HPLC - Why do my chromatograms show tailing peaks, ghost peaks, front peaks, split peaks/shoulder peaks, or round peaks?
There are several reasons that might cause tailing peaks: Mass overload – When a smaller sample amount (mass) is injected, the peak tends to become more symmetrical or split into two separate peaks. Using a more diluted sample for injection can correct this issue. Secondary interactions – When neutral compounds (such as acetophenone or toluene) are injected, the peaks become symmetrical. Adjusting the pH of the mobile phase can neutralize charged analytes. For columns with larger internal diameters (>10 mm), radial temperature gradients can also lead to peak tailing. To avoid such problems, the use of a column oven is recommended. Additionally, tailing may result from irregularities during column packing, voids at the column inlet, or partially blocked inlet frits causing irregular flow distribution/pathway. Ghost peaks often originate from late elution of analytes from previous injections, column contamination, improper sample preparation, or mobile phase contamination. Fronting is typically indicative of column overload, improper column packing, or uneven silica bed density. Generally, using a lower slurry density solvent for the slurry and packing solvents, along with less gel, to pack these columns will resolve the issue. Peak splitting or shoulder peak is usually caused by voids at the column inlet or partially blocked inlet frits (not necessarily causing increased pressure) and the disruption of sample paths as the sample passes through multiple pathways within the column. This phenomenon can also occur when the column is poorly packed and the packing bed settles under system pressure or when the mobile phase pH is too high, dissolving silica and creating voids at the column inlet.
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