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Technical article for PRP users
How to Set PRP Centrifugation Correctly: RCF, RPM, Rotor and Time
In professional PRP preparation, tubes, anticoagulant or separation gel, centrifuge, rotor, runtime and handling all work together. Misunderstandings most often occur with RPM, RCF and time.
This guide explains the difference between RPM and RCF, shows conversion using rotor radius and provides technical orientation for reproducible PRP and PRF preparation.
RCF instead of RPM only
RCF describes the actual G-force acting on the sample and is more comparable across devices than RPM alone.
Consider rotor radius
The same RPM can generate different RCF depending on the rotor. The radius must therefore be considered.
Work system-specifically
Tube, rotor, RCF, time, brake setting and IFU must fit together.
RPM vs. RCF: why speed alone is not enough
RPM only describes how fast the centrifuge rotor rotates. For the sample, the actual relative centrifugal force is decisive: RCF or G-force.
Two centrifuges can run at the same RPM and still generate different forces because rotor radius differs. An instruction such as “3,000 RPM for 10 minutes” is therefore only transferable to a limited extent without rotor radius.
- RPM
- rotor radius
- RCF / G-force
- rotor type
- runtime
- tube and protocol
The RCF formula: converting RPM into actual G-force
Relative centrifugal force can be calculated with the following formula:
RCF = 1,118 × 10⁻⁵ × r × RPM²
RCF = relative centrifugal force in × g, r = rotor radius in centimetres, RPM = revolutions per minute. If a protocol specifies 1200 × g and the rotor radius is about 8.6 cm, the speed is approximately 3,500 RPM.
Practical note: calculate RCF/RPM directly with the tool
To avoid manual conversion, you will find a separate RCF/RPM conversion tool directly below this article. There you can enter the rotor radius of your centrifuge and calculate the suitable RPM for a desired RCF or G-force.
The tool is intended as mathematical orientation and does not replace the instructions for use of the medical device, the centrifuge manual or the professional assessment of the user.
Rotor type: fixed-angle and swing-out rotors
In addition to RPM and RCF, rotor type influences layer formation and handling after centrifugation. Fixed-angle and swing-out rotors produce different sedimentation geometries.
Neither rotor type is automatically better. The decisive point is whether rotor, tube, RCF, time and manufacturer protocol fit together.
- fixed-angle rotor: compact and common in benchtop centrifuges
- swing-out rotor: horizontal orientation during the run
- adapters, buckets and tubes must match the device
Runtime, brake and soft stop: avoid unnecessary layer disturbance
Runtime should never be considered in isolation. A protocol with lower RCF and longer runtime can produce a different result from one with higher RCF and shorter runtime.
After centrifugation, blood components are separated into layers. If device and protocol allow it, gentler braking may help keep the layer image calm.
- choose brake setting according to device manual
- remove tubes calmly and vertically
- avoid strong shaking
- do not unnecessarily tilt or mix separation-gel systems
Single-spin or double-spin: decide system-specifically
With single-spin, preparation takes place in one centrifugation run. This is often used in defined PRP systems, especially with tubes containing anticoagulant and separation gel.
With double-spin, the sample is processed in two centrifugation steps. Whether this is useful depends on system, desired PRP type and manufacturer or protocol specification.
Example Vi PRP-PRO: think in RCF, not only RPM
Vi PRP-PRO is often used in practice with a defined single-spin protocol. The decisive value is not RPM alone, but the target RCF.
If the product protocol specifies 1200 × g for 7 minutes, the suitable RPM must be calculated using the rotor radius of the centrifuge.
Orientation values for PRP and PRF: use only system-specifically
The following information is not a general treatment recommendation. It only shows that PRP and PRF protocols can vary significantly depending on the system.
| Protocol type | Typical view | Important note |
|---|---|---|
| PRP with separation gel, e.g. Vi PRP-PRO | defined single-spin according to product protocol | RCF, time and tube must fit the manufacturer protocol |
| PRP without separation gel | often system-dependent, sometimes single- or double-spin | no blanket transfer of external RPM values |
| PRF / PRF-related protocols | often without anticoagulant and without separation gel | time-critical because clotting starts immediately |
| Double-spin PRP | two centrifugation steps possible | use only if protocol and product provide for it |
Especially with PRF, tubes without anticoagulant must be processed immediately after blood collection. Time, temperature, tube material and centrifuge are closely linked to the protocol.
Temperature and device location: practical, but do not improvise
Centrifuges can warm up during longer use. Temperature conditions should not be improvised, but should follow the device manual, tube information and protocol.
Precooled adapters, opened lids or other measures should not be recommended generally. Safe and intended centrifuge operation remains decisive.
- do not operate in direct sun or next to heat sources
- ensure sufficient ventilation
- observe manufacturer information on duty cycle
- use adapters and buckets only as intended
Common mistakes in PRP centrifugation
Typical mistakes include copying RPM values without rotor radius, mixing PRP and PRF protocols or using unsuitable adapters and tubes.
Experience can be helpful, but it does not replace IFU, device manual and intended purpose of the product used.
- copying RPM without rotor radius
- mixing PRP and PRF protocols
- not matching tube and centrifuge
- replacing manufacturer information with experience
RCF / RPM
| RCF | Radius | RPM |
|---|---|---|
| 1200 × g | 8.0 cm | approx. 3,660 RPM |
| 1200 × g | 8.6 cm | approx. 3,530 RPM |
| 1200 × g | 9.0 cm | approx. 3,450 RPM |
| 1200 × g | 10.0 cm | approx. 3,275 RPM |
Check question
| Check question | Why important? |
|---|---|
| Is the target RCF known? | RCF is more comparable across devices than RPM. |
| Is the rotor radius known? | Without radius, RPM cannot be correctly converted into RCF. |
| Does the tube fit the rotor? | Length, diameter and adapters must be compatible. |
| Are tubes correctly balanced? | Important for device safety and smooth running. |
| Is the brake setting suitable? | Excessive braking can influence the layer image. |
| Is the IFU followed? | Manufacturer information is decisive. |
Conclusion: always consider RCF, RPM and time as one system
Professional PRP centrifugation is not just pressing a button. It is a standardised process in which tube, centrifuge, rotor, RCF, RPM, runtime and handling must fit together.
The most important step is moving from RPM-only thinking to understanding actual RCF or G-force. Only then can protocols be technically transferred between different centrifuges in a traceable way.
FAQ
FAQ: PRP centrifugation, RCF and RPM
What is the difference between RPM and RCF?
RPM describes rotor speed in revolutions per minute. RCF describes the relative centrifugal force, the actual G-force acting on the sample.
Why is RPM not enough for PRP?
An RPM value is not clear without rotor radius. Two centrifuges can create different RCF values at the same RPM.
How do you calculate RCF from RPM?
The formula is: RCF = 1.118 × 10⁻⁵ × r × RPM², where r is the rotor radius in centimetres.
Which RCF is suitable for Vi PRP-PRO?
The product protocol is decisive. If 1200 × g for 7 minutes is specified, the suitable RPM must be calculated using rotor radius.
Is a fixed-angle or swing-out rotor better for PRP?
This cannot be answered generally. Both can be suitable if centrifuge, tube, adapter, RCF, time and protocol fit together.
Can PRP protocols be transferred from one centrifuge to another?
Only with conversion and checking. RCF, rotor radius, rotor type, tube, filling volume, time and manufacturer information are decisive.
Note for professional users: This article provides technical information about the physical principles of centrifugation. The instructions for use of the medical devices used, the centrifuge manual, the manufacturer’s intended purpose and professional assessment remain decisive.
