Hi, use peak area, it should be proportional to the concentration in the sample. Peak height has the disadvantage that it depends on other variables such as pressure (the rate at which the compound is pushed through your column), the area compensates for this since for the same amount of material a reduction in peak height is compensated for by an increase in its width. Be aware that in any case (area or height) you need standards and their calibration lines to get to concentrations since the ionization of compounds and thus peak area/height may vary a lot, even between structurally very similar compounds.

I did use peak area for my calculations, Just needed QC & confirmation. Thanks a lot. Gerard J. M. Versteegh

Dear Majid,

Thanks for this nice question. You know now we are calculating height and /or area of peaks digitally, i.e. through using software like HP or MSD ChemStation, and so on.. In my small experience I think the important is to measure all peaks in a certain study using the same method, either height or area under the peak. I am using and preferring the area under the peak for calculating the parameters.

all the best

I like to point out that in isocratic elution mode; the peak height is strongly dependent on the retention time. So, if everything else is equal (concentration, mobile phase, temperature etc.) the faster the compound elutes the higher is the peak. The longer retained peak/s will on the other hand be correspondingly wider, which will compensate the decrease of peak height.

https://www.chromforum.org/viewtopic.php?t=8172

Hi you may use peak area consistently.

I think it is safe to use peak heights rather than peak areas to avoid coelution problems of some chromatographic columns Kenneth E. Peters .

The best choice for modern capillary-column chromatograms where peaks are well resolved is to use peak heights. When peaks show tailing or are poorly resolved, especially for older chromatograms based on packed column tecnology, peak areas might be a better choice. Most quantitative results allow you to compare peak-height and peak-area measurements and, in general, the results are quite similar.

you should not use peak height as peak height is dependent on sample amount and sometime when the sample concentration is very high, you may get a blunt peak in chromatogram.

if you are having a GC-MS just set some parameters while examining chromatogram and mass spectras. Try to have end members of a single peak and get the area of the peak for the selected end members.

By doing so, you will be able to correct the problem of tailing.

Most labs tend to report GCMS data from both peak heights and peak areas. Although I prefer to work with peak areas due to reasons indicated above, there are valid arguments for working with peak heights, such as co-elution issues. However, one might better optimize the chromatographic system to improve peak resolution. For example, the m/z 245 ion chromatogram for the identification of age diagnostic methyltriaromatic dinosteroids are fully resolved on a 60m GC column, while there are co-elution issues on a 30m GC column.

In order to apply QAQC parameters to assist in validating the results, the data obtained on a standard oil must fall within statistically defined permissible ranges (Norwegian Industry Guide to Organic Geochemical Analyses - by the Norwegian Petroleum Directorate). This is to ensure that geochemical results are interpreted in response to genetic processes and reflect natural compositional variation, rather than the effects of chromatographic separation (e.g. early breakthrough of mono-aromatic steroids with the saturated hydrocarbon fraction - add m/z 253 to the list of ions monitored for the saturated hydrocarbons) or variations in instrument performance (e.g. variations in relative response factors between internal standards and compounds of interest and their impact on concentration data, or where molecular parameters utilize more than one ion chromatogram such as the steroid aromatization parameter based on m/z 231 and 253 ion chromatograms).

Some of the learnings for applying QAQC parameters to validate geochemical data came from the methods used for viscosity measurement. Prior to performing viscosity measurements on heavy oil / bitumen samples, the viscosity of standard fluids with known viscosity (e.g. 10,600cP, 201,800cP and 1.56McP) are measured and the resulting viscosity data has to fall within 5% of the known viscosity to ensure the instrument is calibrated and the instrument is operating within nominal specifications. The same principles are applied to acquiring GCMS data, where the results for a known standard oil based on molecular parameters (e.g. Ts/(Ts+Tm) or concentration data (e.g. phenanthrene) must fall within statistical acceptance. For example, for a Peace River heavy oil standard, the permissible range for Ts/(Ts+Tm) = 0.29 - 0.32 with a most likely value 0.30. Meanwhile, the concentration of phenanthrene is 70 ppm and should remain so following repeated analysis, if the standard oil is stored under preserved conditions. However, dispersion from 70 ppm (typically due to variations in response factors relative to internal standard phenanthrene-d10) may be adjusted by applying the appropriate correction factor.

I use in general peak height, because sometimes conpounds elute very close next to each other and if you use area then you or the auto calculator combine 2 compounds by mistake but if you use peak height then you are sure you are using that specific compound so you are better...at least thats what i believe which i also see McCaffrey using peak height in on of his presentations because of the same reason

Majid, I just re-read your question, perhaps we need to clarify when to use GC-FID versus GCMS . In order to calculate Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios, I recommend using GC-FID (see also the Norwegian Industry Guide to Organic Geochemical Analyses), rather than GCMS, there can be quite a difference in ratios such as Pr/n-C17 when using GCMS. Although where biodegradation impacts these compounds, maybe GCMS helps with identification. Using the Norwegian standard oil (NSO-1) the Pr/n-C17 (peak area ratio ) following GC-FID falls within a permissible range 0.55-0.66, with a most likely value 0.6 If the ratio falls outside this range, the instrument or procedure requires maintenance and the NSO-1 is re-run. When I only have GCMS data, I calculate (only in desperation, with caveats) the Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios from the peak areas in the Total summed ion chromatogram or m/z 85 mass chromatogram. If Pr/n-C17 falls within the range 0.55-0.66, then I assume the response factors and instrument behaviour of the GCMS at least mimic the response of GC-FID. However, over the years I have found the Pr/n-C17 ratio for NSO-1 may fall outside the range 0.55-0.66, hence the preference for using GC-FID. Basically, the Pr/Ph, Pr/n-C17 and Ph/n-C18 ratios calculated from GCMS results are influenced by their relative response factors which may lead to increasing permissible range associated with the data.

The applications where peak heights are employed are typically for production allocation (or reservoir compartmentalization) based on high resolution GC-FID of whole oils. Basically, several thousand peak height ratios are calculated on the intra-paraffin peaks i.e. ratios of heights of neighboring chromatographic peaks (compounds). The methods are described in several papers such as Nouvelle and Coutrot, 2010. Org Geochem 41, 918-985 or Nouvelle et al., 2012. SPE-160812-MS.