Reference materials at emission levels of NH3 and HCl.

Due to instability in static mixtures, in the past only dynamic preparation techniques for mixtures of NH3 and HCl were maintained; however, recent developments of new passivation techniques for cylinder treatment and commercially available nitrogen with a very low content of impurities have opened up the possibility of preparing stable mixtures in cylinders by gravimetry. Mixtures of NH3 (300 microL/L and 30 microL/L) and HCI (300 microL/L) were prepared in nitrogen in cylinders with different passivation treatments. The mixtures were compared with dynamically prepared mixtures using Photo Acoustic detection (PAS) and FT-IR. The uncertainty is about 3.5% with PAS analysis for NH3 at the 300 microL/L level. For the analysis of HCI with FT-IR the initial uncertainty in the 300 microL/L mixtures is about 7%. Two of the HCI mixtures show significant instability; for the other three mixtures the uncertainty in the measurement is too large to discriminate between stability and instability. The NH3/N2 mixtures are stable within 3.5% for a one-year period. The stability of the 30 microL/L mixtures of NH3 cannot be underpinned by measurement results, but a systematic effect in the measurement procedure seems more likely than instability. Improvement in the measurement procedure should clarify this point.

Comparison between collision induced dissociation of electrosprayed protonated peptides in the up-front source region and in a low-energy collision cell.

A systematic comparison between the up-front Collision induced dissociation (CID) mass spectra and low-energy CID tandem mass spectra from twenty-one singly and/or doubly charged peptides has been made. CID spectra of the peptides were recorded at different electrode voltages in the up-front source region of a single quadrupole instrument and different collision energies in the collision cell of a tandem quadrupole instrument. It was observed that up-front CID and low-energy CID yielded comparable product ion spectra from protonated peptides, and that the instrumental settings necessary for obtaining comparable CID mass spectra from the two methods are correlated.