Simultaneous concentration and

On the other hand, its should be emphasized that such basic analytical properties as precision, sensitivity and selectivity are influenced by the kinetic connotations of the sensor. Measurement repeatability and reproducibility depend largely on constancy of the hydrodynamic properties of the continuous system used and on whether or not the chemical and separation processes involved reach complete equilibrium (otherwise, measurements made under unstable conditions may result in substantial errors). Reaction rate measurements boost selectivity as they provide differential (incremental) rather than absolute values, so any interferences from the sample matrix are considerably reduced. Because flow-through sensors enable simultaneous concentration and detection, they can be used to develop kinetic methodologies based on the slope of the initial portion of the transient signal, thereby indirectly increasing the sensitivity without the need for the large sample volumes typically used by classical preconcentration methods. 

JA Singleton, LF Stikeleather. High performance liquid chromatography analysis of peanut phospholipids. I. Injection system for simultaneous concentration and separation of phospholipids. J Am Oil Chem Soc 72 481-483, 1995. 

Lemoine, F Wolff, M., and Lebouche, M., Simultaneous concentration and velocity measurement using combined laser-induced fluorescence and laser Doppler velocimetry Application to turbulent transport. Exp Fluids 20,319 (1996). 

Desalting is mostly carried out while keeping the feed volume constant, i.e., by replenishing the liquid lost in the filtrate. Therefore the protein concentration in the feed is also maintained constant. Exceptions are where simultaneous concentration and desalting are carried out. 

Recently, Hawthorne et al. coupled the ASE technique to solid-phase extraction using sorption discs that were placed in the extraction chamber together with the sample in order to simultaneously concentrate and extract polar compounds such as acid herbicides and their esters from soils, using strong anion-exchange (SAX) discs [99]. They also used this combined methodology to develop a convenient method of shipping extracts from field sites to the analytical laboratory [100]. In the former application, the esters of the... 

Good agreement was achieved between the experimental results and the solutions calculated with the above empirical isotherm equations. The simultaneous concentration and separation of the two feed components was achieved by gradient elution. Figure 15.10 compares the experimental and calculated results obtained with a linear gradient of 10 to 40% ACN in 20 minutes, with a 2.4 mL feed... 

As we have described, TGF has successfully demonstrated the simultaneous concentration and separation of a wide range of species in a variety of implementations. Key figures of merit for TGF as a separation modality are the concentration factor and peak capacity. Static TGF, where the externally applied pressure remains constant, has demonstrated concentration factors in excess of 20,000 but is limited to peak capacities <10 [56], As a result, there has been recent work to develop a dynamic form of TGF called scanning TGF [67], where the externally applied pressure is varied with time. This technique allows higher peak capacity and tunable resolution and concentration by adjusting the rate at which the procedure scans through the applied pressures. 

Balss, K.M., et al., Simultaneous concentration and separation of enantiomers with chiral temperature gradient focusing. Anal. Chem., 2004, 76 7243-7249. 

An elegant variant of this procedure is known as the Baker-Williams method. In this method, the chromatographic column is also surrounded by a thermostated heating jacket which ensures that an adequate thermal gradient is maintained. The separation efficiency is enhanced by the simultaneous concentration and temperature gradients. 

The earhest application of membrane processes in the food industry and one of the largest is in the dairy industry where it is used for (a) the pre-concentration of milk for cheese manufacture and (b) the fractionation of cheese whey. Milk is a complex liquid consisting of 12.5 wt% total solids, 3.3% protein, 3.5% fat, 4.9% lactose and 0.7% ash. RO of cheese whey was commercialised in 1971, and the first UF/RO plant for fractionating cottage cheese was commercialised in 1972. By 1996 approximately 80,000 m RO and 240,000 m UF membrane area was installed for dairy processing [22], of which whey processing constituted 75%. In 1984 NF was introduced for simultaneous concentration and desalination. 

Basmadjian, D., 2004. Mass transfer principles and applications. CRC, Boca Raton. Bengtson, G, Scheel, H., Theis, J., Fritsch, D., 2002. Catalytic membrane reactor to simultaneously concentrate and react organics. Chemical Engineering Journal 85,303-311. 

Ultrafitration is a rapid and protective technique, by which a P. solution is simultaneously concentrated and freed from small molecular contaminants. It is usually operated with excess, rather than reduced pressure. By using the appropriate membrane filter (pore sizes range from 15 pm upwards), P. mixtures can also be crudely fractionated according to M,. Biologically active P. can be prepared on an industrial scale by using tubular membranes with large surface areas and a daily throughput eapaeity of several thousand liters. 

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