Question

What are some errors (not human) that can occur when using size and ion exchnage chromatography

Answer 1

Possibility of human error is more compare to any other possibility while performing exchange chromatography.

1.. Varying pH
Many chromatographers also use changes in pH to affect a separation. In cation exchange chromatography, raising the pH of the mobile phase buffer will cause the molecule to become less protonated and hence less positively charged. The result is that the protein no longer can form a ionic interaction with the negatively charged solid support, which ultimately results in the molecule to elute from the column. In anion exchange chromatography, lowering the pH of the mobile phase buffer will cause the molecule to become more protonated and hence more positively (and less negatively) charged. The result is that the protein no longer can form a ionic interaction with the positively charged solid support which causes the molecule to elute from the column.

2.. Selection of following things is very important

What Flow Rate to Use? What Buffer to Use? What pH to Use?

What Salt to Use for Elution?

3..Contamination

Ion chromatography is often used to target substances that exist in large quantities in the environment, such as chloride ions and sodium ions. Eliminating effects of contamination to perform high sensitivity analysis requires careful precautions, including handeling of　samples. Water obtained from laboratory ultrapure water systems has a resistance over 18 MO and contains almost no inorganic ions. However, even when analyzing such pure water, contaminants can result in detecting about several µg/L of chloride ions and other substances.
The 1 ppb (1 µg/L) peak detected in the chromatogram is equivalent to a 10^-9 g level in a 1 mL sample vial.