprehensive guide covering basic information on all types of test tubes available to let you collect the right items for certain applications.

What Are Test Tubes?

In short, a test tube is simply a piece of plastic or glass tubing that has one end closed off. Though most of the test tube available in laboratories is made of glass, some lab like pathological laboratories uses clear and sterile plastic test tubes. 

The most common usage of test tubes is holding powdered material or liquid and keeping them vertically. The test tubes need to be stored in the laboratory rack that helps them remain upright and prevent accidental jolting. 

How Test Tubes Are Used

Glass test tubes are usually used to heat substances inside them. The test tubes are quite thin and considerably strong, making them an ideal container for heating liquids. Therefore most glass test tubes are designed with rounded bottoms and are mostly used in a chemistry lab. 

Depending on the usage, test tubes are also known as sample tubes or culture tubes. In bioscience or microbiology labs, plastic test tubes are used to hold any kind of small living organisms like fungi, bacteria, or plant seedlings. 

Compared to typical test tubes that remain vertically,  culture test tubes remain horizontally during breeding microorganisms to maximize the surface area. In medicine and pathology laboratories, sterile plastic tubes are used to collect and hold body fluids like urine and blood. 

Types of Test Tubes based on Size

Ignition Tubes

The ignition tubes are handy lab equipment to heat small quantities of solid powder material directly for longer times at higher temperatures. The reason is that a typical glass tube can’t cut it here as it may melt down over time. 

Hence ignition tube is designed especially for this purpose and made of thick, toughened borosilicate glass. Sodium fusion is another challenging reaction here ignition tube comes out helpful. However, the error side is that you can’t use a normal test tube brush to clean glass test tubes at the chemistry lab. 

The reason is that ignition tubes cause melted residues at the bottom side which is very difficult to scrape using a normal test tube brush. In addition, ignition tubes are quite small and brittle; hence need to be handled in a disposable manner. 

Boiling Tubes

Though a glass test tube is great for heating liquids, it causes problems during attempting to boil the liquid. During boiling liquids in such small enclosures, the test tube doesn’t get a sufficient area to allow the gas out. 

So during boiling aggressively, the liquid may blow up out of the tube and may end up causing awful accidents as well as damaging burns. 

Hence, a bigger size test tube is used in the chemistry lab, particularly for boiling things for some time. These test tubes are made of thicker walls and stronger construction.

Types of Test Tubes based on Material

Borosilicate Glass Test Tube

The borosilicate glass is manufactured of 70% to 80% silica, 7% to 13% boric oxide, and a small amount of aluminum oxide and alkaline sodium oxide. 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.

Soda-Lime Glass Test Tube

It’s one of the most common test tubes found in glass and is used for a variety of purposes. The soda lime glass is also considerably inexpensive, comparatively tough, and chemically stable. 

Quartz glass test tube

 The Quartz glass is made of a combination of high infrared (IR) radiation transmission rate and tough thermal shock resistance. This laboratory equipment test tube is also chemically robust and chemically pure and comes with decent high-temperature qualities. 

Types of Test Tubes based on Uses

Reusable Test Tubes

The Borosilicate Glass 3.3 produces a reusable test tube and it can be reused following sterilization. This sort of test tube also comes in a culture tube and glass tube variations where the culture tubes usually used to house cell cultures. It is also used for chemical reactions that need extreme accuracy. The reusable test tubes are also recyclable. 

Disposable Test Tubes

The disposable test tube is usually made of two types of glass including boro 7.0 and boro 5.1. boro is a fairly common glass tube while boro 5.1 produce two different varieties including culture tubes and glass tubes. Apart from that the disposable test tube is a cost-efficient option and can be discarded after use. 

Type of Test Tubes Based on Material 

As mentioned earlier, test tubes are made of a wide range of materials including plastic, ceramic, metal, and glass. While plastic and glass are the most common materials, ceramic and metal are less prevalent. Despite this, glass and plastic come in a variety of subtypes:

Glass Test Tubes

Glass test tubes are intended with thick walls and are resistant to chemicals and heat. Compared to plastic tubes, glass test tubes are considerably more expensive but are more transparent. 

• Fused silica is suitable for a variety of applications that require thermal stability over the long term. 
• Borosilicate glass is resistant to chemical attack and heat shock, making it a common choice for chemistry laboratories. 
• The KIMAX®is made of borosilicate glasses resistant to breaking and chemical assault and is sometimes recyclable.
• Pyrex® is also made of borosilicate glass that is heat resistant and provides more mechanical strength.
• Zerdour® is a very low extension coefficient lithium aluminosilicate glass-ceramic.

Plastic Test Tubes

The test tube produced by suppliers is made of plastic materials. These lab equipment are considerably less expensive and quite light compared to glass tubes. In addition, plastic test tubes are also resistant to pressure and UV. 

• EPDM tubes can resist elements, sunlight, and ozone. The recommended temperature range for EPDM is -70°F to 275°F.
• Fluoroelastomer materials provide impressive resistance to oil, heat, and chemicals. However, it frequently operates at lower temperatures. 
• Neoprene tubes are suitable for working in a range of temperatures and resist UV radiation. 
• Nitrile is effective laboratory equipment to work under -20°C to 135°C and perfect option for low-temperature applications.
• PharMed® test tubes come with higher tensile strength and decent pressure ratings.
• The PE test tubes come in a combination of incredible chemical resistance and poor temperature resistance. It possesses impressive chemical characteristics. 

Type of Laboratory Test Tube Based on Color

Laboratory tube collection is a process of collecting blood samples from patients before lab testing.

• Its working principle is the order of draw. A laboratory requires a wide variety types of sample tubes for different biochemical analyses and testing.
• Many manufacturers produce color-coded tubes for simple identification purposes and convenient practicality.
• In the clinical lab, blood samples need to be used in-vitro analysis. In addition, blood samples come in a wide range of ways.
• Serum may be needed for a range of diagnostic processes.
• During the collection of a variety of arterial blood samples from a single patient, the CLSI recommends using a color-coded withdrawal sequence.

Yellow, Pink, and Blue

• These shades stand for the culture bottle’s color needed for blood culture.
• Anticoagulant SPS is also stored in these tubes.

• The principal purpose of the anticoagulant is to block the activation of the balance function.
• Along with the blood collection, the content of the bottle must be mixed 8 to 10 times thoroughly.
• Blood culture vials can differ in color based on the producer.

Light Blue

The citrate tube is used to draw blood for coagulation investigations. Since it’s an anticoagulant, it’s present around 3.2% sodium citrate. Many scientists also mix blood inside this tube multiple times to create plasma. 

Red

The tube doesn’t have any additives or anticoagulants. In addition, blood comes into contact using the tube surface that activating the coagulation cascade. During the operation, blood needs to be allowed to coagulate for around 15 minutes before centrifugation to further separate the clot from the serum. However, the clotting time differs among specimens and may take up to 60 minutes. 

Green

Heparin blocks the thrombin product and performs as an anticoagulant. It can be either lithium heparin, sodium heparin, or ammonium heparin. Unlike the red tubes, the green tube requires plasma time blood instead of serum. 

Lavender

The lavender tube contains ethylene-diamine-tetra-acetic acid, hence is known as the EDTA tube. The principle of EDTA in anticoagulation is to slow down blood clotting. Since blood doesn’t clot, the liquid portion is plasma. Lavender tubes are used to collect blood samples for hematologic analyses. 

Grey

This type of tube contains potassium oxalate that inhibits coagulation by attaching to calcium. The grey tube also has sodium fluoride that works as an antiglycolytic agent. Hence this lab equipment is used to measure lactic acid and plasma glucose. 

In clinical and hospital practice, there are lots more colored tubes utilized and there are tiger, gold, and pink. The usages and reasons to order these collections vary among the medical facilities. 

However remember, you must mix Anticoagulant-containing tubes with blood and take proper care during mixing tubes. The reason is that excessive mixing can cause hemolysis. Apart from that, ineffective mixing can cause the buildup of tiny clots. Ultimately, collecting in the correct lab tube can hurt both the clinical context and the lab. 

Final Words

Test tubes are extremely versatile and helpful laboratory equipment to mix, heat, or store chemicals for laboratory and assay research. The laboratory equipment test tube is also used to manipulate and cultivate various fluids, species, and materials. As you can see, test tubes come in a wide variety of types, shapes, and colors that are designed for unique purposes. Hope this little knowledge will help you collect the right test tube for your lab for certain research and analysis.