The effect of humidity on sensitivity of amine detection in ion mobility spectrometry.

Vaporized water molecules are unavoidably present in every ion mobility spectrometry (IMS) measurement. In general, this humidity is seen in positive mode IMS-spectra as protonated water clusters producing reactant ions. Clusters containing water molecules are also abundant among ions generated by an analyte. In this paper the influence of humidity on IMS-spectra was systematically investigated and determined by measuring different concentrations of a selected amine at various levels of humidity. The selected amine, trimethylamine (TMA), was chosen as the model analyte due to its atmospheric importance. During the measurements, surplus water vapor was introduced into the drift section inside the IMS instrument; the concentrations of both amine and water were adjusted by controlling the gas flows. The simultaneous presence of water vapor and analyte at various predefined concentrations revealed the sensitivity of the IMS-technique to water and the effect of moisture on the ion mobility distribution. The results indicated that the existence, positions and shapes of the peaks are strongly dependent on the amount of moisture. However, the sensitivity of detection is weakly dependent on humidity if this detection is based on monomer ion peak or the sum of peaks generated by the analyte, In addition, the main principles of the adjustment of sample and water concentrations are presented here.

Liquid flame spray for generating metal and metal oxide nanoparticle test aerosol.

A flame-based method for generating nanoparticles with production rate in the order of g/min is presented to be used in a variety of applied studies concerning nanoparticle measurements and toxicological tests. In this study, ferric oxide, titanium dioxide, and silver nanoparticles were produced by this technique, as an example of the variety of producible compounds, and number and surface area were measured by state-of-art aerosol instruments. In the primary experiments of this study, the generator was used in a conventional way, in a fume cupboard, and the aerosol was measured from the exhaust duct of the cupboard. It has been shown that this steady, turbulent flame generator is also suitable for producing high-concentration aerosols in a wider concept. The generated aerosol was measured by variety of aerosol instrumentation to show the applicability of the generator. When using the generator intentionally as a source of aerosol in the flame processing room, mean nanoparticle sizes of 5-60 nm and active surface area concentration ranges of 1-10,000 microm(2)/cm(3) were covered for the room aerosol.

Adjusting mobility scales of ion mobility spectrometers using 2,6-DtBP as a reference compound.

Performance of several time-of-flight (TOF) type ion mobility spectrometers (IMS) was compared in a joint measurement campaign and their mobility scales were adjusted based on the measurements. A standard reference compound 2,6-di-tert butylpyridine (2,6-DtBP) was used to create a single peak ion mobility distribution with a known mobility value. The effective length of the drift tube of each device, considered here as an instrument constant, was determined based on the measurements. Sequentially, two multi-peaked test compounds, DMMP and DIMP, were used to verify the performance of the adjustment procedure in a wider mobility scale. By determining the effective drift tube lengths using 2,6-DtBP, agreement between the devices was achieved. The determination of effective drift tube lengths according to standard reference compound was found to be a good method for instrument inter-comparison. The comparison procedure, its benefits and shortcomings as well as dependency on accuracy of literature value are discussed along with the results.