User Manual Version February 2014

STEP Ion Mobility Spectrometer

Sensortechnik und Elektronik Pockau GmbH Siedlungstraße 5-7 D-09509 Pockau, Germany Tel.: 037367 9791 Fax: 037367 77-730

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Table of content

1. Special Notes ........................................................................................................ 3

1.1 Power supply ............................................................................................. 3

1.2 Use appropriate fuse! ................................................................................ 3

1.3 Do not remove covering or front panel! ...................................................... 3

1.4 Working in explosive atmospheres ............................................................ 3

1.5 Electrical overload ..................................................................................... 3

1.6 Gas flow ..................................................................................................... 3

1.7 Use of dust filters ....................................................................................... 3

1.8 Change of the circulation filter ................................................................... 3

1.9 Radioactive source .................................................................................... 3

2. Description of STEP IMS ...................................................................................... 4

2.1 Introduction .................................................................................................... 4

2.2 Structure of the IMS ....................................................................................... 5

2.2.1 Gas part ................................................................................................... 5

2.2.2 IMS-detector ............................................................................................ 6

2.2.3 Electrical part ........................................................................................... 7

2.3 Applications .................................................................................................... 7

2.4 Resolution capacity of the IMS ...................................................................... 8

2.5 Minimal detectable concentration (MDC) ....................................................... 9

2.6 Interferences and how to avoid them ............................................................. 9

2.7 Overloading of the IMS ................................................................................. 10

2.8 Technical data .............................................................................................. 10

3. Operating instructions ....................................................................................... 11

3.1 control and connection elements .................................................................. 11

3.2 first start-up .................................................................................................. 12

3.3 Software “IMS CONTROL” ........................................................................... 14

3.3.1 Installation ............................................................................................. 14

3.3.2 Device communication........................................................................... 15

3.3.3 IMS Settings .......................................................................................... 17

3.3.4 IMS Measurement ................................................................................. 17

3.3.5 Loading substance files ......................................................................... 18

3.3.6 Substance analysis ............................................................................... 19

3.3.7 Save substances in the substance file .................................................. 20

3.3.8 RIP prosecution ..................................................................................... 21

3.3.9 Finish measurement .............................................................................. 21

3.3.10 Options ................................................................................................ 21

3.3.11 Automatic measurement functions ...................................................... 23

3.3.12 Opening and analysing IMS spectrum files ......................................... 24

3.3.13 Display a spectrum sequence ............................................................. 24

3.3.14 Program exit ........................................................................................ 25

3.3.15 Summary of program functions ........................................................... 26

4. Appendix ............................................................................................................. 27

4.1 Table of selected chemical substances ........................................................ 27

4.2 Certificate of the tritium radiation source of an IMS device .......................... 30

4.3 Abbreviations and technical terms................................................................ 31

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1. Special Notes

1.1 Power supply The power supply of the device is +19 up +21V.

1.2 Use appropriate fuse! Use only fuses which are specified for the device. The device could damaged.

1.3 Do not remove covering or front panel! Do not use the device without covering or front panel. Inside are high voltages

up to 2500Volt. Touching this parts can be very dangerous for your health.

1.4 Working in explosive atmospheres The standard version of the device is not equipped for the use in explosive

atmospheres.

1.5 Electrical overload Do not use voltages which are not specified for the device.

1.6 Gas flow The device soaks in ambient air with a flow rate of 40 ml/min. If the device

shall be used within other systems, this gas flow has to be guaranteed. Otherwise, there can be severe damage to the gas entrance system.

1.7 Use of dust filters The device can be equipped with a dust filter. The filter consists of

polypropylene with a Teflon-membrane, which protects the device from ingress of dust particles and liquids. The filter needs to be removed before a measurement is conducted to avoid distortions. The internal purging circuit is also equipped with a dust filter.

1.8 Change of the circulation filter The circulation filter of the device needs to be replaced after 6 month. The lifetime of the filter depends on the concentration of the measured substances and the frequency of measurement. The replacement will be conducted by STEP or authorised staff.

1.9 Radioactive source The detector cell of the device contains a weak radioactive source (see Appendix 4.2). The radiation does not penetrate the walls of the device. Do not open the detector cell.

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2. Description of STEP IMS

2.1 Introduction With the STEP IMS you received a device usable for the detection of a variety of toxic gases and vapours. It meets the increasing lawful demands regarding emission- and immission control of gaseous chemical substances. STEP IMS-Bio can be stationary and portable used for continuous process controlling in industry as well as analyzer for actual environmental pollution and the detection of hazardous materials. The principle of measurement is based on different drift velocities of ions within an electric field in air at normal pressure. Ambient air is directed to an ionization source and is ionized by weak radiation. Complex ions of type NH+, NO+, (H2O)n H

+ emerge that cause the positive reaction peak (RIP+) in the spectrum. Negative ions of types O2

- und (H2O)-m constitute the negative reaction peak (RIP-). Both types of ions are

always available in air. If there are pollutant molecules like phosphor-organic compounds or alkyl halides in

the air, a charge transfer between the reaction ions and the pollutant molecules

(which we denote M) takes place. Simplified, this can be written:

RIP++ M � RIP + M+ (positive mode)

RIP- + M � RIP + M- (negative mode).

Due to electric pulses at the entrance grid (figure 2), the ions are directed from the

radiation source to the drift tube. Depending on their physical features, ions move

with different drift velocity within the homogeneous electric field. Accordingly, ions

arrive at different times – their respective drift time – at the collector electrode and

cause an electricity signal. Because the drift time is individual, it can be used to

identify molecule ions M±, whereby the size of the signal at the collector electrode is

proportional to the concentration of these molecules in the air.

The collector signal is enhanced and digitalized. Data are processed by a 32-bit

microprocessor and transfer to the integrated microcomputer, which realized the

signal processing and show the spectrum an the measurement results on the display

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2.2 Structure of the IMS The structure of the device is schematically pictured in figure 1.

figure 1: schematic design of Ion Mobility Spectrometer

2.2.1 Gas part Entrance system The ambient air containing substance is continuously soaked in by a pump, is

directed to the entrance system and leaves it at the gas outlet. The air to be analyzed

is periodically or manually integrated into the internal gas circulation, which passes

the ionization source within the IMS cell. The cycle of sampling is process controlled

and can be varied in a wide range or automated by defined time windows.

Internal gas circulation The IMS exhibits an internal gas circulation. By a circulation pump, dry air is provided as drift gas (400 ml/min) as well as analysis gas (40 ml/min). The latter transports the sample from the entrance system to the ionization source. After passing through the measurement cell, both gas flows arrive at the circulation filter. Here, water vapour and the sample will be absorbed.

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Circulation filter The circulation filter can absorb water up to 10% of its dry matter. If humidity within the internal gas circulation exceeds 10ppm, the resolution of the spectrometer decreases. In case of continuous operation, the filter needs to be replaced after 6 months. The regeneration of the filter takes place at STEP. 2.2.2 IMS-detector Figure 2 shows the schematic structure of the IMS-detector.

Figure 2: schematic structure of the IMS-detector

Radiation Source The radiation source consists of a stainless steel base with an evaporated titanium

layer in which 100 MBq Tritium is absorbed. A SiO2-layer for additional wear

protection as well as a conductive aluminium layer are evaporated on top.

The radiation source is one of the electrodes of the IMS cell and causes ionization at

the contiguous gas layer. The entrance grid separates the ionization space and the

drift tube

Drift tube The drift cell is a tube of 5 cm in length and 10 mm in diameter equipped with

potential rings alternating with insulating rings. The electric field has a field strength

of 400 V/cm. At the end of the drift region, there is a collector electrode. It is

protected by an aperture grid and connected with the amplifier. The IMS cell, the

internal gas circulation and the circulation filter are a closed, gas-tight and compact

unit. The use of high-quality materials guarantees reliable electric function.

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2.2.3 Electrical part Amplifier The ion flow is amplified by an impedance transformer. The time constant is circa 50 µs and the amplification factor is 5*109 V/A. Pulse unit A particular pulse regime is used to improve resolution and sensitivity. The pulse width at the entrance grid is about 60 µs, the pulse height is 400 V. These pulses force 30-40% of the created ions into the drift region A/D-Converter The analogue signal from the amplifier outlet can be directly visualized by an oscilloscope. Each IMS-device exhibits 3 BNC-plugs to display signal, trigger pulse amd delayed trigger pulse. The analogue signal is digitalized with high resolution for further analysis. Microprocessor The internal control of the IMS is realized by a 32-bit ARM7 controller by Texas

Instruments. This Controller does the data collection, signal pre-processing and the

transfer of the data to higher-level computer systems.

Integrated microcomputer In the IMS a microcomputer (pITX) is integrated for controlling and signal processing.

2.3 Applications The charge transfer of molecules and air ions (see the reaction functions as described in 2.1) depends on the proton or electron affinity of the respective molecules. The higher the affinity, the lower is the detection limit of a molecule. The ions are identified by their mobilities. These ion mobilities depend on several characteristics of the molecules: mass, charge, charge distribution, cross section, structure, bonds etc. The mobilities in general also depend on temperature and pressure. The exact identification of a compound M is only possible if its ions result in a separate peak in the spectrum.

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Important application fields of the IMS for selected substances are given below: Chimney gases: Cl2, NH3, HCN, NOX, SO2, HCl Aldehydes: Formaldehyde, Acetaldehyde Halogens and I2, Br2, Cl2, F2, Methylchloride, Chlorobenzene, halogenated Phosgene, (Chloromethyl)methylether, hydrocarbons: Dichlorethen, etc. Isocyanates and Toluene 2,4-diisocyanate, Toluene 2,4-diamine, precursors: Phosgene, Chlorine Nitrocompounds: DNT, TNT and other explosives Chemical warfare Soman, Sarin, Tabun, VX, Mustard, N-Mustard, agents: Lewisite, HCN Aromates: Toluene, Xylene, Phenol, Aniline, Ethylbenzene Solvents: Acetone, Methanol, Ethanol, Phenol, Acrylonitrile,

Dimethylether, Ethylacetate, Butylacetate Semiconductor Diborane, Phosphine, Arsine Compounds: Bad smells: H2S, Mercaptans, Amines

2.4 Resolution capacity of the IMS The resolution R of a detector cell is defined by the relation between drift time of an ion and the peak width at half height tH. The peak width is the crucial parameter. It depends on the initial impulse width, the diffusion and repulsion of ions during the drift, as well as the space charge distribution. The resolution improves with increasing electric field strength. Based on the shape of the reaction peaks, the quality of the IMS cell is readily evaluable (figure 3).

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2 3 4 5 6 7 8 9 10 11 12

-0,5

0,0

0,5

1,0

1,5

2,0

2,5

3,0

3,5

4,0

U [V]

t [ms]

tH = 140 µs

Driftzeit tD

Figure 3: typical reaction ion peaks for positiv and negativ mode

2.5 Minimal detectable concentration (MDC) The detection of a chemical substance is limited by the fluctuations of the ion stream.

In general, a signal is still detectable if the signal amplitude is equal to the 3σ-value

of the ion current fluctuations. Based on that, the MDC’s of devices by STEP are

calculated. Concentrations are dimensionless given in part per billion (ppb) or part

par million (ppm). The conversion in a concentration with dimensions (mass per

volume) as µg/m³ or mg/m³ is readily feasible. For instance, the maximum work

allowable concentration (MAK) of hydrogen cyanide (HCN) is

ppbppmMm

mg

m

mllausäureMAK 90009

100010

4,22111110)B(

333==

⋅⋅

⋅=== .

2.6 Interferences and how to avoid them When mixtures of chemical compounds enter the ionization source, cross interferences may occur: the spectra of the single substances are changed due to interactions between the different ions. There are many analytical situations in which interferences do not play an important role. For instance, if one or several compounds with strong affinities have to be detected among others with weak affinities. However, the detection of a compound with weak proton affinity in a matrix of compounds with large affinities requires a previous separation by means of an additional gas chromatographic column. In this way, e.g., it is feasible to detect benzene in the presence of high toluene concentrations.

2 3 4 5 6 7 8 9 10 11 12

-3,0

-2,5

-2,0

-1,5

-1,0

-0,5

0,0

U [V]

t [ms]

tH =110 µs

Driftzeit tD

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2.7 Overloading of the IMS The input concentration of an IMS typically ranges from 1 ppb up to some ppm.

Overloading by high concentrations must be avoided!

As mentioned above, the IMS operation requests low water vapour concentrations in

the internal air flow, usually below 10 ppm. The sampling of very humid gases will

shorten the lifetime of the circulation filter and thus of the device.

2.8 Technical data

1. Dimensions 350 x 480 x 170 cm

2. Mass 7kg

3. Detectable gases, sensitivity see appendix 4.1

4. Display and signal outlet 7 inch Display, USB (PC), BNC-Buchse (Oszilloskop),

5. Alarms per definition

6. Measurement range 1000-times MDC

7. Warm-up time

8. Reaction time

9. Delay time

10. Temperature of operation 0 - 50 °C

11. Humidity 0 - 90 % relative humidity

12. Power supply +19 bis +21 V DC

13. Power consumption 35W/70W without/with heating

14. Ionization source see appendix 4.2

15. Data storage 160 GB hard drive, USB-stick

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3. Operating instructions

3.1 control and connection elements The main elements for control and connections are shown in the following figures 4

and 5.

frontpanel:

figure 4: control elements at the frontpanel of the IMS

1) IMS main switch

2) Switch heating detector

3) Switch heating valve

4) Gas inlet

5) Display

6) control-LED’s

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backpanel:

figure 5: Control and connection elements at the backpanel of the IMS

3.2 first start-up Befor starting you must notice the correct connections of the surrounding parts. The including power supply must connect to the port „Netz“, mouse and keyboard to “USB1” and “USB2” At port “USB” you must connect the including cable bridge between the USB-connectors type A and type B. With this bridge you connect the microcontroller with the internal microcomputer pITX. You can connect an extra PC to the connector type B for control the IMS without the using of the internal microcomputer. For this case you need an additional software-paket from STEP. The IMS-device can turn on at the main switch (figure 4). The circulation pump P1 and the microprocessor started. After initialization the IMS is in standby. This is shown by the control-LED.

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Heating of detector and induction valve is turn on with the switches 2 and 3 (figure 4). The default values are 20 degree Celsius. You can change these values later with the Software “IMS-CONTROL” (chapter 3.3.3). The 2 control-LED above the switches shows the correct function of the on-off-control for the heating. If they are gone of, the desired value for the temperature of detector and valve is reached. The internal microcomputer pITX can turn on with the switch “Standby” at the backpanel (figure 5). You can turn off the microcomputer with this switch, too. After booting the operating system “WindowsXP” you see the IMS-control interface at the display (chapter 3.3).

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3.3 Software “IMS CONTROL”

IMS CONTROL is used for controlling an IMS device as well as for data transmission, data analysis, visualization and recording IMS spectra. The program is developed for Windows operating systems 2000, NT, XP, Vista and 7. There are no special hardware demands. The data communication from control board to the integrated mini-PC of the stand-alone IMS is realized by an USB interface.

3.3.1 Installation

IMS CONTROL

IMS CONTROL does not need to be installed. It can be executed directly from USB stick or from a folder in which the ims.exe was copied. Note: The executable file ims.exe and the configuration file ims.ini must be copied in the same folder!

USB driver

Before the first run of the program the also delivered USB device driver „CDM20802_Setup.exe” must be executed with administrator rights in order to configure the USB interface to be a virtual COM port (USB Serial Converter). After successful installation and connecting IMS detector signal output with input of the mini-PC on the backside of the device via USB cable, your hardware manager should look similarly to figure 6:

Figure 6: virtual COM-port in the hardware manager

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Note: Be careful that the option „LoadVCP“ in the advanced device properties of the ‘USB Serial Converter’ is enabled!

3.3.2 Device communication

Connect the IMS detector signal output with input of the mini-PC on the backside of the device via also delivered USB cable. After starting ims.exe the program desktop in figure 7 appears. The following 4 steps are necessary in order to realize the device communication and data exchange. 1. In order to connect the IMS controller with the integrated mini-PC, press the Button „USB Configuration“:

The dialog „USB Configuration“ appears (figure 8). Here you can choose the appropriate USB port number which is given in your Windows Hardware Manager (see figure 6). 3. To make a connection with the IMS device, press the button „Open Port”

While opening the USB port, the also delivered device key is requested by the software (figure 8). If the device key is accepted, the connection will be completed and IMS CONTROL program will be activated. 4. The current USB port status is displayed (‘open/closed’). Leave the USB Configuration dialog with the “Close” button.

Having successfully fulfilled step 1 to 4, further configurations and control commands can be transmitted to the IMS controller.

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Figure 7: IMS CONTROL – main program desktop ’Spectrum’

Note:

All the position numbers in round brackets given in the following parts of this manual refer to the red marked numbers in figure 7.

Figure 8: Dialog ’USB Configuration’ with request of the IMS device key

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3.3.3 IMS Settings

Before the measurement, 3 IMS parameter must be set:

• HV (High Voltage) polarity (positive / negative)

• Temperature of detector

• Temperature of induction valve

High Voltage Polarity

The polarity of the IMS high voltage can be set with the selector at position (14). (pos=positive, neg=negative). Press the Button to confirm and affect the setting. A default delay time of 10 seconds is required for switching the IMS HV polarity. During the delay time the program is disabled to avoid faulty user inputs.

Temperature of detector and induction valve

The set point of the detector and induction valve temperature can be chosen with the arrow button at position (15), followed by pressing the right handed button.

Note: The temperature range for detector and inductor valve temperature is between 20 and 200°C.

3.3.4 IMS Measurement

Measurement start

A continuous measurement gets started by pressing the button at position (5). The spectrum is transferred from IMS controller to internal mini-PC via USB. In the diagram at position (20) the measured spectrum is displayed. Until the measurement is stopped

with the button, a new spectrum will be send periodically with a distance of around 1 second.

Graphical display of the IMS spectrum

The IMS spectrum is displayed in the unit Volt. It has a length of 2048 values with a time difference of 10µs. Thus, a spectrum length of 2048 values represents a measurement time per spectrum of 20,48 milliseconds. It can be chosen between the presentation as a function of time or alternatively in absolute points.

Control of induction valve and pumps

The induction valve and the pumps #1 and #2 can be controlled during running measurement with the selection points at position (16), (17) and (18).

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Saving IMS spectra

In the selection area “Options” at position (19) the measured IMS spectra can be saved by enabling the point “Save spectrum”. For this purpose a new folder will be automatically created which has the actual date in his name. The location of this folder

you can be chosen with the button at position (3). The default memory position is the folder where the ims.exe is located.

Spectrum analysis

By enabling “Spectrum analysis” at position (19) the peaks of the IMS spectrum will be calculated and highlighted in the graphic display at position (21) with coloured crosses. Essential peak parameters are presented in the table at position (24) of the ‘Peak Data’-tab:

� Maxima index

� Maxima value in Voltage,

� Peak width at half-height in µs and

� Peak area in µVs.

Important measurement and spectrum parameters are presented also in the info-box at position (24), e.g. temperature, pressure, flow, etc. (see figure 9).

Figure 9: IMS CONTROL - Tab ’Peak Data’

3.3.5 Loading substance files

By pressing the button at position (2a) a substance file can be loaded in the *.txt format. In the selection area (23) any substance stored in the file can be selected. The associated relative drift times of the typical substance peaks are shown in the editor field “Relative drift time to RIP”. The user can modify these values, add further peaks or delete peaks. The relative drift time td is calculated as:

RIPn

substntd

_

_= with

RIPIndexRIPn

peakcesubsIndexsubstn

−

−

_

tan_ (1)

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3.3.6 Substance analysis The substance analysis is slated to find typical substance peaks in the IMS spectrum, characterised by their relative drift time with reference to the RIP (see equation (1)). The analysis is chosen by enabling the option “Spectrum analysis” at position (19). The necessary settings can be made by the user in the selecting area “Substance Analysis” at position (22). They involve:

• Search window for the Reaction Ion Peak (RIP)

• Relative drift time of substance peak with reference to the RIP

• Tolerance width between nominal value and actual value of substance peaks and RIP (in points)

• Threshold value for the relative substance concentration related to the entire electrical IMS charge

Testing a substance sample for a specific substance in the database Relating to chapter 3.3.5, the name of the substance for which the sample has to be tested can be chosen in the selecting field ‘Substances’ (position (22)), where all the substance names stored in the selected database are listed. In the case of one or more substance peaks are found in the actual IMS spectrum, its relative concentration is shown in the diagram at position (23) in the ‘Substances’- tab (see figure 9). The relative substance concentration is defined as the substance peak area related to the sum of all peak areas in the spectrum. Note, the peak area is a measure for the electrical charge.

Figure 10: IMS CONTROL – Tab ’Substances’

The sensitivity of the IMS for displaying a substance can be changed by setting a threshold value for the relative substance concentration. That ‘C. Threshold’- parameter can be found in the area (22) corresponding to figure 7. The selected value corresponds to the minimum relative concentration value for which the program will consider a substance. A value of zero means maximum sensitivity.

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Testing a substance sample for all substances in the database

By selecting the option ‘Substancefile’ in the area (22) corresponding to figure 7, an unknown gas sample can be tested for all the substances stored in the selected database. If substances are identified, their relative concentrations are displayed with their actual and maximum value detected during the series of measurements in a form of a bar chart in the ‘Substances’- tab (see figure 11).

figure 11 : IMS CONTROL - Tab ’substances’

3.3.7 Save substances in the substance file

By pressing the button at position (23) a substance file can be selected in *.txt format, where the relative drifting times are stored together with the appropriate HV polarity and an user-chosen substance name. Note: The HV polarity is taken from the actual setting in the selection field at position (14).

figure 12: Dialogue – Save substance in database

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3.3.8 RIP prosecution

Manual RIP prosecution

By pressing the button the search window for the RIP is adjusted to the maximum peak in the spectrum. That maximum peak is set to be the RIP, which will be prosecuted inside the search window. Automatic RIP prosecution By selecting the ‘RIP auto’ option (see figure 13), the automatic RIP prosecution is enabled. The necessary search-parameter can be set in the configuration file ‘ims.ini’. Below you can see the corresponding section in the ims.ini: [IMS] Y MAX_RIP_DIFF=20 //maximum tolerance width (in absolute points) of the RIP position RIP_TEST=200 //number of measurements for periodically adjusting of the RIP search window SetRIP_V=1 //enable/disable the re-setting if RIP search window after opening the valve //(0-disable, 1-enable) D_RIP=10 //width of the RIP search window to the left and the right side

figure 13: Settings fort he RIP prosecution

3.3.9 Finish measurement

A measurement is finished by pressing the button at position (7). The induction valve is closed, pump #1 is set ton ‚on’ and pump 2 is set to ‚off“, which is the cleaning mode of the IMS.

3.3.10 Options

In the ‘Options’- tab of the program (see figure 14) different kinds of parameters can be set for signal processing:

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figure 14: IMS CONTROL – Tab ’Options’

RIP prosecution

Choosing ‚Window method’ means that the RIP will be searched within a search window as described in chapter 3.3.8.

Choosing ‘Adaptive method with p,T-correction’ means that the RIP search window and the RIP-position will additionally be corrected with respect to the actual pressure and temperature of the detector. Thereby external environmental influences like fluctuations in temperature or pressure can be compensated.

Relative concentration

Charge: The relative concentration of detected substances will be calculated with the area of the substance peak(s) related to the entire area of the spectrum. This means that the peak area is a measure for the electrical charge of the substance ions in the IMS reaction chamber.

Amplitude: The relative concentration of detected substances will be calculated with the ration of peak amplitude and RP amplitude.

Permissible peak half width

The procedure for peak detection tolerates peaks which have a half width within the determined range, limited by min and max value. Peaks which have a half width outside of this range will not be considered in the signal analysis.

With the button changes in the configuration file ‚ims.ini’ will be adapted to the analysis software without restarting the program.

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3.3.11 Automatic measurement functions

By pressing the button at position (11) some automatic measurement functions can be selected (figure 15).

Calibration measurement

For the calibration of substances it is necessary to measure them under the condition of constant defined concentration. Important data of characteristic substance peaks are saved in a separate file, optionally in .txt or .xls format for each measurement. The data to be saved include the peak position, amplitude, drift time related to the RIP, half width and peak area.

The measuring procedure is as follows:

1. Open the valve and start of measuring

2. With default setting, 10 measurements are preceded without data recording while the valve is opened in order to produce a constant substance concentration in the drift room of the IMS.

3. Then, 15 measurements are preceded (only when substance peaks are found!) with recording the calibration data and spectrum files.

4. The valve gets closed and recording of calibration data is finished.

Periodic valve switching With a free settable interval the induction valve of the IMS opens and closes periodically while measuring mode. Measured spectra are transferred to PC/Laptop and can be displayed and analysed.

Periodic polarity switching

In this mode the high voltage polarity periodically changes between positive and negative. The measurement time between polarity switching can be selected by the user freely. While switching the HV polarity the program is disabled for 30 seconds in order to avoid faulty user inputs.

In order to perform substance analysis the user can chose substance files for positive

and negative modes by pressing the button (see figure 15). The analysis software switches between positive and negative substance files with respect to the actual HV polarity. The same is true for the RIP search window, which can be set by the user for both HV polarities separately.

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Figure 15: automatic measurement functions

3.3.12 Opening and analysing IMS spectrum files

With the button an IMS saved spectrum file can be selected, displayed and analysed. The analysis includes the calculation and highlighting of peaks and a collection of essential peak parameters given in the table at position (24).

3.3.13 Display a spectrum sequence

With the button a folder with IMS spectrum files can be selected. Sequences of 10 spectrum files will be displayed in the diagram at position (20) with their time order to investigate the development of several peaks with progressive measurement time. Navigating with the left-right arrow keys at the right bottom of the diagram makes it possible to go to the next respectively to the former 10 spectrum files. Figure 16 shows a typical spectrum sequence.

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figure 16: Example for a spectrum sequence

3.3.14 Program exit

The button at position (13) exits the program IMS CONTROL. The USB port is closed and IMS is set into cleaning mode (flushing the measurement chamber). Note:

After finishing the measurement the IMS should never be switched off. It is recommended to leave the IMS in cleaning mode.

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3.3.15 Summary of program functions

Button Position Function

1 USB Configuration

2 Open and analyse IMS spectrum in *.txt format from folder Y

2a Load substance file in *.txt format

3 Select folder for saving IMS filesY

4 Print spectrum

5 Start measurement

6 Speed Cleaning

7 Finish measurement

8 Filtertest

9 Analyse spectrum

10 Display spectrum sequence from folderY

11 Automatic measurement functions

12 Program information (AboutY)

13 Close program

21 Status reports from IMS CONTROL

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4. Appendix

4.1 Table of selected chemical substances

Substance MDC (ppb)

Ionization

Alcohols

Butanol 10 β(+)

Cresol 10 β(+)

Cyclohexanol 10 β(+)

Ethanol 10 β(+)

Heptanol 10 β(+)

Methanol 20 β(+)

Tetrahydrofurfurylalcohol 10 β(+)

Alcanes

Cyclohexane 50 β(+)

Heptane 50 β(+)

Isooctane 50 β(+)

Nonane 50 β(+)

Aldehydes

Butylaldehyde 10 β(+)

Heptylaldehyde 10 β(+)

Propionaldehyde 10 β(+)

Amines

Amphetamine 1 β(+)

Diaminobutane 10 β(+)

Diaminobutane 10 β(-)

Diaminopropane 10 β(+)

Diaminopropane 10 β(-)

Dimethylformamide 1 β(+)

1,1-Dimethylhydrazine 1 β(+)

Dimethylurea 1 β(+)

Hexamethylentetramine 10 β(+)

Hexylamine 1 β(+)

Hydrazine 10 β(-)

Methylhydrazine 1 β(-)

Methylhydrazine 1 β(+)

Nicotine 2 β(+)

Nonafluorobutylamine 1 β(-)

Aromates

Chlorophenol 10 β(-)

Dimethoxybenzene 10 β(+)

Ethylbenzene 5 β(+)

Iodobenzene 10 β(-)

Nitrobenzene 10 β(-)

Phenol 10 β(-)

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Substance

Substance MDC (ppb)

Ionization

Carbonic acids

Acetic acid 10 β(+) (β(-)

Formic acid β(-)

Esters

Ammoniumacetate 1 β(+)

Ethylacetate 1 β(+)

Ethylacetoacetate 1 β(+)

Phthalic acid diethylester 1 β(+)

Phthalic acid dibutylester 1 β(+)

Phthalic acid dioctylester 1 β(+)

Ethers

Diethylether 1 β(+)

Divinylether 1 β(+)

Halogenated hydrocarbons

Amylchloride β(-)

Amylchloride β(+)

Chlorbromomethane β(-)

Chloroacetonitrile β(-)

Chlorotrimethylsilane β(-)

Chlorodimethylether 5 β(-)

Dichlorethane 5 β(-)

Dibromethane β(-)

Dibromobutane β(-)

Dibromomethane β(-)

Dibromopropane β(-)

Isobutylchloride β(-)

n-Butylchloride β(-)

Methylchloride 1000 β(-)

Trichlorethylene β(-)

Trichlorfluoromethane β(-)

Vinylchloride (VC) 100 β(+)

Ketones

Acetone 1 β(+)

Acetophenone 1 β(+)

Acetylacetone β(+)

Acetylacetone β(-)

Benzophenone β(+)

Cumene ß(+)

Ethylmethylketone 1 β(+)

Hexanone β(+)

Phosphor organic compounds

Malathion β(+)

Tributylphosphite 1 β(+)

Tricresylphosphate 3 β(+)

Pyridines

Pyridine 10 β(+)

2-Dimethylpyridine 10 β(+)

29

Substance MDC (ppb)

Ionization

Others

Acroleine β(+)

Ammonia 1 β(+)

Dibutylsulfite β(+)

Carbon disulfide 5 β(-)

Chlorine 10 β(+)

Diborane 10 β(-)

Ethylenoxid 100 ß(+)

Hydrochloric acid 25 β(-)

Hydrocyanic acid 5 β(-)

Hydrogen sulfide 10 β(-)

Nitric oxide 50 β(-)

Nitrogen dioxide 5 β(-)

Phosgene low high

0,5 100

β(-)

Sulfur dioxide 10 β(-)

Sulfur hexafluoride 10 β(+)

Remarks:

1) MDCs are valid for compounds in synthetic air at 20 °C. 2) Further substances can be measured if required.

30

4.2 Certificate of the tritium radiation source of an IMS device

Certificate

of the tritium radiation source of an IMS device

IMS device No.: ………………

Source name: H-3, No. ……

Source type: quasi-enclosed radioactive substance

Activity: ≤ 100 MBq

Reference date: …………

Radiochemical: no radioactive reaction product;

inactive 3He will be formed

Radiation type: β- emission

Radiation energy: medium energy 5.68 keV

maximum energy 18.70 keV

Half life period: 12.4 years physical 10 days biological, in terms of 3H2O

Bremsstrahlungs-dose rate

constant: 9.9*10-9 mSv h-1 GBq-1 (at a distance of 1 m)

Equivalent dose: < 0.1 mSv cm2 h-1 kBq-1

Weakening/Decrease of radiation: air: 1 mm; water: 1 µm; tissue: 6 µm

Location and assembly: fixed inside of the IMS device;

The radiation source is scoop-proof assembled and not accessible from the outside.

Local dose rate: < 0.5 µSvh-1 at a distance of 0.1 m of the touchable surface of the

measuring device

Source description: The construction of the radiation source is accessible at the producer (technical drawing No. RID3.57-02:04) if required. The tritium is

bound in form of titaniumtitride and shielded with silicium and aluminium layers for protection.

……………….. Date / Signature

31

4.3 Abbreviations and technical terms

Abbreviations and technical terms

Meaning

Dimer complex consisting of two identical molecules

IMS Ion Mobility Spectrometer

FWHM full width at half maximum

LED light emitting diode

MDC minimal detectable concentration

Monomer single molecule

n/a not available

ppb parts per billion (10-9

)

ppm parts per million (10-6

)

RIP reaction ion peak

SPS memory programmable control

TMonomer, Dimer, RIP drift time of monomer, dimer or reaction ions

UV ultraviolet (radiation)

V DC Volt, direct current

ß beta radiation (fast electrons)

ß(-) ionization by a tritium radiation source, negative mode

ß(+) ionization by a tritium radiation source, positive mode