Question

What are the components of a good buffer? What is the makeup of an optimal buffer?

Answer 1

The components of a good buffer include:-.

pKa

Most biological reactions take place at a pH between 6 and 8, so ideal buffers have pKa values in this range to provide maximum buffering capacity there. Most buffers work best at a pH within 1 unit of their pKa at 20°C. If you think your experiment will lower the environmental pH, then select a buffer with a pKa that’s just a little lower than your working pH. Likewise, select a buffer with a pKa slightly higher if you expect your experiment to raise your working pH.

Solubility

Buffers should be very soluble in water, and minimally so in nonpolar solvents (fats, oils, and organic solvents). This prevents the buffer from accumulating in cell membranes, vesicles and other nonpolar compartments in biological systems.

Membrane impermeable

A buffer should not readily pass through cell membranes—this also reduces the disproportionate accumulation of buffer in subcellular structures.

Minimal salt effects

Highly ionic buffers can cause problems or complications in biological systems. However, salts can be added to adjust the compound’s buffering capacity. Avoid citrate and phosphate buffers in reactions that are calcium-dependent (Tris also chelates calcium).

Influences on dissociation

Buffer concentration, temperature, and ionic strength (the measure of ion concentration) should have minimal impact on the dissociation of the buffer.

Ionic strength

This deserves special mention because you need to make sure your buffer doesn’t have much impact on the ionic concentration of your experimental milieu. Physiological ionic strength is between 100 – 200 mM of KCl or NaCl. Some buffers, like phosphate, can drastically impact the concentration of ions in a solution, while Good’s buffers generally don’t have that effect.

Cation interactions

If the buffers form complexes with cationic ligands, the complexes should be soluble. Ideally, at least some of the buffering compounds will not form complexes.

Stability

The buffers should be chemically stable, resisting enzymatic and non-enzymatic degradation.

Biochemical inertness

The buffers should not influence or participate in any biochemical reactions.

Optical absorbance

Buffers should not absorb visible or ultraviolet light at wavelengths between 230 nm and 700 nm. This prevents interference with spectrophotometric assays.

A buffer containing these all the properties in it or is having the most of the quantities is called an optimum buffer.

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