Teflon Fittings Pipetting Head

Why understanding 24, 96, and 384 channel specifications is so important!

INTEGRA’s Method for Calibrating VIAFLO 96/384 Pipetting Heads

INTEGRA uses a hybrid gravimetric/photometric method of calibration for the VIAFLO 96/384 pipetting heads (ISO IWA15:2015 Method B.6). One channel is tested gravimetrically (3 test volumes, 5 measurements each). This channel is determined to be within the accuracy and precision specifications, and then used as a reference channel. All channels are then measured using a photometric method and compared to the reference channel. Calculated accuracy and precision for the entire pipetting head must be smaller than or equal to INTEGRA stated specifications. The precision (CV) is defined as channel-to-channel variation within the pipetting head. All channels of INTEGRA’s pipetting heads (24, 96, and 384) are individually measured and assessed, and no outliers are allowed.

Other Methods for Calibrating 24, 96, and 384 Channel Instruments

While there are many other methods used to calibrate 24, 96 or 384 channel instruments, many other manufacturers use methods which rely on gravimetric-only measurements. For example, all 96 or 384 wells are filled with a target volume, and the entire plate is weighed (ISO IWA15:2015 Method B.4). An average volume is then calculated for each well – this process may be repeated multiple times to obtain a precision (CV) value. An average of these dispenses is obtained and determined to be within specification or not. Others still will perform a similar gravimetric-only method, but only on randomly selected channels – often between 5 and 20 channels. Again, an average of these dispenses is obtained and determined to be within specification or not.

Why the INTEGRA Calibration Method is Preferable to Others?

Many other manufacturers of 24, 96 or 384 channel pipettes only measure their instruments gravimetrically by weighing the full plate and simply calculating an average dispense per well. A disadvantage of this method is that outliers, such as defective channels, are not detected. The mean of 24, 96 or 384 channels does not show outliers, let alone identify which channel is affected. In most cases, individual channels are not tested.

The INTEGRA method gives more information about the pipetting head and each individual channel, since data is obtained for every channel. The calibration pass/fail decision is based on both the whole plate, as well as individual channel results. This method is better at identifying channels which perform poorly.

Other manufacturers method

Other manufacturer's methods: If 7μl is the desired dispense, and every channel is not checked individually, this plate would pass calibration - not good!

INTEGRA's method

INTEGRA's method: If 7μl is the desired dispense, every channel must deliver +/- 7μl to pass calibration.

In addition, the INTEGRA method can be considered closer to results expected in laboratories, since photometric measurements mimic real lab working conditions – mixing liquids, working with two different types of liquids, etc. Gravimetric measurements are based on a dry dispense (a dry plate). Therefore, the results of INTEGRA’s calibration procedure will likely be closer to every-day results obtained in most labs.

VIAFLO 96/384 Specifications vs. Other Manufacturers of 24, 96, and 384 Channel Pipetting Instruments

INTEGRA specifications are designed to be achievable in most laboratories. Other manufacturers of 96/384 channel pipetting instruments may state superior specifications, but testing of those instruments in a typical lab setting has proven this to not always be achievable. Two VIAFLO 96 channel pipetting heads were tested for accuracy/precision, and two 96 channel instruments from other manufacturers were also tested. The instruments were all tested in a non-climate controlled lab setting. The INTEGRA VIAFLO pipetting heads were tested according to the INTEGRA method, while the other manufacturers were tested both according to the INTEGRA method, as well the manufacturer’s own gravimetric-only method.

VIAFLO Pipette Head Test

Method: INTEGRA gravimetric/photometric hybrid, 10% of nominal volume

VIAFLO 96 with 300 µl channel head

*(sn: 52902)

Volume
(µl) 

Tip Size
(µl)

Manufacturer Accuracy Spec %

Measured Accuracy is within spec

Manufacturer Precision Spec % CV

Measured Precision is within spec

30

300

2.5

YES

1.5

YES

VIAFLO 96 with 12.5 µl channel head

*(sn: 52868)

Volume
(µl) 

Tip Size
(µl)

Manufacturer Accuracy Spec %

Measured Accuracy is within spec

Manufacturer Precision Spec % CV

Measured Precision is within spec

1.25

12.5

8

YES

3

YES

Result of VIAFLO Pipette Head Test

VIAFLO specifications have been made to be realistic and reachable by most pipetting personal and under normal laboratory conditions, and the results of the test prove this.

Other Manufacturer Test

Method: INTEGRA’s gravimetric/photometric hybrid

96 Channel Instrument: Other Manufacturer 1 

(Nominal Volume: 300 µl)

Volume
(µl)

Tip Size
(µl)

Manufacturer Accuracy Spec %

Measured Accuracy is within spec

Manufacturer Precision Spec % CV

Measured Precision is within spec

50

50

2

YES

3

YES

2

50

2

NO (> 10%)

3

YES

1

50

2

NO (> 15%)

3

YES

96 Channel Instrument: Other Manufacturer 2 

(Nominal Volume: 300 µl)

Volume
(µl) 

Tip Size
(µl)

Manufacturer Accuracy Spec %

Measured Accuracy is within spec

Manufacturer Precision Spec % CV

Measured Precision is within spec

300

300

1

YES

1

YES

30

300

1.5

YES

1

YES

15

300

2

NO (> 2%)

2

YES

5

300

5

NO (> 7%)

5

YES

Other Manufacturer Test

Method: Manufacturer’s gravimetric-only method

96 Channel Instrument: Other Manufacturer 1

Volume
(µl) 

Tip Size
(µl)

Manufacturer Accuracy Spec %

Measured Accuracy is within spec

Manufacturer Precision Spec % CV

Measured Precision is within spec

50

50

2

YES

3

YES

2

50

2

NO (> 10%)

3

YES

1

50

2

NO (> 15%)

3

YES

96 Channel Instrument: Other Manufacturer 2 

Volume
(µl) 

Tip Size
(µl)

Manufacturer Accuracy Spec %

Measured Accuracy is within spec

Manufacturer Precision Spec % CV

Measured Precision is within spec

300

300

1

YES

1

YES

30

300

1.5

YES

1

YES

15

300

2

NO (> 2%)

2

YES

5

300

5

NO (> 7%)

5

YES

Result of Other Manufacturer Test

The other manufacturer’s instruments have defined a specification at low volumes which was not reached through testing. They promise a performance of the pipetting instrument which is very difficult to achieve, especially when pipetting low volumes using tips which contain a large amount of dead air space relative to the pipetted volume.

Conclusion

While only a small number of instruments were tested, similar results can and should be expected from other instruments – INTEGRA’s, as well as other manufacturers. The VIAFLO 96/384 pipetting heads are manufactured using specifications which are attainable in labs with stable environmental conditions, and by lab personal following good pipetting practices. In addition, the results generated using the INTEGRA method gives more information about the pipetting head, and should be considered to be closer to daily-use results generated when compared to other, less descriptive methods (Gravimetric only, for example).

Questions You Should Ask About all 96/384 Channel Specifications

Comparing specifications of different 24, 96 or 384 channel instruments can be a useful tool in beginning to understand the differences between the instruments. However, when comparing specifications, the following questions should be asked:

What is the method used by this manufacturer to determine if an instrument passes or fails calibration?

Does the manufacturer use a method compliant with an international standard which produces results for individual channels? Be very wary of gravimetric only methods, and methods which do not test every channel.

Do the manufacturer’s specifications promise unrealistic expectations of everyday users?

Example: When pipetting 10% or less than the total tip volume, specifications of Accuracy 2% or better and Precision (CV) 1% or better should be considered very difficult to achieve in normal lab settings.

VIAFLO 96/384 Pipetting Heads Specifications

Users can simply change the pipetting head of their VIAFLO 96 and VIAFLO 384 to guarantee optimal matching of the available volume range to the application performed. Changing a pipetting head of VIAFLO 96 and VIAFLO 384 is easy and takes less than one minute.

Each channel of a pipetting head is independent, having its own precise piston and sealing to exclude any cross-channel influences for error-free pipetting.

VIAFLO 96/384 Pipetting Heads Specifications

VIAFLO 96/384 96 channel pipetting head
Easily interchangeable pipetting heads, allowing you to switch between 24, 96 and 384 channel pipetting to suit your application

Download

Specification Statement VIAFLO 96/384 as PDF