The Methods of Initiating Reaction and their Time Ranges

Many complex-ion reactions are accompanied by a pH-change, and since the rate of these reactions is often pH-dependent, it is necessary to use buffers. A list of useful buffers for the pH region 5.5-11.0 is contained in Table 3.1.  

2- [N-Morpholino]ethanesulfonic acid (MES) Bis[2-hydroxyethyl]iminotris(hydroxymethyl)methane (Bis-Tris) Piperazine-N,N -bis[2-ethanesulfonic acid] (PIPES) 

3- [N-Morpholino]propanesulfonic acid (MOPS) N-[2-Hydroxyethyl]piperazine-N -[2-ethanesulfonic acid] (HEPES) N,N-bis[2-Hydroxyethyl]glycine (BICINE) 

Many of these are substantially non-nucleophilic and unlikely to effect the rate or course of the reaction, although this should always be checked. References 29 to 31 relate some problems in the use of some of these buffers. Occasionally, one of the reactants being used in excess may possess buffer capacity and this obviates the necessity for added buffer. The situation will often arise in the study of complex ion-ligand interactions when either reactant may be involved in an acid-base equilibrium. 

2 The Methods of Initiating Reaction and their Time Ranges 

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