differential mobility spectrometry of ketones in air at extreme levels of moisture - air quality purifier

Under ten values of ambient pressure and water vapor concentration, the performance of the differential moving spectrometer was characterized from 1. 0u2009×u2009102 to 1.
7 × 10-04 ppm using the same origin series of seven ketone from acetone to 2-ketonedodecanone.
At 30 °c, the dispersion diagram of the separation field from 35 to 123td td shows that with the increase of the water level, the α function of the hydrated proton, the prime monomer and the proton-bound dimer increases
The increase in the water level is accompanied by a decrease in the quantitative reaction, and the formation of proton-bound dimer is first gradually suppressed, followed by a mass-reduced monomer.
Product ion of 2-
Xintong under 7 ppb was not observed above the moisture level of 4.
0 × 103 103 ppm to establish the limit for observing the formation of analyte ions.
The observation limit is from 1.
Month of acetone for 1 u2009 × 103 ppm.
7 months of 103 ppm-dodecanone.
These findings suggest that the ketone can be determined by differential transport spectrum (DMS)
In an analyzer near room temperature, in the event of an expected increase in humidity levels, a membrane inlet or top-air sampling of the surface or groundwater is used.
The moisture content in the DMS analyzer used as an environmental monitor should be maintained at 1.
0 u2009 × 103 103 ppm or less, a single ketone should be quantitatively studied at a fixed moisture level.
Differential Migration spectrum (DMS)
Is the ion migration spectrum (IMS)
Among them, ion properties and separation are due to non-
Linear relationship between ion velocity and electric field strength.
In DMS instruments, ions are carried through gaps formed by gas flowing through two parallel plates.
The electric field perpendicular to the plate in the gap is generated by the voltage of the asymmetric waveform.
The maximum amplitude of the waveform is called the separation voltage (SV).
The difference in the migration coefficient between the two extremes of the asymmetric oscillation electric field leads
Axial displacement and loss of ions when passing through the gap.
The center where the negative ion can be recovered and has been submitted to a probe electric field, compensation (CF)
, Superimposed on the oscillation field.
The analytical information of DMS instruments is included in the differential transport spectrum, that is, the dependence of ion current on CF.
Function diagram of ion abundance with separation field (SF)
CF is called a scatter diagram.
The dependence of the ion migration coefficient on the electric field can be described by a formula: where is the number density of the gas (
Number of molecules per cubic centimeter)
, Is the mobility measured under low field conditions, and α is a function that characterizes the dependence of mobility on the electric field.
Since the migration coefficient is sensitive to gas temperature, moisture, pressure and gas composition, these parameters should be controlled for the stable reliability of DMS and other migration analyzers.
The simplicity of DMS analyzer design and manufacturing encourages applications in chemical measurement, from air quality monitoring on the International Space Station to pre-monitoring
Filter ions before mass spectrometry.
The handheld DMS analyzer was developed for military use for the detection of chemical warfare agents, which demonstrates DMSfor's embodiment of the following requirements
On-site measurement.
In chemical analysis performed with DMS, substances are usually ionised in purified air or nitrogen by reaction with pioneer ions formed in the ionization region under ambient pressure.
In positive polarity, ionization of matter (M)
Occurs by placing a water exchange from a hydrated proton that forms a relatively simple product ion, usually a mass-modified monomer MH (HO)
Or proton binding dimer MH (HO).
This reaction can be known from studies using chemical ionization mass spectrometry (CI-MS)
, Atmospheric pressure ionization MS and IMS-
MS supporting moisture content in gas environments below 1 × 10 ppm.
Reactions to various substances are possible and can be extended using a variety of different ionization sources including radioisotopes, photoionization, and gas discharge.
The simple spectral pattern obtained from this ion source has achieved valuable analytical performance through relatively low resolution techniques.
The separation of ion peaks in DMS can in some cases enhance the analytical performance by adding a gas atmosphere of up to 1.
0 × 10 ppm of small polar molecules.
This substance, known as the steam modifier, increases the difference in the migration coefficient at the extreme of the asymmetric field, resulting in an increase in the separation of ion peaks in the compensation field.
In DMS, moisture can be considered a steam modifier.
DMS analyzer has the advantages of simplicity, size and low cost, and is also successfully supported by drift tube IMS instrument for monitoring water environment, which is used to monitor ammonia in surface water, halogen acetic acid in drinking water, sulfur four acid in groundwater and general environmental measurement.
Although some successful cases have been reported, environmental monitoring of water using DMS analyzers is still not common.
The interface with the water sample, such as the top empty sampler or the membrane inlet, may introduce moisture into the DMS.
A core issue of the present study plan is the effect of moisture on DMS response and performance, requiring quantitative description and management of parameters.
Previous studies in MS, DMS, and drift tube IMS have shown that an increase in moisture inhibits the response, although this can be reversed with an increase in temperature, particularly with Borsdorf's recent work.
Who systematically evaluated the effect of moisture increase on the ion peaks of the reactants in the ion migration spectrometer at 80 °c and up to 2 °c.
0x10 ppm moisture.
For aromatic compounds, the quantitative response to increased moisture levels decreased by> 90%, and the quantitative response to ketone decreased by> 70%.
Reaction to high proton-affinity Amine, 2-
Less than 10% of toluidine and replace aniline reduce.
In our DMS instruments, the temperature is limited to 40 °c as the analyzer stage is manufactured by a printed circuit board.
As part of a development project leading to a certain area --
Water monitoring instruments are deployed, so it is necessary to understand the quantitative impact of moisture on DMS response and performance.
The ketone is selected to benchmark the performance at a wide water level and to ensure that the proton affinity of the ketone is greatly improved compared to water, resulting in a favorable ionization chemistry.
The example of DMS selected by Finland for water monitoring is a prototype instrument from environ, capable of operating at room temperature at high humidity and can be applied to direct monitoring of aquatic environments.
The findings of this study will inform the design of the next phase to develop the inlet or interface of the water sample, as well as the moisture levels suitable for the reaction to volatile organic compounds.
The results of the effect of moisture on ketone ionization may also help to understand the DMS reaction to other analytes using atmospheric pressure ionization in positive mode.
The main purpose of our project is to develop AIMS2-
DMS detectors for environmental pollutant monitoring.
Suction module (AIMS)
In our research, some of the devices have not been studied, but its properties are promising for some applications.
One advantage of DMS relative to drift tube IMS is that the sample has good performance in wet air.
In DMS, changes in dispersion maps with different peak position or moisture content may provide quantitative information on the moisture content of the sample.
Since DMS analyzer is simpler and smaller than drift
Tube IMS analyzer, they are ideal for portable applications.