Is this a limitation for this experiment?

I've done the beetroot biology practical assessment for OCR and I have the evaluative paper tomorrow. Trying to think of possible questions for revision, one common one is limitations.

Would using a standard solution to estimate the concentration of pigment in your solution be a limitation because it is not an exact measurement of how concentrated the solution is?

Or would the fact that we only did it once with no repeats be a better limitation to explain? (how would that affect results? i dont really understand)

any help appreciated! Thanks!

first one is not a limitation because you're using a standard solution through out your whole experiment i.e. you're using the same solution.

sorry i didn't make it that clear. We first made 5 solutions with different concentrations of red pigment. (so from colourless to dark red each labelled with a concentration)
Then we conducted the experiment, and compared our solution colour (which had an unknown pigment concentration) to these original 5 solutions, and were told to estimate which one it was most similar to.