PAH calibration problem

[mckrause]

Some questions:

1. Why are you limiting yourself to the average of response factors? This assumes a slope. Try fitting the data with a linear forced zero curve or a quadratic forced zero curve and see what happens. It is common, especially with SIM, to have non-linear responses over a calibration range.

2. 1.1 mL/min flow is pushing it for MS; even with the turbo. This is one of the reasons many of us have moved to smaller ID columns (20 m x 0.18, for example). You are below the optimum flow for your column, but the important thing here is your detector.

3. Your transfer line temperature is very important. You must maintain it high; for your temperature profile I'd have it set around 300 C.

[James_Ball]

Some questions:

1. Why are you limiting yourself to the average of response factors? This assumes a slope. Try fitting the data with a linear forced zero curve or a quadratic forced zero curve and see what happens. It is common, especially with SIM, to have non-linear responses over a calibration range.

2. 1.1 mL/min flow is pushing it for MS; even with the turbo. This is one of the reasons many of us have moved to smaller ID columns (20 m x 0.18, for example). You are below the optimum flow for your column, but the important thing here is your detector.

3. Your transfer line temperature is very important. You must maintain it high; for your temperature profile I'd have it set around 300 C.

The only problem with forcing zero in the calibration is that with some work, like EPA regulated samples, they frown on forcing zero in the calibration. Of course we all know that with modern instruments and software forcing zero should be an acceptable calibration, but the EPA is stuck in the last century on some things like that.