We currently use a 7890 with a NPD for the analysis of Acrolein according to OSHA 52. During a recent run, we noticed a much larger solvent peak (toluene) and a much smaller derivatizing agent peak (2-(hydroxymethyl)piperidine). It seems like the detector's sensitivity to nitrogen compounds has decreased quite a bit and it's sensitivity to hydrocarbons has increased. We've tried changing the Blos bead but saw no change. The offset is set to ~20 and we're able to get that with a voltage of ~0.85 V. The gas supply seem fine, none of the indicating purification traps show any signs of breakthrough. Anyone have any ideas on why I'm seeing this sensitivity change? Thanks.
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