What should I do if my chromatogram encounters a leading edge peak?

 What should I do if my chromatogram encounters a leading edge peak?

✔ 01The influence of frontier peak

1️⃣ A. Calculation of impact peak height

When the peak areas are the same, their peak heights will differ greatly due to the peak front. This has an impact when we use peak height to calculate sample results, especially when calculating the minimum detection limit.

2️⃣ B. Calculation of peak area affected by

When calculating peak areas, the start and end points of the peak are generally determined by the slope of the chromatographic peak. At the front of the chromatographic peak, the flatter the front baseline, the more difficult it is to confirm the starting point, resulting in inaccurate peak area quantification.

3️⃣ C. Affects the confirmation of certain trace components

When the resolution of the previous peaks is not very good, the sample peaks will be easily hidden at the leading edge of the later peaks and cannot be calculated.

✔ 02. Cause analysis and solutions for frontier peaks

1️⃣ A. Column overload

Each chromatographic column has its maximum sample carrying capacity. When the sample amount is too large, overloading will occur, including mass overload and volume overload. We can see whether the peak shape is improved by reducing the sample amount or sample concentration. It can also be solved by increasing the column diameter and using a higher capacity stationary phase.

2️⃣ B. Improper selection of sample solvent

The leading edge peak occurs when the elution power of the sample solvent is much stronger than that of the mobile phase. Specifically, if the sample moves forward uniformly in the chromatographic column, we will usually get a normal distribution of peaks. When the sample solution reaches the chromatographic column in a relatively short time after injection and is not fully diluted by the mobile phase, due to the presence of a sample solvent with relatively strong elution ability, some samples are eluted faster and pass through the chromatographic column quickly, and finally Leading to peak front extension.

3️⃣ C. Chromatographic column damage

After long-term use of a chromatographic column, the silica gel packing will dissolve and the column bed will collapse, resulting in reduced column efficiency and leading to peak fronting. If it is found that the column is damaged, it is recommended to replace the column directly.

4️⃣ D. Peak interference

The two compounds co-elute, that is, a small peak appears before the large peak, and the chromatographic peaks are not separated. Interference can be reduced by adding sample purification procedures. The mobile phase can also be adjusted to improve resolution.