My institute is planning to acquire a SEC/FFF system with DLS, RI and MALS detectors. I've been looking at Wyatt systems and also for Postnova/Malvern.
Does anyone of you have experience with such systems? What are the major pros/cons of each one? Is any of these systems the one I should absolutely choose for the analysis of biologics/biosimilars, which might be our main focus?
Thanks for the help!
We have both MALS and DLS in the lab. We have a 8 detector Wyatt Heleos and ReX refractometer with a Shimadzu isocratic chromatography and UV detector that we have been running for a year and we are very pleased with it. Haven't been able to fool it yet. Some MALS systems can't cope with long, thin proteins but this one gives correct MWs with the most extreme proteins we have. Resolution of the protein peaks is essential so you have to invest in suitable analytical columns for the size ranges you are interested in. We use 10/300 Superdex 75 and 200, Superose 6 with 100ul samples. The smaller analytical SEC columns don't give you sufficient resolution with the protein concentrations needed to get a good light scatter signal.
We have an old Viscotek DLS. They were taken over by Malvern but this is the basis for their newer instruments. Demand for the DLS has grown as the size of recombinant proteins and their complexes as increased. Although it hasn't got great resolution it works well with heterogeneous samples with hydrodynamic radii greater than 10nm and it only needs 20ul of sample.
Wyatt sell a DLS detector, called QUELS, that can be incorporated into the MALS instrument but I think they work better as separate units i.e. you can look at very complex, high MW samples on the DLS that wouldn't resolve on the SEC MALS.
We have two Wyatt 18-angle MALLS systems. Both of them are Helios/rex sytems, and both are attached to Dionex bio-lc HPLC pumps. The way we have them set-up is one of them has the Wyatt viscostar attached and the other has a generic (Jasco) UV and the in-line QELS. I would not recommend putting the viscostar on a system that is to be used most of the time for routine mass measurements as it takes a considerable amount of time and patience to equilibrate the bridges. That being said it gives fantastic results.
I would thoroughly recommend the 18-angle detector coupled with the rEX, and the QELS whcih gives fantastic results and is easy to maintain yourself. It is easy to take the MALS chamber apart to clean the windows which we do on a regular basis. The Qels works fine, but you have to bear in mind that you will need slightly higher protein concentrations to get good data.
Important information is the quality of the pumps on the HPLC as bad pumps give wavy refractive index baselines, and the quality of the columns. They also need to be kept running all the time! I dont have any first hand experience with FFF but I have heard they are more trouble than they are worth. If you are using them for aggregation studies then I can understand getting one, otherwise stick with gel filtration and analytical ultracentrifugation. We also had a viscostar but this quickly found its way to the cupboard as the Wyatt systems were easier to use in our hands and if you dont need to balance the viscometer all the time it saves a lot of time and annoyance.
Hi to all,
does anybody have the experience with the W130i DLS system from Avid Nano?. I have asked about details and that was the reply:
"As you may have seen, the system is designed for both offline and online DLS and is especially sensitive for measurement of the smallest biological molecules. In fact the W130i has unbeatable sensitivity and performance for measuring hydrodynamic size, distribution and molecular weight of low concentration, low molecular weight molecules, aggregates, colloids and nano-particles.
The key features of the system are outlined below:
For your information, the current list price is 35,850 EUR for the complete system including software, installation and training. If you wish to use the system online, you will need to purchase a Chromatography Kit which includes an 8ul flow cell, an electronic signal conversion module and appropriate cable assemblies for your LC system (1,830 EUR). The only thing we ask you to supply is a PC with Windows XP or 7."
Now, I wonder, how would this instrument match with that from Wyatt or others you are using? We are not planning to acquire DLS/MALS just now, but in near future it may happen - and the price for this is much lower to Wyatt I would guess...? How about comparing on-line DLS to on-line MALS, i.e. direct measurement of size (+ extrapolation to mass) to direct mass measurement?
Dear David, Thomas and Ondrej,
Thank you all for your comments!
All the Best,