Question

Suppose I am running a collection of samples on a chromatograph (gas or liquid) in some order. Some of the sample molecules have large retention times due to their size and/or interactions with each other or the stationary phase to such an extreme extent that molecules from the previous sample are still arriving at the detector while molecules from the current sample are arriving at the detector.

What is this problem called? Is it an example of carryover, or would some other term better apply? Or would it be termed contamination? Or something else?

Answer 1

The problem described is called carryover in chromatography, where molecules from a previous sample contaminate the analysis of the current sample. It can lead to distorted or overlapping peaks in the chromatogram. Strategies to address carryover include system cleaning, blank runs, and optimizing chromatography conditions.

Step-by-step explanation:

The problem you described, where molecules from the previous sample are still arriving at the detector while molecules from the current sample are arriving, is called carryover in chromatography.

Carryover occurs when there is inefficient removal of the previous sample from the chromatography system, leading to contamination or interference with the analysis of the current sample.

This can be particularly problematic when analyzing samples with molecules that have large retention times. It can result in distorted peaks or overlapping of peaks in the chromatogram, making it difficult to accurately identify and quantify the components of the current sample.

To address carryover, various strategies can be employed including thorough cleaning of the chromatography system between samples, using blank or solvent runs to flush out any residual sample components, and optimizing the chromatography conditions to minimize interactions with the stationary phase.