Field flow fractionation, optimization

Manh Thang, N., Geckeis, H., Kim, J. I., and Beck, H. P. (2001). Application of the flow field flow fractionation (FFFF) to the characterization of aquatic humic colloids Evaluation and optimization of the method. Colloids Surf. A 181(1-3), 289-301. 

Another use of cell disruption as a step in the analytical process is for obtaining a suspension of single cells — that can be used under optimal fermentation conditions — by ultrasonic disruption of cells manufactured in active dry wine yeast. Their potential was confirmed by comparing the elution profiles of non-sonicated and sonicated yeast sample dispersions obtained using two different field flow fractionation techniques [88]. 

Giddings, J.C. Optimized field-flow fractionation system based on dual stream splitters. Anal. Chem. 1985, 57, 945. 

Field flow fractionation (FFF) can also be used for microbial cell separation. In the FFF technique, a field (may be gravitational, centrifugal, thermal-gradient, electrical, magnetic, etc.) is applied perpendicular to the fluid flow, causing particles to migrate with different velocities. Fields of sedimentation, diffusion, and electrical diffusion are manipulated to optimize the separations of microbes. Separation of Pseudomonas putida and E. coli has been achieved by hyperlayer FFF. Fractions of the whole cells were collected after the separation at different time intervals, dif-... 

Arakawa, T., Philo, J. S., Ejima, D., Sato, H. and Tsumoto, K. Aggregation analysis of therapeutic proteins. Part 3. Principles and optimization of field-flow fractionation (FFF). Bioprocess Intern. 5 52-70, 2007. 

Most laboratory experiments demonstrating the utility of EO transport of organic compounds were conducted with kaolinite as the model clay-rich soil medium. Shapiro et al. (1989) used EO to transport phenol in kaolinite. Bruell et al. (1992) have shown that TCE can be transported down a slurry column by electroosmotic fluid flow, and more recently, Ho et al. (1995) demonstrated electroosmotic movement of p-nitrophenol in kaolinite. Kaolinite is a pure clay mineral, which has a very low cation exchange capacity and is generally a minor component of the silicate clay mineral fraction present in most natural soils. It is not, therefore, representative of most natural soil types, particularly those which are common in the midwestem United States. The clay content can impact the optimization and effectiveness of electroosmosis in field-scale applications, as has recently been discussed by Chen et al. (1999). 

Fig. 4 Optimized SdFFF fractogram of ES Cells. Representative fractogram of ES cell suspensions after SdFFF elution. Elution conditions Flow injection of 100 pL of ES suspension flow rate, 0.6 mL/min (sterile PBS, pH 7.4) and external multigravitational field, 40 (O.lg spectrophotometric detection at 254 nm). Fractions were collected as follows PFl, 3 min 40 sec/4 min 15 sec PF2, 4 min 20 sec/4 min 50 sec PF3, 5 min 0 sec/5 min 50 sec. ER corresponds to the end of channel rotation. In this case, the mean externally applied field strength was equal to zero gravity thus RP, a residual signal, corresponds to the release peak of reversible cell accumulation wall sticking. (View this art in color at www.dekker.com.)...

Equation (7) is a very important relationship because, with respect to Eq. (4), it indicates that in the most practical range of the linear flow velocities, above the optimal flow, the efficiency of the separation in FFF increases very rapidly with the retention ratio. This is rather an exceptional case among separation methods and the importance of this behavior has to be regarded with respect to the fact that the FFF methods and techniques are especially convenient for the fractionation of large and polydisperse species, such as macromolecules and particles. As the retention usually increases with the molar mass or particle size in polarization FFF, the efficiency is higher in the high molar mass or large particle size domain. This is one of the reasons why the FFF methods are particularly competitive in this field of application. 

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