I think we can all generally agree that usually two is better than one: a bicycle is more efficient than a unicycle, two hands or minds are often better than one at completing tasks, etc. Does this translate though to Dual Liquid Chromatography (Dual LC)? The recent introduction of the Thermo Scientific™ Vanquish™ Duo UHPLC systems allows for the Dual LC hypothesis to be put to the test as this system allows three new workflows: Dual LC, Tandem LC or LC-MS and Inverse Gradients.
The Vanquish Duo allows true Dual LC due to the system containing a dual gradient pump and also a dual injection autosampler. When this is combined with two detectors then you essentially have two UHPLC systems in one and both flow paths are completely independent of each other, so you really can do two things at once. However, what benefits does a Dual LC approach bring? I will try and answer this in the remainder of this article.
Doubled Throughput:This is the most obvious benefit of a Dual LC approach. If you have one hundred samples, for example, you can run 50 samples on each flow path or channel in parallel rather than 100 samples per channel on a conventional (U)HPLC system. The benefit is that you double your throughput and finish in half the time without any loss of performance because, as stated above, these are two completely independent flow paths. An example of this increased throughput using Dual LC can be seen in this application note.
Increased Sample Knowledge:Personally, I think this is the real benefit of Dual LC. As the flow paths are independent of each other then it is possible to run two completely different analyses on your sample in parallel – if each analysis uses different thermostatting conditions, though, you will need a second thermostatted column compartment. A real life example of this is explained in this application note where the Vanquish Duo was used to perform both IEX chromatography of an antibody to assess charge variants and size exclusion chromatography for antibody aggregation in parallel. The possibilities here are almost endless, for example, comparing an originator and biosimilar drug side-by-side, assessing batch variability or as in this application note looking at both water and fat soluble vitamins in parallel.
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Additional Benefits:In addition to the doubled throughput and increased sample knowledge there are additional benefits to the Dual LC approach. With Dual LC you essentially get two UHPLC systems in one which means you are getting twice as much (throughput and knowledge) out of your single stack and footprint. One system is easier to maintain than two as well. There is also the argument that a Dual LC approach offers more reproducibility as the variables are reduced when everything is performed on a single system than over two independent systems. The biggest benefit, though, is that doubled throughput, increased sample knowledge and improved reproducibility all leads to increased productivity. Any why is productivity important? Because it allows you to reduce costs and lower the cost-per-sample.
The unique Dual LC approach generated by the Vanquish Duo offers numerous benefits such as increased sample knowledge and doubled throughput, all leading to increased productivity – why buy a conventional UHPLC system when you can get more productivity and flexibility in a single stack system? In addition the Vanquish Duo opens the possibility to do Tandem LC or LC-MS and Inverse Gradient workflows as well!