 Two small test tubes held in spring clamps | |
| Other names | Culture tube |
|---|---|
| Uses | Chemical reaction |
| Related items | Vacutainer Boiling tube Centrifuge tube |
Atest tube, also known as aculture tube orsample tube, is a common piece oflaboratory glassware consisting of a finger-like length ofglass or clearplastic tubing, open at the top and closed at the bottom.
Test tubes are usually placed in special-purposeracks.
Test tubes intended for general chemical work are usually made of glass, for its relative resistance to heat. Tubes made from expansion-resistant glasses, mostlyborosilicate glass orfused quartz, can withstand high temperatures up to several hundred degreesCelsius.
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 aground glass stopper or ascrew cap. They are often provided with a smallground glass or whiteglaze area near the top for labelling with a pencil.
Test tubes are widely used bychemists 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 aBunsen burner oralcohol burner. The tube is usually held by its neck with aclamp ortongs. By tilting the tube, the bottom can be heated to hundreds of degrees in the flame, while the neck remains relatively cool, possibly allowing vapours to condense on its walls. Aboiling tube is a large test tube intended specifically for boiling liquids.
A test tube filled with water and upturned into a water-filledbeaker is often used to capturegases, e.g. inelectrolysis demonstrations.
A test tube with astopper is often used for temporary storage of chemical or biological samples.
Culture tubes are test tubes used inbiology and related sciences for handling and culturing all kinds of liveorganisms, such asmolds,bacteria,seedlings,plant cuttings, etc.. Some racks for culture tubes are designed to hold the tubes in a nearly horizontal position, so as to maximize the surface of theculture medium inside.
Culture tubes for biology are usually made of clear plastic (such aspolystyrene orpolypropylene) byinjection molding[2] and are often discarded after use. Plastic test tubes with a screwtop cap are often called "Falcon tubes" after a line manufactured byBecton Dickinson.[3]
Some sources consider that the presence of a lip is what distinguishes a test tube from a culture tube.[4]
In clinical medicine, sterile test tubes with air removed, calledvacutainers, are used to collect and holdsamples of physiological fluids such asblood,urine,pus, andsynovial fluid. These tubes are commonly sealed with a rubber stopper and often have a specific additive placed in the tube with the stopper color indicating the additive. For example, ablue-top tube is a 5 ml test tube containingsodium citrate as an anticoagulant, used to collect blood forcoagulation andglucose-6-phosphate dehydrogenase testing.[5] Smallvials used in medicine may have a snap-top (also called a hinge cap) molded as part of the vial.
| Tube cap color or type in order of draw | Additive | Usage and comments |
|---|---|---|
| Blood culture bottle | Sodium polyanethol sulfonate (anticoagulant) andgrowth media formicroorganisms | Usually drawn first for minimal risk of contamination.[6] Two bottles are typically collected in one blood draw; one foraerobic organisms and one foranaerobic organisms.[7] |
| Blue ("light blue") | Sodiumcitrate (weak calcium chelator/anticoagulant) | Coagulation tests such asprothrombin time (PT) andpartial thromboplastin time (PTT) andthrombin time (TT). Tube must be filled to the proper line. |
| Plain red | No additive | Serum:Total complement activity,cryoglobulins |
| Gold (sometimes red and grey "tiger top"[8]) | Clot activator andserum separating gel[9] | Serum-separating tube (SST): Tube inversions promote clotting. Most chemistry, endocrine and serology tests, includinghepatitis andHIV. |
| Orange | Clot activator andserum separating gel[10] | Rapidserum-separating tube (RST). |
| Dark green | Sodiumheparin (anticoagulant) | Chromosome testing,HLA typing,ammonia,lactate |
| Light green | Lithiumheparin (anticoagulant) Plasma separator gel | Plasma. Tube inversions prevent clotting |
| Lavender ("purple") | EDTA (chelator /anticoagulant) | Whole blood:CBC,ESR,Coombs test, platelet antibodies,flow cytometry, blood levels oftacrolimus andcyclosporin |
| Pink | K2 EDTA (chelator /anticoagulant) | Blood typing andcross-matching, directCoombs 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 | PCR foradenovirus,toxoplasma andHHV-6 |
| Black | Sodium Citrate | PaediatricESR |
| 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 |
Test tubes are sometimes put to casual uses outside of lab environments, e.g. asflower vases, glassware for certain weakshots, or containers forspices. They can also be used for raising queen ants during their first months of development.
A boiling tube is a small cylindrical vessel used to strongly heat substances in the flame of aBunsen 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 calledbumping.
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 thesodium fusion test.
Ignition tubes are often difficult to clean due to the small bore. When used to heat substances strongly, somechar may stick to the walls as well. They are usually disposable.
