Views: 0 Author: Kevin Fang Publish Time: 2026-11-17 Origin: Chensheng Medical
A pharmaceutical fluid can enter a tubing assembly at the correct concentration and leave it at a lower one—even when there is no visible leak.
One possible cause is sorption: the interaction between a product component and the surfaces it contacts. In a silicone tubing fluid path, some compounds may adhere to the tubing surface or move into the material. Whether that occurs at a meaningful level depends on the specific drug, formulation, tubing, and process conditions.
For buyers, this creates a different qualification question from the more familiar issue of extractables and leachables. Instead of asking what might move from the tubing into the product, a sorption assessment asks whether an important component might move from the product into or onto the tubing.
Not every pharmaceutical process needs an extensive sorption study. But when concentration, dose recovery, or formulation consistency is critical, the question should be addressed before a tubing material is approved for production.
Sorption is a broad term that includes two related phenomena:
Adsorption: A substance associates with the surface of the tubing.
Absorption: A substance moves into the tubing material.
In practice, both can contribute to a measured reduction in the concentration of a product component after it contacts a fluid path. A concentration change alone does not show which mechanism occurred, and it does not prove that the tubing was the cause.
The distinction matters because different components in an assembly can also affect recovery. Connectors, bags, filters, pumps, and sampling containers may all contact the fluid. An appropriate study must account for the complete system while providing a way to investigate the tubing’s contribution.
The risk is application-specific. A long tubing run used to transfer a high-volume buffer may present a very different concern from a short line carrying a small quantity of a potent drug solution.
A closer assessment may be warranted when:
the active ingredient has a narrow acceptable concentration range;
the process handles small product volumes;
fluid remains in the tubing for an extended period;
the formulation contains a component known or suspected to interact with contact materials;
low-concentration samples must remain representative; or
unexpected product loss has been observed during transfer or filling.
The presence of silicone tubing does not, by itself, establish that sorption will be significant. Likewise, a supplier’s general statement that tubing is suitable for pharmaceutical use does not establish acceptable recovery for a particular formulation.
The useful question is: Does the proposed fluid path maintain the required product concentration under the intended conditions of use?
The effect of a given amount of product loss depends on how much product is present. A loss that is insignificant in one process may be important in another, particularly where the initial concentration or processed volume is low.
Contact time also matters. A fluid that passes quickly through tubing may behave differently from one held in a filled line between production steps. Testing should therefore reflect both transfer and any relevant hold period.
Other conditions to consider include:
tubing length and inside diameter;
the volume of fluid in contact with the tubing;
operating temperature;
flow rate;
formulation composition;
whether the tubing is new or has already been exposed to process fluid; and
the number and sequence of transfers.
These factors interact. A screening result from a short tube at room temperature should not automatically be applied to a longer production line with a different hold time.
Both subjects concern interactions between a fluid and its contact materials, but they answer different questions.
An extractables and leachables assessment investigates substances that may migrate from a contact material into the process fluid or drug product. A sorption assessment investigates whether a component of the fluid is reduced through interaction with a contact material.
A tubing grade can have relevant extractables data and still require a separate product-recovery assessment. Conversely, acceptable product recovery does not eliminate the need to evaluate extractables and leachables where applicable.
For pharmaceutical qualification, these are complementary lines of evidence—not substitutes for one another.
A useful study begins with a defined product requirement. Without a target concentration range or recovery criterion, it is difficult to decide whether an observed difference matters.
The following framework can help structure an application-specific assessment.
Identify what must be measured: the active ingredient, a preservative, a formulation component, or another critical substance. Use an analytical method appropriate to the expected concentration and study objective.
Measure the fluid before contact with the test assembly. The reference should be prepared and sampled in a controlled way so that variation in preparation or measurement is not mistaken for tubing-related loss.
Use the intended tubing grade and dimensions. Include a realistic length, connectors, and any other components that will contact the fluid if the objective is to assess the production assembly.
If the goal is specifically to investigate the tubing’s contribution, design comparisons that help separate its effect from that of other components.
Assess the applicable flow rate, temperature, and maximum contact or hold time. If fluid will pause in the line during normal operation, include that condition rather than testing continuous flow alone.
Take samples at defined times or positions in the process. Document the sampling containers and handling procedure: they, too, can affect the measured result.
Calculate recovery using the measured concentration before and after the defined contact condition:
Interpret the result alongside analytical variability and any changes observed in suitable controls. The pharmaceutical manufacturer should establish the acceptance criterion based on its product and process requirements.
Do not assume the tubing is responsible until other causes have been investigated. A lower measured concentration might involve sampling differences, product instability, filtration, other contact surfaces, or the analytical method.
If the evidence points to the tubing or fluid-path design, options to evaluate may include:
reducing tubing length;
reducing fluid hold time;
changing the sequence of process steps;
comparing alternative tubing materials or grades;
reviewing other high-surface-area components in the assembly; or
redesigning the fluid path to reduce overall contact.
Any proposed change should be tested in the complete process. A material that improves recovery may introduce different requirements for flexibility, connections, sterilization, or extractables assessment.
Suppliers can help identify candidate products and explain their manufacturing controls, but they usually cannot guarantee product recovery for an undisclosed formulation.
When discussing a sorption-sensitive application, provide as much relevant information as confidentiality permits and ask:
Which tubing grades are available in the required dimensions?
Are formulation-specific product-contact data available?
What tubing dimensions and manufacturing process are controlled?
Can representative production samples be supplied for testing?
Are material or process changes covered by change notification?
Is lot traceability available for qualification and production orders?
If prior recovery data are offered, check which substance, formulation, concentration, tubing geometry, and contact conditions were tested. Data from another application can guide screening, but they should not be treated as proof of performance in yours.
Assuming pharmaceutical suitability guarantees product recovery.
A general material designation does not predict how a specific formulation will behave.
Testing only the tubing when the finished assembly contains other contact materials.
Tubing-level comparisons are useful, but final process performance depends on the entire fluid path.
Ignoring the hold condition.
Product may spend longer in a filled line than it does moving through it.
Attributing every concentration change to sorption.
Analytical variation, sampling, instability, and other components must also be considered.
Using another drug’s test result as a pass for your formulation.
Sorption behavior is specific to the substance and test conditions.
Drug sorption in silicone tubing is not a universal problem, but it is a qualification risk worth examining when product concentration or dose recovery is critical.
The most reliable approach is to define the required recovery, test the proposed tubing and fluid path under representative conditions, and investigate any measured loss before changing materials. That gives pharmaceutical buyers a decision based on their own formulation and process—not on a broad claim about silicone tubing.
Some substances may interact with silicone tubing surfaces or move into the material under certain conditions. The extent depends on the substance, formulation, tubing, and contact conditions. Application-specific testing is needed to determine whether the effect is significant.
No. Sorption concerns a component of the fluid interacting with the contact material, potentially reducing its measured concentration. Leaching concerns substances migrating from the contact material into the fluid.
Compare measurements taken before and after contact with a representative tubing assembly under defined flow, temperature, and hold conditions. Include suitable controls and an analytical method appropriate to the component of interest.
Reducing the tubing’s contact area or fluid contact time may be worth evaluating, but the result depends on the application. Verify any design change through testing.
Supplier data can help select candidates and plan a study. Unless the data represent your formulation and conditions sufficiently, they should not be treated as a substitute for application-specific evaluation.
Yes, when the objective is to confirm process or product performance. Connectors, filters, containers, and other fluid-contact components can also affect measured recovery.
When product recovery matters, tubing selection should be supported by testing under your actual process conditions.
Contact Chensheng with your required tubing dimensions, fluid-path layout, operating temperature, and expected contact time. Ask about available tubing options and representative samples for your qualification study.
Send your project requirements to Chensheng to discuss a suitable silicone tubing solution.
