Question

When plotting a calibration curve to use for ion chromatography, would it be better to use peak area or peak height vs concentration ? Is the R-squared value a good basis for which to choose?

Answer 1

1) When plotting a calibration curve to use for ion chromatography, would it be better to use peak area or peak height vs concentration ?

Answer: It would be always preffered to use peak area Vs concentration

Peak Height: If in a chromatograph following things are observed then that chromatograph is called as ideal one.

i) symmetrical shaped peaks ii) well separated peaks from one another without overlap or shoulder bands and iii) non-noisy baseline.

In such type of chromatograph it is usually possible that height of each peak is in proportion to the amount of the particular component present in the sample mixture injected. Thus, if we observed an ideal chromatograph then it is on our choice to choose eigther peak height or peak area in quantitative calculations.

But this type of chromatograph is difficult to obtain each time because of following reasons:

• Impure sample
• Variation in parameters such as column temperature, flow rate of carrier stream, injection volume, etc.
• Variation in detector response due to nature and concentartion of compound
• Carry forward of residual impurities present from earlier sample

Thus, in such type of chromatographs it is difficult to apply peak height based calculations due to unsymmetrical peak responses and unstable baselines. Applying height based calculations will lead to errors in quantitative estimations due to few things such as i) close peaks are difficult to integrated in a reproducible manner ii) for asymmetrical peaks tailing is observed due to that difficult to integrated in a reproducible manner.

Peak area: In practice usually peak areas are used for quantitative analysis. Peak area calculations doesnt affected by distortioned or tailed of peak. To get high level of accuracy and precision it is advisable to use of peak area measurements for our calculation.

To chose whether peak height is better or peak area is better to consider is based on our judgement of the quality of the chromatogram.

2) Is the R-squared value a good basis for which to choose?

Answer: The R2 value will not decide whether height based or area based calculation should be followed.