I spill a lot of digital ink extolling the virtues of our OMNISEC system, and for good reason!  The power of a complete, advanced detection SEC system is undeniable.  But in this post, I’m going to focus on a single, modular detector that can fit almost anywhere due to its versatility: the SEC-MALS 20. 

What is it?

The SEC-MALS 20 is a multi-angle light scattering (MALS) detector that can provide absolute molecular weight data.  It is a modular detector, about the size of a large shoebox, and can pair with any existing SEC system.  Almost all aqueous and organic mobile phases are compatible with the unit, allowing it to analyze just about every kind of macromolecular sample.

What data does it offer?

The twenty detectors of the SEC-MALS 20 observe the intensity of light scattered by the sample at various angles.  This data is combined with concentration information (from a RI or UV detector) and plotted in a specific manner for two reasons.  Firstly, to extrapolate the data to determine the scattered light intensity at the zero angle, from which the absolute molecular weight is calculated.  Secondly, to determine the initial slope of the plot which is related to the radius of gyration (Rg) of the molecule.

SEC-MALS 20 & OmniSEC v5 software

Who needs it?

If you have an existing SEC system and want to upgrade your molecular weight data, the SEC-MALS 20 is perfect!  Not only will you increase the accuracy of your calculations, but it has the added benefit of eliminating the need to generate a calibration curve.  Do you need to know if your sample contains aggregates or high molecular weight species?  The presence of a SEC-MALS 20 with your system can offer valuable insight.  Additionally, if you want to measure molecular size, adding the MALS detector offers the calculation of Rg.  Furthermore, do your samples absorb at higher wavelengths?  To that end, we offer a SEC-MALS 20 with a narrow band filter to minimize the chances of absorption skewing your data.  Finally, maybe you simply prefer MALS to the right-angle & low-angle light scattering detector configuration.  

How will it connect to my system?

The SEC-MALS 20 can incorporate both a RI and a UV signal (single wavelength) from your existing system.  The output, along with the MALS signals, are recorded and analyzed by the OmniSEC v5 software.  You will use your current software to control the pump and autosampler.  To ensure you are capturing the data correctly, you will need to replicate the sample sequence in the OmniSEC v5 software, too.  If you are using Waters’s Empower software, you can conveniently import the sequence to OmniSEC v5.  A trigger connection allows the sequence to run uninterrupted once initialized. 

In addition, if you’re interested in a complete GPC/SEC system with MALS, the SEC-MALS 20 can join seamlessly with OMNISEC.  The unit sits on top of OMNISEC REVEAL and inserts into the flow path using simple fluidic connections.  Its signal is integrated into the OMNISEC v10+ software for data acquisition and processing.  The images below show the hardware and software of a combined system.

SEC-MALS 20 with OMNISEC hardware and software

Do you have any Application Notes?

Yes!  The list below contains application notes highlighting the SEC-MALS 20.  You can also find these, and more, through our Knowledge Center

Why should I choose the SEC-MALS 20?

And for good measure, here are two technical notes that describe the benefits of the SEC-MALS 20 and offer evidence to back up those claims. If you’re working within a budget, we offer a SEC-MALS 9 detector that includes, as you probably guessed, nine angles instead of twenty.

What does it look like in action?

The two homemade videos below offer a glimpse of how easy and powerful working with SEC-MALS 20 data is.  Firstly is a demonstration of using SEC-MALS with a UV detector.  I use a BSA sample to create a method and then apply it to a lysozyme sample.

Secondly, a colleague works through the analysis of a polystyrene sample showing angular dependence.  As can be seen, she highlights the various MALS-specific plots, data, and options available.

Final thoughts

So what are you waiting for?  Whether you have an existing system with or without detectors or are seeking to acquire a complete system, the addition of the SEC-MALS 20 upgrades your analysis options!

In conclusion, I hope the information presented here demonstrates the versatility of the SEC-MALS 20.  Furthermore, if you have any questions about the detector, please don’t hesitate to contact us or email me directly at

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