Guide to selecting the best tubing and connectors for In Vitro Diagnostics instrumentation

In vitro diagnostic (IVD) instrumentation is used in a variety of healthcare applications to detect many different human elements related to patient diagnosis and treatment. IVD instruments are used for sample preparation, blood chemistry, therapeutic drug monitoring, electrochemistry, urinalysis and disease detection. Every analysis begins with a patient sample and ends with lab results used in treatment or diagnosis of a patient. Each IVD instrument requires that fluids be mixed in the form of samples, diluents, assays, reagents and test markers. As a result, these systems use a complex set of subsystems including pumps, mixing devices, reaction tubes and optical readers to produce a wide list of details about the patient. Bringing all these subsystems together requires a variety of different connectors and tubing to carry the fluidics from sample to test tube to reaction tube. Utilizing the right tubing and connectors for each application is the challenge of the instrumentation designers and manufacturers.

Tubing connectors used in IVD instrumentation typically include:

• Barb-to-barb connectors in straights, Ts, Ys and elbows for connections to tubing. These connectors are often used in pump applications, especially peristaltic pumps and syringe drive pumps.
• Luer-to-barb connections are used when a tubing connection needs to be made, but it is not permanent. With luer connectors, it is easy to connect and disconnect tubing without cutting.
• Valves are needed primarily to protect pumps and other systems. These connectors stop backflow when there is an obstruction in the line.
• Panel mounts are often used to connect tubing to a pump or valving system. These connectors usually have a luer connection end, which allows for quick connect and disconnect. On the inside of the panel, the connector may have a barb or compression connection to connect to a pump system on a more permanent basis.
• Stopcocks may be used to manually control flow in one direction or in multiple directions. This may be needed to change flow from a reagent or diluent bottle.
• Quick disconnect components are often needed instead of luers when it is necessary to connect or disconnect two tubing lines without flow leaking through the tubing. When valved components are disconnected, the flow in the tubing line is blocked.
• Sample tubes and centrifuge tubes are both needed for sample preparation and testing of samples within the IVD instrument.
• Compression fittings are often used for connections with tubing instead of barb fittings. These fittings are necessary when the inside diameter of the tubing is very small. In these cases, barb fittings are too large or too difficult to assemble with tubing. It is much easier to use a compression fitting to grip the outer diameter of the tubing.
• Tubing of varying length and size is necessary to carry fluid for sample preparation, mixing and testing. In a typical IVD instrument, there are usually multiple feet of tubing in varying sizes, durometer and material.

Selecting the proper material for tubing connections as described above is also a very important factor. Many systems use polypropylene connectors because these connectors provide sufficient chemical resistance and come in readily available sizes to meet most tubing sizes. If the chemicals used in the application are not compatible with a material like polypropylene, a stronger chemical resistive connector material may be used such as PVDF or PEEK. Both plastics are highly resistant to chemicals. Before selecting a material, it is strongly recommended to make sure the plastic will withstand the chemicals it comes into contact with. Most companies that sell plastic components can provide technical details including a chemical resistant chart for all plastic resins used in their production of parts from plastic resin.

Most plastics will work reasonably well with the primary chemicals used in IVD testing systems. If polycarbonate or ABS components are the only materials available, check the chemical resistance table for which chemicals will be in contact. If in doubt, call Qosina’s technical support line for further information on plastics compatible with your application.

Reliable connections for your medical device start with finding the proper combination of tubing, fittings and connectors. Qosina is a one-stop source offering all the components and tubing described in this article. In addition, Qosina has set up an IVD application on its website, specifically for IVD component selection. Explore Qosina’s full line of IVD components at www.qosina.com/ivd-in-vitro-diagnostics.

Qosina’s application specialists are available to discuss your specific requirements and provide complimentary samples for your review. Contact us at +1 (631) 242-3000 or email marketing@qosina.com.