SANTA BARBARA, CALIFORNIA (June 18, 2008) – Wyatt Technology, the world leader in absolute macromolecular characterization products, announces the publication of a new application note demonstrating the capability of its DAWN Multi-Angle Light Scattering (MALS) and Optilab rEX (refractive index detector) to achieve rapid, automated molecular characterization via a Zimm plot experiment. Coupled to a binary HPLC pump and Wyatt’s powerful ASTRA software, the DAWN and Optilab rEX provided accurate light scattering data and expedited results.

Historically, a syringe pump was used to prepare, mix and sequentially inject five or more sample concentrations required for a standard Zimm plot. The solutions had to be prepared prior to the experiment and entered by hand.Overall, this was an intensive and time-consuming procedure. Additionally, air was often inadvertently injected into the detectors, resulting in large noise spikes in the data. A binary HPLC pump was used in conjunction with the Optilab to automatically determine the concentrations during the experiment. The differential refractive index values corresponding to the concentrations of the solutions are collected by ASTRA, eliminating the need to determine the concentrations a priori.

For this particular application, a ~545kDa Dextran natural polymer was dissolved at 2.5 mg/mL in buffer and placed in a reservoir, whereas buffer alone was placed in a separate reservoir. A low volume 0.45 mm filter was installed between the binary HPLC pump and a DAWN HELEOS multi angle light scattering detector (Wyatt). The Optilab rEX was installed downstream of the light scattering detector. The flow rate was set to 1 mL/min and the pump was set to deliver a concentration series of 0% A to 100% A and then back to 0% A. Each concentration was run for three minutes for a total of 3 mL per step. This volume ensured that a plateau was attained in both the static light scattering and the concentration detector. With plateauing, identical concentrations were present in both detectors. The results of the experiment clearly demonstrated that automated sample dispensing and concentration detection ensure clean data acquisition, enabling accurate detection of the molar mass, size and second virial coefficient in fewer than 30 minutes.Data quality was found to exceed that of standard syringe pump runs.

For more information on Wyatt Technology’s Optilab rEX refractive index detector and ASTRA software or to obtain a copy of this application note, please visit www.wyatt.com or e-mail info@wyatt.com