How do you know they are too small? Don't compare them to the solvent peak, because your solvent's concentration is hundreds or thousands times higher than your standards. They could be normal size. To check this, make serial dilution and inject all of the points of a proposed calibration curve to see if you can still make a cal. curve with proper linearity.

Hi Mukhtar,

The area for 30ppm conc is 0.0040, 0.0043 and 0.0046 for C14, c15 and c16 respectively.

Can be seen in attached pictures.

Is it normal? I mean signal to noise ratio is very low.

Optimize the fuel (hydrogen) to oxidizer (air) ratio of the FID to ensure the best response for your analytes; typically, start with a 10:1 ratio and adjust the fuel gas in steps of +/- 5 mL/min. https://www.chromatographyonline.com/view/optimizing-sensitivity-gc-fid-analysis

Insert the calibrated digital thermometer from topside by piercing glass wool. Set column oven temperature on GC to 50°C, 100°C, 200°C, and 250°C. Allow to stabilize the set temperature for 5 min and record temperature on the digital thermometer at respective temperatures. Frequency: Once in three months. https://www.pharmaguideline.com/2010/11/gc-calibration.html

An FID uses a flame to ionize organic compounds containing carbon. Following separation of the sample in the GC column, each analyte passes through a flame, fuelled by hydrogen and zero air, which ionises the carbon atoms https://www.peakscientific.com/discover/news/how-does-an-fid-work/

The Essential Guide to Optimizing Sensitivity in GC–FID Analysis https://www.chromatographyonline.com/view/essential-guide-optimizing-sensitivity-gc-fid-analysis

Hi

The analysis and calculations protocols are well explanined in the following paper:

https://doi.org/10.1007/s12161-021-02203-0

I hope this helps!