Choice of Buffer Related to Bonded-Phase Stability

3 Choice of Buffer Related to Bonded-Phase Stability 

The type of pH modifier to make a desired mobile phase pH also has an effect on the column stability, and this is indirectly related to the peak efficiency and the retention of the analyte. As an increasing number of column volumes of the mobile phase are traversed through the column, the stability of the packing material could be comprised. Rearrangement of the packing bead leads to the loss of efficiency, dissolution of silica leads to loss in efficiency and retention, and hydrolytic decomposition of the bonded phase could impact the peak shape and retention. Different compounds, such as neutral compounds, acidic compounds, and basic compounds, could show different behaviors. 

Different types of buffers at the same ionic strength and wpH can have a significant impact on the dissolution of silica. The dissolution of silica is usually measured by the silicomolybdate colorimetric method [41]. When determining the bonded-phase stability using different run buffers (effect of buffer counteranion or countercation), the same H must be used. The H values (pH of the mobile phase aqueous -i- organic) may be different from the aqueous portion of the mobile phase and may obscure if the dissolution of the silica is directly related to the type of anion/cation and/or the pH. Generally, with the addition of organic solvents the pH of the mobile phase decreases for basic buffers and increases for acidic buffers (see Section 4.5 for more details). 

Generally, the lower the concentration of the buffer, the slower the dissolution rate of the silica. The rate of the dissolution of silica or the increase of 

With the phosphate buffer both components, basic amitriptyline and neutral toluene show poorer efficiency as the number of column volumes of mobile phase are passed through the column, indicating that the stationary-phase structure is becoming compromised (potential voids in the column). Moreover, if column voids are formed, it will effect the efficiency of all components 

---