When you are in the process of developing any new analytical technology, having the ability to prove your innovations are as precise and as accurate as you believe them to be is critical. This need for external verification is true whether you are involved in the development of a new protocol, a new assay or a new instrument.
It can be devastating to find out that well before your new invention has reached its limits, the techniques you have access to for testing it have become useless.
This frustrating situation was faced by Mark Wardle, development engineer at SGE Analytical Science, who was involved in creating the award winning eVol® – the world’s first digitally-controlled analytical syringe. The eVol is a marriage of two precision devices: a digitally controlled and programmable electronic drive and an XCHANGE® enabled analytical syringe.
The aim of the project was to develop an instrument that could accurately deliver a requested volume time after time no matter who was operating the device – unlike pipettes where poor operator technique can lead to large variations in the actual volumes delivered.
The eVol more than met the expectations of the development team in reducing the variability of volumes dispensed when different operators attempt the same volume transfer. What’s more, it was also suitable for transferring non-aqueous, viscous and hazardous liquids. The eVol can be fitted with a number of different XCHANGE enabled syringes allowing it to dispense volumes from 1mL down to 200nL.
However, when Wardle was preparing the eVol specification document, he found he couldn’t complete it as he wasn’t able to generate the accuracy and precision data – that is, the proof of performance – he needed at the lower end of the eVol’s dispensing range. While Wardle found that gravimetric analysis of dispensed volume worked for volumes greater than 50 µL, when he attempted to go below this volume this traditional method for measuring volumes did not provide the results he expected.
No matter what he did with the SGE facility’s air conditioning system, the water he was delivering onto the analytical balance evaporated before a stable reading could be accurately determined. In the end, he tried five different gravimetric methods – but nothing worked.
Due to SGE’s expertise in chromatography, Wardle’s team then attempted to use a chromatographic technique to test the eVol’s accuracy. A known volume of an internal standard was added to a test mix, and then dispensed from the eVol. The concentration of the internal standard was then measured via gas chromatography and the accuracy of the eVol calculated. This was time consuming and wasn’t sufficiently accurate. After weeks of trying to develop a chromatographic methodology to a suitable degree of accuracy, the team stopped using this approach and looked around for a technique that they could use to determine the eVol’s accuracy at low volumes.
Next, they explored using a colorimetric method, but efforts were quickly discontinued when they discovered that the plate reader demonstrated an inaccuracy of ±2% – much larger than what the team predicted the inaccuracy of the eVol to be.
Then SGE turned to a fluorescence spectrophotometry method, but despite technical assistance from the instrument manufacturer, their efforts again yielded inadequate confidence in proving the eVol’s performance claims.
All the while, Glenn Clivaz, Director of SGE’s Liquid Handling Business Unit was pushing for data for the specifications document, so that they could launch the eVol and make as many waves in the market as possible.
Despite not having all the data they wanted for the specifications document about the eVol, SGE decided to exhibit their new innovation at Lab Automation 2010 in Palm Springs, CA, before its official launch. While at the show, Clivaz, discovered the Artel PCS® Pipette Calibration System and asked if he could use it to test the eVol – Artel went one better and offered to put a PCS at the SGE booth. To the amazement of the SGE team they could demonstrate the eVol’s claimed precision and accuracy in the exhibition hall –at smaller volumes than Wardle had been able to verify in the SGE labs in Australia.
“The visitors to the booth loved it,” said Clivaz, “They got to play with a great new liquid handling instrument, and because the PCS was so user friendly and scientifically robust, they could test the eVol’s accuracy and precision right at the booth – what’s more they were all getting reliable results!”
The PCS uses Ratiometric PhotometryTM, an innovative application of the Beer-Lambert law which measures the ratio between the light absorbed by a blue dye at 730nm and a red dye at 520nm. This data is then used to calculate the accuracy and precision of volumes dispensed from the liquid handling device.
This ratiometric measurement can accurately determine volumes down into the nanoliter range without needing the controlled environment required for gravimetric analysis – as shown by Artel’s ability to investigate pipette performance in some of the most inhospitable environments in the USA during its Extreme Pipetting Expeditions.
Clivaz was so impressed by the PCS that he wanted to take the instrument back to Australia with him so that Wardle could use it to validate and improve the specifications for the eVol. Artel’s Vice President of Sales, Barry Godowsky was so confident the PCS would enable SGE to finish their specifications document that he happily let Clivaz take a PCS from the booth with him on a sale or return basis. However, Australian customs had other ideas and Clivaz was thoroughly questioned about the PCS instrument as he had brought almost no documentation with him from the show. After a gruelling 3 hours, Clivaz emerged from the customs hall, with PCS in hand.
The next day, Clivaz brought Wardle a present that he would forever remember, and one that would help the eVol win one of the most coveted awards a technology company can win – an R&D100 award. These awards carry so much prestige they are often called the Oscars of Innovation.
On receipt of the PCS, Wardle immediately got to work setting up the system and started getting solid results straight away. He found the PCS very easy to set up and use – he didn’t even need to read the manual, he admits. He was easily able to validate the expected eVol specifications and these were added to the eVol manuals and launch documents.
According to George Rodrigues PhD, Artel’s Senior Scientific Manager, the performance of the eVol is excellent, with the relative inaccuracy of the device at the full-scale values of 500µL, 50µL and 5µL consistently measuring within 0.1%. However, Rodrigues was most impressed with the accuracy and precision with which the 5µL eVol could dispense 0.2µL (200nL): the eVol attained a relative inaccuracy of just 0.41% and a coefficient of variation (%CV) of just 0.71% – this equates to a combined standard deviation for the eVol and the PCS measuring system approaching 1nL .
“Artel has always believed that the PCS was capable of measuring 0.2µL with a standard deviation of 1nL or better, but these were always based on theoretical considerations,” said Rodrigues. “Now that the SGE eVol has been invented, we have the capability of directly demonstrating %CV measurement capability at the 1nL level using an actual liquid delivery device. It’s the perfect marriage of precise liquid delivery and precise liquid measurement.”
To put these numbers into perspective, one of the leading providers of gravimetry-based pipette calibration services, Rainin, quotes a “best uncertainty” of 14nL for a 0.2µL pipette – even under the carefully controlled conditions employed at the Rainin Headquarters in Oakland, California.
The PCS has now become integral to SGE’s further development of the eVol platform and has been used extensively in the development of the latest line extension – a 1mL version that has been requested by many scientists in the NMR field as well as those conducting assays approved by the US Food and Drug Administration (FDA).
Following on from the massive success that SGE had with the PCS, SGE asked Artel to deliver a Liquid Handling Quality Assurance Seminar to train staff in proper manual pipetting technique and assist them in their quest to gain ISO17025 compliance standards.
Doreen Rumery, Artel’s Quality Control Manager, made the 50 hour trip from Portland, Maine in the US to Melbourne, Australia to provide the training sessions. While she was able to provide lots of insight into how the SGE personnel could improve their performance when using standard manual pipettes, she also was amazed at the performance of the eVol.
“Seeing the eVol in action for the first time was a mind-blowing experience. Not only was it so easy to use, but the accuracy the users were getting with it were phenomenal,” said Rumery. “All of the SGE personnel were easily able to get gold medals in our Pipetting Olympics competition using the eVol – something I have never seen before.”
During her visit, Rumery also provided guidance on the steps SGE needed to follow to gain ISO 17025 accreditation so the company can provide its customers with calibration services straight from the factory. Those services would make use of the PCS technology so that all calibrations are traceable to the International System of Units (SI) via top laboratories such as the US National Institute of Standards and Technology (NIST) and the UK National Physical Laboratory (NPL) which further verifies SGE’s claims about the eVol.
“Having access to the PCS gives our sales teams extra confidence in the claims we make about the eVol being the most accurate and precise liquid delivery system on the market,” added Clivaz. And because the Artel technology is so well known and respected, Mr. Clivaz says that SGE is considering putting PCS instruments in all its global sales offices so that customers can test the accuracy and precision of the eVol for themselves.