Missing peaks of IC4, IC5, NC4 & NC5 in natural gas sample

[arfeen66]

Sir we are using varian 450-GC for natural gas sample but last month we missed NC5 & NC4 peaks & now this month we missed out IC4, IC5, NC4 & NC5 peaks but when we run the STD sample these peaks are present, please give suggestions

thanks
M.Arif

[chromatographer1]

Your evidence indicates that the C4 + peaks are not present in your sample:

They do show up in your std.

They do NOT show up in your sample.

Ergo: they are not in your sample.

OR

Your sample is held in a manner where the higher hydrocarbons are dewed out, ie. they are changed into a liquid and do not pass through your sample system (transfer line) to your GC for analysis.

best wishes,

Rod