Chromatography Forum

We have recently purchased the Agilent NCD to perform nitrosamines. The detector displays an excessively noisy baseline. The Agilent engineer performed an IQ and OQ and his runs were also noisy. We have tried increasing the quality of the oxygen, replacing the insert, replacing the burner chamber quartz tube, varying the oxygen flow to the burner and ozone to the reaction chamber, ensuring that the peltier cooler is performing at -20 and have inserted a CTR filter in the transfer line. We have tried both the 10 V and 1 volt output from the detector. We normally run our GCs at 10 V but also lowered this to 1 Volt and still suffered noisy baseline. Has anyone else used this detector, suffered the same problem and what did you do to resolve this? Oxygen flow set at controller at 5 ml/min and temperature for burner at 450. We are using HP5, 30 m, .32 column with .25 u film thickness. Insert is dual-tapered with glass wool. Pressure at reaction chamber is 2.2 torr.

We have one here. I haven't used it, but I've seen some chromatography from it, and it is not all that spectacular in my opinion (i.e. the S/N for the LOD is about 1:1). I think the concentration of the low standard used is 1ppb.

Thank you for your reply. Using a 2 ul injection, we can achieve 5ppb PQL with a 5:1 signal to noise. Acceptable but integration is difficult due to the noise.

Well, I pulled up a small data set, and it looks like for:

N-Nitrosodimethylamine
N-Nitrosomethylethylamine
N-Nitrosodiethylamine
N-Nitrosodipropylamine
N-Nitrosodibutylamine
N-Nitrosopiperidine
N-Nitrosopyrrolidine
and
N-Nitrosomorpholine

the standard at 0.1 ppm has a S/N of 10 with a 3-5µL injection. I can certainly agree that the integration I am looking at has an essoteric quality to it...