Field-flow fractionation hyphenated techniques

The follow-up section will deal with separation methods based upon (a) molecular size and related to it hydrodynamic volume (size-exclusion chromatography and ultrafiltration), (b) molecular size and related to it molecular diffusivity (field-flow fractionation), and (c) charge/size ratio and related to it molecular polarity (electrophoresis and mass spectrometry). Also reviewed will be hyphenated techniques or those that combine separation by chromatography or electrophoresis with spectral detection. 

Schimpf ME (1995) Determination of molecular weight and composition in copolymers using thermal field-flow fractionation combined with viscometry. In Provder T, Barth HG, Urban MW (eds) Chromatographic characterization of polymers hyphenated and multidimensional techniques. American Chemical Society, Washington, DC, pp 183-196... 

This book covers some of the significant advances in hyphenated chromatographic separation methods for polymer characterization. Chromatographic separation techniques in this volume include size-exclusion chromatography, liquid chromatography, and field flow fractionation methods that are used in conjunction with information-rich detectors such as molecular size-sensitive or compositional-sensitive detectors or coupled in cross-fractionation modes. 

Cledat, D., Battu, S., Mokrini, R., and Cardo, P. (2004). Rice starch granule characterization by flow cytometry scattering techniques hyphenated with sedimentation field-flow fractionation. J. Chromatogr. A 1049(1-2), 131-138. 

Jeon, S.J. Schimpf, M.E. Cross-fractionation of copolymers using SEC and thermal field-flow fractionation for determination of molecular weight and composition. In Chromatography of Polymers Hyphenated and Midtidimensiorud Techniques, Provder, T., Ed. ACS Symposium Series No. 731, Ch ter 10 ACS Publications Washington, DC, 1999 141-161. 

Continued improvements in FFF instrumentation, refinements in technique and hyphenation with detectors such as MALLS have broadened the application of this method and effectively elevated it from the status of possibly useful technique to a reliable applied research tool for assessing the size and shape of wheat proteins. For additional reading concerning FFF theory, principles, and applications, the reader is referred to other sections of this encyclopedia as well as to Field-Flow Fractionation Handbook edited by Schimpf et al. A review of the application of FFF to wheat protein analysis can also be found in Preston and Stevenson. 

Keywords Crystallization analysis fractionation Field Flow Fractionation High performance liquid chromatography Hyphenated techniques Liquid chromatography Polyolefin analysis SEC-NMR coupling Size exclusion chromatography Temperature rising elution fractionation Two-dimensional liquid chromatography... 

Chapters on sample introduction and hyphenated sample treatment and ICP systems have also been further updated since the last edition. No doubt that chromatographic, electrophoresis, flow injection and field flow fraction separations have extended ICP-MS (and AES) measurements as the mainstay of elanental specia-tion measurements in biological and environmental fields. Without the combination of these separation techniques and ICP measurements, elemental speciation applications would be severely hampered... if not impossible (Chapter 18). The ability to measure P and S with high sensitivity has opened up new opportunities in proteomics, for example. Species-specific and unspecific isotopic dilution (ID-MS) has been critical in quantifying speciation analysis and revealing recovery errors (Chapter 13). Species-specific techniques have been applied to identify species transformations, resulting in the development of multi-species methods whereas, hyphenated species-unspecific ICP-ID-MS determinations of heteroatoms such as sulfur have become a common quantification technique in proteomics. 

LC/NMR in various combinations with LC/UV-DAD, LC/MS, LC/MSMS, LC/IR, and/or LC/CD has been used in many applications related to the online identification of natural products. In this field, the challenge for hyphenated techniques is important since often the characterization of completely unknown molecules is required in very complex biological matrices. In this case, LC hyphenated techniques are used for the chemical evaluation of biologically active fractions or extracts and for dereplication purposes. As full structure assignment is often needed, all online spectroscopic data are taken into consideration. Most applications are performed in the stop-flow mode and extensive 2D NMR correlation experiments are measured. For unknown online determination the need for data is often mandatory. This type of information can be deduced from HSQC and HMBC indirect measurements and very recently it has been demonstrated that even direct measurements were possible in a crude plant extract. For this application the LC peak of interest was preconcentrated by trapping on SPE and the measurement was performed on a cryogenic flow... 

---