The Analysis of a Selection of Small Peptides

The technique of isotachophoresis has not been used extensively for the analysis and separation of peptides as both peptides and amino acids can be very effectively separated by other techniques. However isotachophiresis can be used for the separation of peptides and an example is given in figure 29.

Figure 29. The Analysis of Some Small Peptides

The terminating electrolyte was L(-)-alanine which was adjusted to a pH of 9.8 with barium hydroxide. The leading electrolyte ion was 5-bromo-2,4-dihydroxy benzoic acid at a concentration of  0,004M and adjusted to a pH of 9.05 by the addition of lysine. A constant current of 100micro-amps was used to develop the separation, which took about eight minutes. The sample consisted of 0.01 milli-moles of glutathione, glycineglycine hydrochloride, glycylglycylglycylglycine and D-leucyl-L-tryrosine. It is seen the chloride ion is more mobile than the 5-bromo-2,4-dihydroxy benzoic acid and has passed the first separation boundary It is clear that from the linear traces of both the conductivity detector and the UV absorption detector that the concentration of the leading electrolyte is not changed after the passage of the more mobile chloride ion.