Chromatography Forum

I tried by injecting several Fame standards separately dissolved in hexane to 1000 ppm, but all i got was the hexane peak. The height of the hexane peak of the first injection was at 120 uV, of the second injection was about 90 uV, of the third at about 60 uV and of the third at about 30 uV. There appeared only hexane peak at the first two injection, which was kind of separated into two peaks in the third and fourth injection. (The split of the hexane peak was way more obvious at the forth injection.)

That is weird. Some possibilites are the inlet split portioning valve is malfunctioning. There is a leak in the system somewhere possibly the inlet Check the column connections, perhaps the column broke in between the detector ferrule and the tip of the FID jet or perhaps it is merely leaky as many times graphite/vespel ferrules are used at the detector end and they are known to loosen after the first few thermal cycles. Try a few tests at lower concentration ~a few ppm splitless to eliminate the split valve, do a leak test, check the FID and ensure the gas flows are correct and it is not leaking, maybee the jet is plugged or in need of a cleaning. Take the end of the column off and dip in in methanol and check for correct bubbling or use a flow meter.