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Daniel Some, PhD, is director of marketing and principal scientist, at Wyatt Technology Corporation, 6300 Hollister Ave, Santa Barbara, CA 93117-3253.

Articles

The macroscopic properties of material based on poly(D,L-lactic-co-glycolic acid) (PLGA) polymers are tunable by molar mass distribution and degree of branching, enabling optimization for applications in the pharmaceutical and medical industries. Size-exclusion chromatography followed by online multi-angle light scattering with intrinsic viscosity detection (SEC–MALS–IV) is an advanced analytical method for determining absolute molar mass distributions, identifying polymer conformation and quantifying branching. SEC–MALS–IV overcomes the errors that can be encountered in molar mass determined by conventional SEC, which arise from chemical composition and molecular structure, and provides comprehensive characterization of PLGA to facilitate the targeted development of optimized polymer.

Molecular Structure of Poly(Lactic-co-Glycolic acid) by SEC with Advanced Detection

Water-soluble macromolecules require water as a mobile phase, and method development therefore seems to be straightforward. At second glance, however, aqueous gel permeation chromatography/size-exclusion chromatography (GPC/SEC) is complex and the choice of the stationary phase and pH are crucial. In addition, mobile phase additives are often required to allow for interaction-free separations.

Tips & Tricks GPC/SEC  Aqueous GPC/SEC for Water-Soluble Macromolecules

The chemistry of samples analyzed using gel permeation chromatography/size-exclusion chromatography/gel filtration chromatography (GPC/SEC/GFC) is very diverse. Different chemistries of stationary phases are required to allow for true size separation. Several types of materials are available, all of which have their advantages and limitations. While silica‑based stationary phases are most common in high performance liquid chromatography (HPLC), for macromolecules polymer-based phases are popular.

Tips & Tricks GPC/SEC: Silica Versus Polymer‑Based Columns

The “greenest solution” is certainly using no solvent but gel permeation chromatography/size-exclusion chromatography (GPC/SEC) as a liquid chromatography (LC) technique requires the use of a mobile phase. The growing awareness of the need for more sustainable (greener) solutions has focused attention on environmentally- and health-friendly solvents and solutions.

Tips & Tricks GPC/SEC: “Green” GPC/SEC and Solvent Alternatives

The accuracy of a measurement describes how close the measured result is to the true value. Accuracy is influenced by systematic errors, which are difficult to detect even for experienced scientists.

Tips & Tricks GPC/SEC: Systematic Errors in GPC/SEC/GFC

One of the major problems with plastics is recycling. Only a few materials can be recycled and the acceptance of recyclates is sometimes low. GPC/SEC can be applied to investigate the quality of materials containing recycled portions.

Tips & Tricks GPC/SEC: How GPC/SEC Can Help to Reduce PET Plastic Waste

PSS Polymer Standards Service GmbH, Mainz, Germany.

The addition of a light scattering detector dramatically increases the capabilities of gel permeation chromatography/size-exclusion chromatography (GPC/SEC) analysis. However, the complexity of the system also increases. This instalment of Tips & Tricks discusses column issues when working with light scattering detectors.

Tips & Tricks GPC/SEC: Column Issues with Light Scattering Detectors

Although modern GPC/SEC instruments are generally very reliable, scientists sometimes encounter problems. This instalment of GPC/SEC Tips & Tricks offers advice on how to efficiently identify the root cause of problems, such as dealing with a too high pressure, loss of resolution, or drifting baselines.

Tips & Tricks GPC/SEC:  What You Need to Know to Allow for Efficient GPC/SEC Troubleshooting

The most commonly applied detector in gel permeation chromatography/size-exclusion chromatography (GPC/SEC) is the differential refractive index detector, RI. How UV–vis detection, if applicable, adds true value to GPC/SEC applications is discussed in this instalment of Tips & Tricks. 

Tips & Tricks GPC/SEC: UV–vis Detection

The potential of TD SEC for in situ analyses of thermoreversibly bonded polymers is discussed. TD SEC allows the evolution of the polymer’s molar mass distribution to be monitored during temperature-sensitive bonding and debonding reactions. Through quantitative evaluation of the chromatograms, the reaction-influencing parameters can be studied, which is crucial for the effective development of novel functional materials. By using TD SEC, the effect of polymer size and flexibility on the debonding temperatures of DA polymers was confirmed, their debonding and bonding ability studied, and the de-crosslinking of thermoreversibly cross-linked DA polymers assessed. TD SEC offers a versatile platform for a broad variety of different polymer materials and to assess a variety of different analytical questions.

Size-Exclusion Chromatography (SEC)