Distribution Craig counter-current

Two interlocking glass units for Craig counter-current distribution. 

Extraction scheme for a single solute by Craig counter-current distribution. (Figures represent the proportions in each phase for D= 1 and equal volumes. Only the first four extractions are shown). 

Table 4.6 Proportional distribution of a solute between extraction units for Craig counter-current distribution...

Figure 4.4. Two interlocking glass units for Craig counter-current distribution, (a) Position during extraction, (b) Position during transfer. (Note by returning the apparatus from (b) to (a) the transfer is completed. The mobile phase movos on to the next unit and is replaced by a fresh portion)...

Various unspecified samples of the sodium salt of heparin have been submitted to Craig counter-current distribution between an aqueous buffer solution and n-pentyl alcohol. Three fractions were obtained, two of which showed anticoagulant activity. 

Gregory, J.D., and L.C. Craig Counter-current Distribution of Gramicidin. 

Figure 4.1 illustrates a Craig counter-current distribution tube. Chamber C [Figure 4.1(a)] in each such tube is filled with solvent Z that is heavier than the extracting solvent S. The volume of solvent Z is small enough so that when the... 

Figure 4.1 A Craige counter-current distribution tube...

Equation (4.6) enables a calculation of the mean in this Craig counter-current distribution and Eq. (4.5) yields an estimate of the standard deviation in the distribution among Craig tubes. For example, let us return to our two solutes, 1,2-DCA and EG. Earlier, we established values for p and q from a knowledge of D or, in the limit of purely molecular partitioning, Kj). Let us find /r and a for both compounds after 100 transfers (i.e., r = 100) have been performed ... 

Pre-fractionation by Craig counter-current distribution requires more complicated apparatus . 

Craig, L. C. Identification of small amounts of organic compounds by distribution studies II Separation by counter-current distribution,... 

Liquid-liquid partition methods referred to in the previous chapter can be extended even to the separation of solutes possessing only small differences in their partition coefficients by a method called counter-current distribution. The technique of counter-current distribution, developed mainly by Craig, is a multiple partition process with a large number of stages, entirely discontinuous and stepwise in nature. 

King, T. P., Craig, L. C., Counter-Current Distribution, Methods Biochem. 

Multi-stage extraction using the ORSEP [95] is intended to mimic the procedure known as Craig extraction or counter-current distribution (CCD). As illustrated in Fig. 16, this technique provides a means of isolating and purifying a mixture of solutes by sequentially contacting the top phase of each chamber with the bottom phase from the adjacent chamber, in a manner that mimics counter-current extraction. 

A counter-current extraction is sometimes useful as a first step. For purification purposes a three-stage counter-current extraction between 70 % aqueous ethanol and petroleum ether is sufficient (1). Other systems have been used for the same purpose (11). Extensive separations of bile acids can be obtained with the counter-current distribution systems developed by Ahrens and Craig (37). 

---