1 Reply Latest reply on Dec 13, 2018 4:57 AM by james_jenkins

    NPD Sensitivity Change


      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.